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Estradiol prevented intestinal ischemia and reperfusion-induced changes in intestinal permeability and motility in male rats

Abstract

OBJECTIVES:

Ischemia and reperfusion (I/R) in the intestine could lead to severe endothelial injury, compromising intestinal motility. Reportedly, estradiol can control local and systemic inflammation induced by I/R injury. Thus, we investigated the effects of estradiol treatment on local repercussions in an intestinal I/R model.

METHODS:

Rats were subjected to ischemia via the occlusion of the superior mesenteric artery (45 min) followed by reperfusion (2h). Thirty minutes after ischemia induction (E30), 17β-estradiol (E2) was administered as a single dose (280 μg/kg, intravenous). Sham-operated animals were used as controls.

RESULTS:

I/R injury decreased intestinal motility and increased intestinal permeability, accompanied by reduced mesenteric endothelial nitric oxide synthase (eNOS) and endothelin (ET) protein expression. Additionally, the levels of serum injury markers and inflammatory mediators were elevated. Estradiol treatment improved intestinal motility, reduced intestinal permeability, and increased eNOS and ET expression. Levels of injury markers and inflammatory mediators were also reduced following estradiol treatment.

CONCLUSION:

Collectively, our findings indicate that estradiol treatment can modulate the deleterious intestinal effects of I/R injury. Thus, estradiol mediates the improvement in gut barrier functions and prevents intestinal dysfunction, which may reduce the systemic inflammatory response.

Intestine; Ischemia-Reperfusion Injury; Gastrointestinal Motility; Estradiol; Inflammation


INTRODUCTION

Acute mesenteric ischemia is characterized by the interruption of blood flow to the intestine and is most commonly attributed to the obstruction of the superior mesenteric artery (SMA) (11. Assar AN, Zarins CK. Acute mesenteric ischaemia: facts and perspectives. Br J Hosp Med (Lond). 2008;69(12):686-91. https://doi.org/10.12968/hmed.2008.69.12.686
https://doi.org/10.12968/hmed.2008.69.12...
). This difficult-to-diagnose emergency can result in severe local and systemic inflammation and should be quickly treated; moreover, it presents a high morbidity and mortality rate (22. Oldenburg WA, Lau LL, Rodenberg TJ, Edmonds HJ, Burger CD. Acute mesenteric ischemia: a clinical review. Arch Intern Med. 2004;164(10):1054-62. https://doi.org/10.1001/archinte.164.10.1054
https://doi.org/10.1001/archinte.164.10....
,33. Leone M, Bechis C, Baumstarck K, Ouattara A, Collange O, Augustin P, et al. Outcome of acute mesenteric ischemia in the intensive care unit: a retrospective, multicenter study of 780 cases. Intensive Care Med. 2015;41(4):667-76. https://doi.org/10.1007/s00134-015-3690-8
https://doi.org/10.1007/s00134-015-3690-...
). Therefore, treatments that can promptly control the progress of inflammatory processes and subsequent tissue injury induced by ischemia and reperfusion (I/R) should be investigated.

Ischemia is characterized by a period of hypoxia, associated with a loss of cell barrier function and an increase in vascular permeability (44. Carden DL, Granger DN. Pathophysiology of ischaemia-reperfusion injury. J Pathol. 2000;190(3):255-66. https://doi.org/10.1002/(SICI)1096-9896(200002)190:3<255::AID-PATH526>3.0.CO;2-6
https://doi.org/10.1002/(SICI)1096-9896(...
). It can result in the disruption of the intestinal mucosal barrier, thus affecting both endothelial and epithelial barriers. During the reperfusion period, inflammation is further exacerbated via the introduction of oxygen, thus leading to the production of several oxygen reactive species while further attracting neutrophils (55. Mallick IH, Yang W, Winslet MC, Seifalian AM. Ischemia-reperfusion injury of the intestine and protective strategies against injury. Dig Dis Sci. 2004;49(9):1359-77. https://doi.org/10.1023/B:DDAS.0000042232.98927.91
https://doi.org/10.1023/B:DDAS.000004223...
). Along with tissue damage, intestinal I/R injury can result in abnormalities in intestinal motility (66. Pontell L, Sharma P, Rivera LR, Thacker M, Tan YH, Brock JA, et al. Damaging effects of ischemia/reperfusion on intestinal muscle. Cell Tissue Res. 2011;343(2):411-9. https://doi.org/10.1007/s00441-010-1096-z
https://doi.org/10.1007/s00441-010-1096-...
).

Studies have revealed that female sex hormones, specifically estradiol, can afford protective effects in the intestines not only in intestinal I/R injury models but also under conditions of trauma-hemorrhage shock. Furthermore, estradiol plays a role in controlling inflammatory markers during intestinal I/R injury (77. Kuebler JF, Jarrar D, Toth B, Bland KI, Rue L 3rd, Wang P, et al. Estradiol administration improves splanchnic perfusion following trauma-hemorrhage and sepsis. Arch Surg. 2002;137(1):74-9. https://doi.org/10.1001/archsurg.137.1.74
https://doi.org/10.1001/archsurg.137.1.7...

8. Chen J, Yang S, Hu S, Choudhry MA, Bland KI, Chaudry IH. Estrogen prevents intestinal inflammation after trauma-hemorrhage via downregulation of angiotensin II and angiotensin II subtype I receptor. Am J Physiol Gastrointest Liver Physiol. 2008;295(5):G1131-7. https://doi.org/10.1152/ajpgi.90443.2008
https://doi.org/10.1152/ajpgi.90443.2008...
-99. Ricardo-da-Silva FY, Fantozzi ET, Rodrigues-Garbin S, Oliveira-Filho RM, Vargaftig BB, Breithaupt-Faloppa AC, et al. Estradiol Modulates Local Gut Injury Induced by Intestinal Ischemia-Reperfusion in Male Rats. Shock. 2017;48(4):477-83. https://doi.org/10.1097/SHK.0000000000000873
https://doi.org/10.1097/SHK.000000000000...
). Indeed, we have previously identified that estradiol treatment attenuated intestinal I/R-induced gut injury in male rats, modulating local chemokine release and leukocyte mobilization (99. Ricardo-da-Silva FY, Fantozzi ET, Rodrigues-Garbin S, Oliveira-Filho RM, Vargaftig BB, Breithaupt-Faloppa AC, et al. Estradiol Modulates Local Gut Injury Induced by Intestinal Ischemia-Reperfusion in Male Rats. Shock. 2017;48(4):477-83. https://doi.org/10.1097/SHK.0000000000000873
https://doi.org/10.1097/SHK.000000000000...
). However, the mechanism underlying the modulatory role of estradiol with functional aspects of the gut after intestinal I/R injury remains unknown. Thus, the objective of the present study was to further investigate the effects of estradiol treatment on intestinal integrity and function after intestinal I/R injury.

MATERIALS AND METHODS

Animals

Adult male Wistar rats (60 days, n=24) were procured from our departmental animal facilities and housed five per cage in a temperature-controlled room (12-h light-dark cycle, 21±2°C), with free access to water and food. This study was approved by the Animal Care Committee of the Institute of Biomedical Sciences, University of Sao Paulo, following the guidelines of the National Council of Animal Experimentation, which regulates animal research according to the Brazilian Federal Law (Report no. 111/10/03).

Study groups

The animals were randomized into three groups: 1) sham, rats undergoing surgical procedures, with no I/R induction; 2) I/R, rats undergoing intestinal I/R injury; 3) E30, rats undergoing intestinal I/R injury and treated with 17β-estradiol (280 μg/kg, intravenously [i.v.]) 30 min after ischemia induction.

Intestinal I/R injury rat model

In brief, the rats were anesthetized with ketamine/xylazine (100 mg/kg and 20 mg/kg, respectively, intraperitoneally [i.p.]), and a midline laparotomy was performed to expose the abdominal cavity. Then, the superior mesenteric artery (SMA) was isolated and clamped for 45 min. Intestinal reperfusion was performed for 2h after vascular clamp retrieval (99. Ricardo-da-Silva FY, Fantozzi ET, Rodrigues-Garbin S, Oliveira-Filho RM, Vargaftig BB, Breithaupt-Faloppa AC, et al. Estradiol Modulates Local Gut Injury Induced by Intestinal Ischemia-Reperfusion in Male Rats. Shock. 2017;48(4):477-83. https://doi.org/10.1097/SHK.0000000000000873
https://doi.org/10.1097/SHK.000000000000...
). Sham-operated rats served as controls. All animals were euthanized with an anesthesia overdose and exsanguinated via the abdominal aorta. No animals were lost due to the I/R model.

Estradiol treatment and quantification of hormonal serum concentration

Thirty minutes after clamping the SMA (ischemia period), a single intravenous injection of 17β-estradiol (280 µg/kg; Sigma-Aldrich®, USA) dissolved in a sterile saline solution (0.9%) was administered. Serum estradiol levels were determined using an EIA kit (Cayman Chemical Company, USA) in samples (n=5) obtained at the end of the intestinal reperfusion period, according to the manufacturer’s specifications.

Gastrointestinal transit evaluation

Based on the gastrointestinal transit method described by Manara et al. (1010. Manara L, Bianchi G, Ferretti P, Tavani A. Inhibition of gastrointestinal transit by morphine in rats results primarily from direct drug action on gut opioid sites. J Pharmacol Exp Ther. 1986;237(3):945-9.), overnight-fasted rats were fed 1 mL of 20% activated charcoal in phosphate-buffered saline (PBS) by oral gavage (Lafan Química Fina Ltda, Brazil). After the I/R injury period, the small intestine was retrieved to measure the total length (from the pyloric sphincter to the ileocecal junction) and the distance traveled by the activated charcoal was assessed (from the pyloric sphincter to the furthest point where 1 cm of continuous activated charcoal moved). Data were recorded as a percentage of the total length (percentage of gastrointestinal transit).

Intestinal mucosal permeability assay

After initiating the reperfusion period under anesthesia, rats were administered intraduodenal dextran-FITC (50 mg/kg, 4 kD, Sigma-Aldrich®, USA) diluted in PBS (1111. Costantini TW, Loomis WH, Putnam JG, Drusinsky D, Deree J, Choi S, et al. Burn-induced gut barrier injury is attenuated by phosphodiesterase inhibition: effects on tight junction structural proteins. Shock. 2009;31(4):416-22. https://doi.org/10.1097/SHK.0b013e3181863080
https://doi.org/10.1097/SHK.0b013e318186...
). Following intestinal reperfusion for 2h, blood samples were collected from the abdominal aorta, and serum aliquots were processed and stored in a freezer (-80°C). Dextran-FITC fluorescence was determined spectrophotometrically (495 nm Synergy HTX, BioTek®, USA), and values were plotted in a standard curve (2,000-0.24 ng/mL), expressed in ng/mL.

Expression of endothelin and endothelial nitric oxide synthase in mesenteric vessels

In brief, mesentery samples, frozen immediately after retrieval, were sectioned (8 μm) (Leica CM1850 Cryostat; Leica Biosystems, USA) and fixed in cold acetone (10 min). Endogenous peroxidase blockade was performed, and sections were incubated for 15 min in H2O2 (2%), followed by non-specific blocking with Tris-Buffered Saline-Tween20 (TBST) containing bovine serum albumin (1%) for 15 min. Next, the sections were incubated for 1 h at 37°C with primary antibodies, either endothelial nitric oxide synthase (eNOS) or endothelin-1(ET-1) (1:100; Abcam, UK). After rinsing with TBST, sections were incubated for 2h at 37°C with horseradish peroxidase (HRP)-conjugated secondary antibodies (1:200; Millipore, USA). HRP-substrate (AEC, Vector Laboratories, USA) was used for staining and hematoxylin for counterstaining. AEC-stained structures were identified using an image analyzer (NIS-elements®, Nikon, Japan) and expressed as stained area/total area. Sections incubated in the absence of the primary antibody were used as negative controls for the reaction.

Serum concentration of inflammatory and tissue injury biomarkers

Serum levels of vascular endothelial growth factor (VEGF), interferon-gamma inducible-protein-10 (IP-10), tumor necrosis factor (TNF)-α, interleukin (IL)-10, IL-1β, and IL-6 were quantified. Analyses were performed using a Milliplex® MAP kit (EMD Millipore Corporation, USA) and expressed as pg/mL. Quantification was performed using the Luminex 200-Software xPonent/Analyst 4.2 version (EMD Millipore Corporation, USA). Lactate dehydrogenase (LDH) and alkaline phosphatase activity were measured as indirect indicators of intestinal I/R injury using commercial kits according to the manufacturer's instructions (Quibasa Química Básica Ltda., Brazil).

Statistical analysis

All data are presented as the mean±standard error of the mean (SEM) and were analyzed by ANOVA, followed by Tukey-Kramer multiple comparison test or Bonferroni post hoc test. Data analyses were performed using GraphPad Prism version 8.3.1 (GraphPad Software, Inc., La Jolla, CA, USA). Statistical significance was set at p<0.05 and is described in the figure legends, whereas the ANOVA p-values are shown in the figures.

RESULTS

Serum estradiol concentration in male rats

First, we quantified the serum estradiol levels in the study groups. Intestinal I/R injury did not alter the estradiol serum levels, but estradiol-treated rats presented high serum estradiol concentrations (Sham: 55.7±25.17 pg/mL; I/R: 94.81±14.46; E30:17,904±3,652*; *p<0.0001 compared with I/R).

Effect of estradiol treatment on intestinal transit

As shown in Figure 1, intestinal I/R injury significantly reduced gastrointestinal transit when compared with that in animals from the sham group. Estradiol treatment effectively prevented transit reduction, with values similar to those in sham animals.

Figure 1
Effect of intestinal I/R injury on the gastrointestinal transit (%). In rats with I/R injury, the superior mesenteric artery was clamped (45 min), followed by intestinal reperfusion (2h). Estradiol (180 µg/kg, i.v.) was administered 30 min after the induction of intestinal ischemia (E30). Sham-operated rats were used as controls. Data are expressed as the mean±standard error of the mean (SEM) from 6 animals. *p=0.011 compared with the sham group; γp=0.0457 versus intestinal I/R group. I/R, ischemia and reperfusion.

Role of estradiol in intestinal mucosa permeability

As shown in Figure 2, intestinal I/R injury enhanced the permeability of the intestinal mucosa, as observed by the elevated concentration of dextran-FITC in the serum, compared with the sham group. Conversely, estradiol treatment significantly reduced the concentration of serum dextran-FITC compared with that in the I/R group.

Figure 2
The effect of reperfusion in intestinal I/R on intestinal mucosal permeability. In rats with I/R injury, the superior mesenteric artery was clamped (45 min), followed by intestinal reperfusion (2h). Estradiol (180 µg/kg, i.v.) was administered 30 min after the induction of intestinal ischemia (E30). Sham-operated rats were used as controls. Data are expressed as the mean±standard error of the mean (SEM) from 6 animals. *p<0.0001 compared with sham; γp=0.0036 versus intestinal I/R. I/R, ischemia and reperfusion.

Estradiol treatment and eNOS and ET-1 expression in mesenteric vessels

Figure 3 and Figure 4 present the eNOS and ET-1 protein expression levels, respectively, in the mesenteric vessels. Intestinal I/R injury reduced the expression of both eNOS and ET-1, and estradiol treatment (group E30) increased the protein expression levels of both eNOS and ET-1.

Figure 3
Quantification of eNOS (panel A) and endothelin-1 (panel B) expression in mesenteric vessels. In rats with I/R injury, the superior mesenteric artery was clamped (45 min), followed by intestinal reperfusion (2h). Estradiol (180 µg/kg, i.v.) was administered 30 min after induction of intestinal ischemia (E30). Sham-operated rats were used as control. Data are expressed as the mean±standard error of the mean (SEM) from 4 animals/group (2 tissue sections/animal). Panel A: *p=0.0026 compared with the sham group; γp<0.0001 compared to intestinal I/R. Panel B: *p<0.0001 versus sham group; γp<0.0001 versus intestinal I/R. eNOS, endothelial nitric oxide synthase; I/R, ischemia and reperfusion.
Figure 4
Immunohistochemistry analysis of the expression of endothelial nitric oxide synthase (eNOS) and endothelin (ET-1) in mesenteric vessels. Original magnification, ×40 for all images. In rats with I/R injury, the superior mesenteric artery was clamped (45 min), followed by intestinal reperfusion (2h). Estradiol (180 µg/kg, i.v.) was administered 30 min after the induction of intestinal ischemia (E30). Sham-operated rats were used as controls. I/R, ischemia and reperfusion.

Estradiol treatment and serum levels of injury markers

Figure 5A shows an increase in the serum LDH levels following intestinal I/R injury compared with the case in the sham group. Estradiol treatment effectively prevented an increase in the LDH levels. Although intestinal I/R injury did not alter the serum levels of alkaline phosphatase, estradiol treatment reduced its concentration (Figure 5B).

Figure 5
Serum concentrations of lactate dehydrogenase (Panel A) and alkaline phosphatase activity. (Panel B). A group of rats had their superior mesenteric arteries clamped (45 min), followed by intestinal reperfusion (2h). Estradiol (180 µg/kg, i.v.) was administered 30 min after induction of intestinal ischemia (E30). Sham-operated rats were used as control. Data are expressed as the mean±standard error of the mean (SEM) from 8 animals. Panel A: *p=0.0081 compared with sham; γp=0.0066 compared with I/R. Panel B: γp=0.0088 compared with I/R. I/R, ischemia and reperfusion.

Estradiol-mediated control of the release of inflammatory mediators

As shown in Figure 6 (panels A-F), the induction of intestinal I/R injury increased the serum concentrations of VEGF, IP-10, TNF-α, IL-10, IL-1β, and IL-6. Conversely, estradiol treatment prevented the increase in the expression levels of VEGF, IP-10, IL-10, and IL-1β.

Figure 6
Effects of intestinal I/R injury and estradiol treatment on the serum levels of VEGF (panel A), IP-10 (panel B), TNFα (panel C), IL-10 (panel D), IL-1β (panel D), and IL-6 (panel E). In I/R injury rats, the superior mesenteric artery was clamped (45 min), followed by intestinal reperfusion (2h). Estradiol (180 µg/kg, i.v.) was administered 30 min after induction of intestinal ischemia (E30). Sham-operated rats were used as controls. Data are expressed as the mean±standard error of the mean (SEM) from 8 animals. *p≤0.05 compared with sham; γp≤0.05 compared with I/R. I/R, ischemia and reperfusion; VEGF, vascular endothelial growth factor; IP-10, inducible-protein-10 IL-10, interleukin 10; IL-1β, interleukin-1β; TNFα, tumor necrosis factor-alpha.

DISCUSSION

Intestinal I/R accounts for the induction of local, systemic, and remote organ injuries. Toxic products and inflammatory mediators released locally during the ischemic period could reach the systemic compartment during reperfusion, thus impacting the functions of remote organs and becoming life-threatening (1212. Mura M, Andrade CF, Han B, Seth R, Zhang Y, Bai XH, et al. Intestinal ischemia-reperfusion-induced acute lung injury and oncotic cell death in multiple organs. Shock. 2007;28(2):227-38. https://doi.org/10.1097/SHK.0b013e318033e927
https://doi.org/10.1097/SHK.0b013e318033...
,1313. Lawson RM. Mesenteric Ischemia. Crit Care Nurs Clin North Am. 2018;30(1):29-39. https://doi.org/10.1016/j.cnc.2017.10.003
https://doi.org/10.1016/j.cnc.2017.10.00...
). This severe condition appears to be triggered by the intestinal I/R injury, which affects the functionality of intestinal tight junctions (1414. Kalogeris T, Baines CP, Krenz M, Korthuis RJ. Ischemia/Reperfusion. Compr Physiol. 2016;7(1):113-70. https://doi.org/10.1002/cphy.c160006
https://doi.org/10.1002/cphy.c160006...
). The intestinal mucosa acts as a barrier to control the passage of products from the intestine into the systemic compartment (1515. Turner JR. Intestinal mucosal barrier function in health and disease. Nat Rev Immunol. 2009;9(11):799-809. https://doi.org/10.1038/nri2653
https://doi.org/10.1038/nri2653...
). Moreover, excessive activation of mucosal permeability by substances translocated from the intestinal lumen has been associated with the induction of gut disease (1616. Odenwald MA, Turner JR. Intestinal permeability defects: is it time to treat? Clin Gastroenterol Hepatol. 2013;11(9):1075-83. https://doi.org/10.1016/j.cgh.2013.07.001
https://doi.org/10.1016/j.cgh.2013.07.00...
).

In the present study, the experimental design addressed the hypothesis that estradiol locally modulates the inflammatory response induced by intestinal I/R injury, and consequently, systemic mediators/markers. Accordingly, we evaluated specific parameters associated with local and systemic inflammatory responses elicited by intestinal I/R injury in male rats. We revealed that tissue injury biomarkers, notably, intestinal permeability and serum levels of LDH, were increased after intestinal I/R injury. Previous studies have reported a loss of intestinal barrier integrity induced by gut ischemic events (1717. Feinman R, Deitch EA, Watkins AC, Abungu B, Colorado I, Kannan KB, et al. HIF-1 mediates pathogenic inflammatory responses to intestinal ischemia-reperfusion injury. Am J Physiol Gastrointest Liver Physiol. 2010;299(4):G833-43. https://doi.org/10.1152/ajpgi.00065.2010
https://doi.org/10.1152/ajpgi.00065.2010...
,1818. Ito H, Sadatomo A, Inoue Y, Yamada N, Aizawa E, Hishida E, et al. Role of TLR5 in inflammation and tissue damage after intestinal ischemia-reperfusion injury. Biochem Biophys Res Commun. 2019;519(1):15-22. https://doi.org/10.1016/j.bbrc.2019.08.083
https://doi.org/10.1016/j.bbrc.2019.08.0...
), with increased LDH levels detected in the serum after intestinal ischemia (1919. Cámara-Lemarroy CR, Guzmán-de la Garza FJ, Alarcón-Galván G, Cordero-Pérez P, Fernández-Garza NE. The effects of NMDA receptor antagonists over intestinal ischemia/reperfusion injury in rats. Eur J Pharmacol. 2009;621(1-3):78-85.). In a previous study, we observed that intestinal I/R injury reduces intestinal villous height (99. Ricardo-da-Silva FY, Fantozzi ET, Rodrigues-Garbin S, Oliveira-Filho RM, Vargaftig BB, Breithaupt-Faloppa AC, et al. Estradiol Modulates Local Gut Injury Induced by Intestinal Ischemia-Reperfusion in Male Rats. Shock. 2017;48(4):477-83. https://doi.org/10.1097/SHK.0000000000000873
https://doi.org/10.1097/SHK.000000000000...
). Therefore, we aimed to investigate the functional aspects of the intestine after I/R injury. Herein, we observed that the intestinal transit distance was reduced in experimental animals. Interestingly, Woting and Blaut (2020. Woting A, Blaut M. Small Intestinal Permeability and Gut-Transit Time Determined with Low and High Molecular Weight Fluorescein Isothiocyanate-Dextrans in C3H Mice. Nutrients. 2018;10(6):685. https://doi.org/10.3390/nu10060685
https://doi.org/10.3390/nu10060685...
) have indicated that changes in the intestinal permeability could influence the intestinal transit time. As increased mucosal permeability could account for tissue injury, based on our findings, we speculated whether the reduced intestinal transit could promote a long-lasting interaction between toxic products/inflammatory mediators generated by intestinal I/R injury and intestinal mucosal surfaces, thus contributing to the severity of local inflammation and systemic repercussions. Therefore, estradiol affords protective effects against intestinal transit and could potentially contribute to diminishing this deleterious interaction.

Narita et al. (2121. Narita K, Kuwabara Y, Fujii Y. Lung injury after intestinal ischemia-reperfusion may be avoided by the reduced absorption of locally produced cytokines. Surg Today. 2004;34(11):937-42. https://doi.org/10.1007/s00595-004-2847-9
https://doi.org/10.1007/s00595-004-2847-...
) have reported a correlation between the elevated cytokine concentration in the peritoneum after intestinal I/R injury, along with the development of lung inflammation. These authors reinforced the concept of the local influence of intestinal I/R to induce lung inflammation. Using the methodology described by Narita et al. (2121. Narita K, Kuwabara Y, Fujii Y. Lung injury after intestinal ischemia-reperfusion may be avoided by the reduced absorption of locally produced cytokines. Surg Today. 2004;34(11):937-42. https://doi.org/10.1007/s00595-004-2847-9
https://doi.org/10.1007/s00595-004-2847-...
), we detected elevated levels of TNF-α and IL-10 in peritoneal fluid collected after induction of intestinal I/R (99. Ricardo-da-Silva FY, Fantozzi ET, Rodrigues-Garbin S, Oliveira-Filho RM, Vargaftig BB, Breithaupt-Faloppa AC, et al. Estradiol Modulates Local Gut Injury Induced by Intestinal Ischemia-Reperfusion in Male Rats. Shock. 2017;48(4):477-83. https://doi.org/10.1097/SHK.0000000000000873
https://doi.org/10.1097/SHK.000000000000...
), which could explain the gut injury caused by intestinal I/R. Notably, disruption of the gut barrier during intestinal ischemia is associated with the induction of intestinal inflammation, generation of pro-inflammatory mediators, and remote organ failure (2222. Deitch EA. Gut-origin sepsis: evolution of a concept. Surgeon. 2012;10(6):350-6. https://doi.org/10.1016/j.surge.2012.03.003
https://doi.org/10.1016/j.surge.2012.03....
).

Moreover, it is essential to note that blood supply to the mesenteric compartment is finely tuned by local mechanisms (22. Oldenburg WA, Lau LL, Rodenberg TJ, Edmonds HJ, Burger CD. Acute mesenteric ischemia: a clinical review. Arch Intern Med. 2004;164(10):1054-62. https://doi.org/10.1001/archinte.164.10.1054
https://doi.org/10.1001/archinte.164.10....
), and the lack of normal endothelial cell function accounts for the lesion observed after intestinal I/R (44. Carden DL, Granger DN. Pathophysiology of ischaemia-reperfusion injury. J Pathol. 2000;190(3):255-66. https://doi.org/10.1002/(SICI)1096-9896(200002)190:3<255::AID-PATH526>3.0.CO;2-6
https://doi.org/10.1002/(SICI)1096-9896(...
). Thus, we evaluated the functional activity of mesenteric vessels in terms of ET-1 and eNOS expression. Khanna et al. (2323. Khanna A, Rossman JE, Fung HL, Caty MG. Attenuated nitric oxide synthase activity and protein expression accompany intestinal ischemia/reperfusion injury in rats. Biochem Biophys Res Commun. 2000;269(1):160-4. https://doi.org/10.1006/bbrc.2000.2266
https://doi.org/10.1006/bbrc.2000.2266...
) have reported decreased intestinal eNOS activity during intestinal reperfusion. This decrease in NO release can be associated with peroxynitrite production and gut permeability injury (2424. Ward DT, Lawson SA, Gallagher CM, Conner WC, Shea-Donohue T. Sustained nitric oxide production via l-arginine administration ameliorates effects of intestinal ischemia-reperfusion. J Surg Res. 2000;89(1):13-9. https://doi.org/10.1006/jsre.1999.5795
https://doi.org/10.1006/jsre.1999.5795...
). In the present study, we detected decreased eNOS expression in the mesenteric vessels, suggesting that intestinal homeostasis was disrupted by mesenteric artery occlusion. Consistently, data from the literature have revealed that intestinal I/R injury increased the plasma levels of ET and modified the mesenteric expression of ET receptors A and B (2525. Martínez-Revelles S, Caracuel L, Márquez-Martín A, Dantas A, Oliver E, D'Ocon P, et al. Increased endothelin-1 vasoconstriction in mesenteric resistance arteries after superior mesenteric ischaemia-reperfusion. Br J Pharmacol. 2012;165(4):937-50. https://doi.org/10.1111/j.1476-5381.2011.01617.x
https://doi.org/10.1111/j.1476-5381.2011...
). Furthermore, Oktar et al. (2626. Oktar BK, Coşkun T, Bozkurt A, Yegen BC, Yüksel M, Haklar G, et al. Endothelin-1-induced PMN infiltration and mucosal dysfunction in the rat small intestine. Am J Physiol Gastrointest Liver Physiol. 2000;279(3):G483-91. https://doi.org/10.1152/ajpgi.2000.279.3.G483
https://doi.org/10.1152/ajpgi.2000.279.3...
) have shown an increase in intestinal mucosal permeability, neutrophil influx, and free radicals release in the rat mesentery compartment following ET-1 infusion. Our data demonstrated reduced ET expression in mesenteric vessels after intestinal I/R injury. Endothelial cells produce and release ET-1, which, when bound to ET-A receptors, leads to vasoconstriction. Conversely, ET-B receptors located on endothelial cells bind to nitric oxide or increase prostacyclin formation, resulting in vasodilation (2727. Pollock JS, Pollock DM. Endothelin and NOS1/nitric oxide signaling and regulation of sodium homeostasis. Curr Opin Nephrol Hypertens. 2008;17(1):70-5. https://doi.org/10.1097/MNH.0b013e3282f34b02
https://doi.org/10.1097/MNH.0b013e3282f3...
). Moreover, ET has been implicated in the physiological modulation of intestinal motility and secretion (2828. Egidy G, Juillerat-Jeanneret L, Korth P, Bosman FT, Pinet F. The endothelin system in normal human colon. Am J Physiol Gastrointest Liver Physiol. 2000;279(1):G211-22. https://doi.org/10.1152/ajpgi.2000.279.1.G211
https://doi.org/10.1152/ajpgi.2000.279.1...
). Considering these data and the augmented serum concentrations of VEGF, IP-10, IL-1β, and IL-10 after intestinal I/R injury, local control of injury represents an important target to mitigate the remote organ dysfunction observed following intestinal ischemic events.

Several lines of evidence indicate that female sex hormones, notably estradiol, exert an anti-inflammatory role. Indeed, Song et al. (2929. Song CH, Kim N, Sohn SH, Lee SM, Nam RH, Na HY, et al. Effects of 17β-Estradiol on Colonic Permeability and Inflammation in an Azoxymethane/Dextran Sulfate Sodium-Induced Colitis Mouse Model. Gut Liver. 2018;12(6):682-93. https://doi.org/10.5009/gnl18221
https://doi.org/10.5009/gnl18221...
) have demonstrated that estradiol effectively reduces intestinal injury caused by experimental colitis, decreasing intestinal permeability, nuclear factor kappa B (NF-κB) expression, and increasing mucus generation. Rocha de Sousa et al. (3030. Rocha de Sousa PT, Breithaupt-Faloppa AC, de Jesus Correia C, Simão RR, Ferreira SG, Fiorelli AI, et al. 17β-Estradiol prevents mesenteric injury induced by occlusion of the proximal descending aorta in male rats. J Vasc Surg. 2018;67(2):597-606. https://doi.org/10.1016/j.jvs.2016.12.125
https://doi.org/10.1016/j.jvs.2016.12.12...
) have investigated mesenteric injury induced by the obstruction of the aorta in rats. Their findings revealed the preventive action of estradiol whereby it increased the mesenteric eNOS expression, while decreasing the degree of inflammation and mortality. By ameliorating intestinal perfusion, estradiol reportedly improves systemic, cardiac, and intestinal villous injuries observed in an experimental model of trauma-hemorrhage and sepsis (77. Kuebler JF, Jarrar D, Toth B, Bland KI, Rue L 3rd, Wang P, et al. Estradiol administration improves splanchnic perfusion following trauma-hemorrhage and sepsis. Arch Surg. 2002;137(1):74-9. https://doi.org/10.1001/archsurg.137.1.74
https://doi.org/10.1001/archsurg.137.1.7...
,3131. Doucet D, Badami C, Palange D, Bonitz RP, Lu Q, Xu DZ, et al. Estrogen receptor hormone agonists limit trauma hemorrhage shock-induced gut and lung injury in rats. PLoS One. 2010;5(2):e9421. https://doi.org/10.1371/journal.pone.0009421
https://doi.org/10.1371/journal.pone.000...
). Moreover, we have previously shown that estradiol protects the intestinal villus against intestinal I/R injury in male rats (99. Ricardo-da-Silva FY, Fantozzi ET, Rodrigues-Garbin S, Oliveira-Filho RM, Vargaftig BB, Breithaupt-Faloppa AC, et al. Estradiol Modulates Local Gut Injury Induced by Intestinal Ischemia-Reperfusion in Male Rats. Shock. 2017;48(4):477-83. https://doi.org/10.1097/SHK.0000000000000873
https://doi.org/10.1097/SHK.000000000000...
).

Furthermore, estradiol is known to attenuate lung inflammation induced by intestinal ischemia (3131. Doucet D, Badami C, Palange D, Bonitz RP, Lu Q, Xu DZ, et al. Estrogen receptor hormone agonists limit trauma hemorrhage shock-induced gut and lung injury in rats. PLoS One. 2010;5(2):e9421. https://doi.org/10.1371/journal.pone.0009421
https://doi.org/10.1371/journal.pone.000...

32. Breithaupt-Faloppa AC, Fantozzi ET, de Assis Ramos MM, Vitoretti LB, Couto GK, Lino-dos-Santos-Franco A, et al. Protective effect of estradiol on acute lung inflammation induced by an intestinal ischemic insult is dependent on nitric oxide. Shock. 2013;40(3):203-9. https://doi.org/10.1097/SHK.0b013e3182a01e24
https://doi.org/10.1097/SHK.0b013e3182a0...

33. Breithaupt-Faloppa AC, Thais Fantozzi E, Romero DC, Rodrigues Ada S, de Sousa PT, Lino Dos Santos Franco A, et al. Acute effects of estradiol on lung inflammation due to intestinal ischemic insult in male rats. Shock. 2014;41(3):208-13. https://doi.org/10.1097/SHK.0000000000000092
https://doi.org/10.1097/SHK.000000000000...
-3434. Fantozzi ET, Breithaupt-Faloppa AC, Ricardo-da-Silva FY, Rodrigues-Garbin S, Romero DC, da Silva Rodrigues A, et al. Estradiol mediates the long-lasting lung inflammation induced by intestinal ischemia and reperfusion. J Surg Res. 2018;221:1-7. https://doi.org/10.1016/j.jss.2017.07.038
https://doi.org/10.1016/j.jss.2017.07.03...
), and based on our findings, this action could be a consequence of its intestinal effects. As highlighted by Deitch (3535. Deitch EA. Gut lymph and lymphatics: a source of factors leading to organ injury and dysfunction. Ann N Y Acad Sci. 2010;1207 Suppl 1:E103-11. https://doi.org/10.1111/j.1749-6632.2010.05713.x
https://doi.org/10.1111/j.1749-6632.2010...
), the intestine is the primary target of ischemic events to induce remote organ dysfunction.

In the present study, the protective effects of estradiol treatment were observed even after 30 min of intestinal ischemia and 15 min before intestinal perfusion was re-established. We revealed that estradiol exerted a protective role on the magnitude of the endpoints in relation to intestinal injury, such as LDH and mucosal permeability. Furthermore, estradiol effectively reduced the serum levels of VEGF, IP-10, and IL-1β, indicating a relationship between the protective effects of estradiol on the intestine and the attenuation of the inflammatory responses of remote organs, such as those observed during ischemic events. Furthermore, estradiol restored intestinal transit, possibly improving the functional activity of the intestine and recovering the capacity of mesenteric vessels to express eNOS and endothelin.

From a comprehensive perspective, we inferred that estradiol, by mediating the reestablishment of gut barrier functions and preventing local dysfunction, may reduce the systemic inflammatory response. Therefore, given that remote organ inflammation is a repercussion of local (intestinal) events induced by intestinal I/R injury, our findings hypothesize that the attenuation of remote organ dysfunction may be modulated by the protective effects of estradiol on intestinal lesions.

ACKNOWLEDGMENTS

Disclosure and consent for publication: The authors declare no conflicts of interest or consent for publication. This study was supported by the Fundação de Amparo è Pesquisa do Estado de São Paulo (Grant no. 2013/15291-0). Wothan Tavares-de-Lima is a fellow researcher at CNPq. Fernanda Yamamoto Ricardo da Silva was supported by CAPES. This study was financed, in part, by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001.

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Publication Dates

  • Publication in this collection
    26 Apr 2021
  • Date of issue
    2021

History

  • Received
    11 Dec 2020
  • Accepted
    4 Mar 2021
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