Ischemic post-conditioning to counteract intestinal ischemia/reperfusion injury

Shaping of Hepatic Ischemia/Reperfusion Events: The Crucial Role of Mitochondria

Hepatic ischemia reperfusion injury (HIRI) is a major hurdle in many clinical scenarios, including liver resection and transplantation. Various studies and countless surgical events have led to the observation of a strong correlation between HIRI induced by liver transplantation and early allograft-dysfunction development. The detrimental impact of HIRI has driven the pursuit of new ways to alleviate its adverse effects. At the core of HIRI lies mitochondrial dysfunction. Various studies, from both animal models and in clinical settings, have clearly shown that mitochondrial function is severely hampered by HIRI and that its preservation or restoration is a key indicator of successful organ recovery. Several strategies have been thus implemented throughout the years, targeting mitochondrial function. This work briefly discusses some the most utilized approaches, ranging from surgical practices to pharmacological interventions and highlights how novel strategies can be investigated and implemented by intricately discussing the way mitochondrial function is affected by HIRI.

Protective Effect of Zinc Supplementation on Renal Ischemia/Reperfusion Injury in Rat: Gender-related Difference

Background:

Zinc (Zn) knows as essential microelement which prevents oxidative stress. The effect of Zn supplement on renal function parameters in rats subjected to renal ischemia-reperfusion (IR) injury was investigated.

Methods:

Male and female rats were subjected to renal IR with and without Zn sulfate (10 mg/kg/day for 5 days) supplementation. The kidney function markers and histology findings in Zn-treated group were compared with sham and control groups.

Results:

The serum levels of blood urea nitrogen and creatinine (Cr) and kidney tissue damage score were increased significantly after renal injury (P < 0.05) gender dependently, but no alterations were observed for these markers in Zn-treated animals after renal IR injury. Cr clearance was significantly different between genders (P < 0.05); however, Zn supplementation increased the Cr clearance and kidney nitrite level significantly in male rats (P < 0.05). Zn also increased urine flow in female (P < 0.05), but it did not alter urine load of Na (U_NaV) and percentage of Na excretion (E_Na%).

Conclusions:

Zn may improve renal function after IR injury gender dependently.

Aryl hydrocarbon receptor activation modulates γδ intestinal intraepithelial lymphocytes and protects against ischemia/reperfusion injury in the murine small intestine

The pathogenesis of intestinal ischemia/reperfusion (I/R) is associated with dysregulation of the intestinal immune system. The aryl hydrocarbon receptor (AhR), a receptor expressed in gamma‑delta (γδ) intraepithelial lymphocytes (IELs), is thought to regulate inflammation in the bowel. γδIELs are a key immunologic compartment with a capacity to modulate immune responses. In the present study, the function of the AhR in γδIELs in a mouse model of intestinal I/R injury was investigated to determine whether the AhR attenuates intestinal injury induced by intestinal I/R. Mice were assigned to three groups: sham, I/R and I/R+6‑formylindolo(3,2‑b)carbazole (FICZ). The sham group received no ischemia treatment, whereas the I/R and I/R+FICZ groups underwent upper mesenteric vessel ischemia for 30 min. The I/R group was injected intraperitoneally with 0.3 ml saline and the I/R+FICZ group was administered 1 µg of FICZ before a subsequent 6 h reperfusion. Then, the mice were sacrificed and the entire small intestinal tissues were collected for histologic examination. The phenotype and apoptosis of γδIELs and activation of CD4+ and CD8+ IELs were examined using flow cytometry. The cytokine mRNA and anti‑apoptosis gene expression in IELs were measured by qPCR. FICZ increased the γδIEL population and anti‑apoptosis genes in the γδIELs. FICZ reduced the percentage of activated CD4+ and CD8+ subpopulations and the expression of pro‑inflammatory mediator genes in IELs. FICZ inhibited inflammation in the gastrointestinal tract of mice with I/R injury. These results suggest that the AhR plays an important role in protecting the small intestine from I/R and increasing the γδIEL population by decreasing apoptosis of γδIELs.

Hepatic ischemia reperfusion injury: A systematic review of literature and the role of current drugs and biomarkers

Hepatic ischemia reperfusion injury (IRI) is not only a pathophysiological process involving the liver, but also a complex systemic process affecting multiple tissues and organs. Hepatic IRI can seriously impair liver function, even producing irreversible damage, which causes a cascade of multiple organ dysfunction. Many factors, including anaerobic metabolism, mitochondrial damage, oxidative stress and secretion of ROS, intracellular Ca(2+) overload, cytokines and chemokines produced by KCs and neutrophils, and NO, are involved in the regulation of hepatic IRI processes. Matrix Metalloproteinases (MMPs) can be an important mediator of early leukocyte recruitment and target in acute and chronic liver injury associated to ischemia. MMPs and neutrophil gelatinase-associated lipocalin (NGAL) could be used as markers of I-R injury severity stages. This review explores the relationship between factors and inflammatory pathways that characterize hepatic IRI, MMPs and current pharmacological approaches to this disease.

Mechanisms of hepatic ischemia-reperfusion injury and protective effects of nitric oxide

Hepatic ischemia-reperfusion injury (IRI) is a pathophysiological event post liver surgery or transplantation and significantly influences the prognosis of liver function. The mechanisms of IRI remain unclear, and effective methods are lacking for the prevention and therapy of IRI. Several factors/pathways have been implicated in the hepatic IRI process, including anaerobic metabolism, mitochondria, oxidative stress, intracellular calcium overload, liver Kupffer cells and neutrophils, and cytokines and chemokines. The role of nitric oxide (NO) in protecting against liver IRI has recently been reported. NO has been found to attenuate liver IRI through various mechanisms including reducing hepatocellular apoptosis, decreasing oxidative stress and leukocyte adhesion, increasing microcirculatory flow, and enhancing mitochondrial function. The purpose of this review is to provide insights into the mechanisms of liver IRI, indicating the potential protective factors/pathways that may help to improve therapeutic regimens for controlling hepatic IRI during liver surgery, and the potential therapeutic role of NO in liver IRI.

Impaired intestinal mucosal barrier upon ischemia-reperfusion: "patching holes in the shield with a simple surgical method"

Mesenteric ischemia-reperfusion (IR) is associated with impairment of the gut barrier function and the initiation of a proinflammatory cascade with life-threatening results. Therefore methods directed to ameliorate IR injury are of great importance. We aimed at describing the effects of postconditioning (PC) on the alterations of the intestinal mucosal function and the inflammatory response upon mesenteric IR. Methods. Male Wistar rats were gavaged with green fluorescent protein-expressing E. coli suspensions. Animals were randomized into three groups (n = 15), sham-operated, IR-, and PC-groups, and underwent 60 minutes of superior mesenteric artery occlusion, followed by 6 hours of reperfusion. Postconditioning was performed at the onset of reperfusion. Blood and tissue samples were taken at the end of reperfusion, for histological, bacteriological, and plasma examinations. Results. The PC-group presented a more favorable claudin-2, claudin-3, claudin-4, and zonula occludens-1 membrane expression profile, and significantly lower rates of bacterial translocation to distant organs and plasma D-lactate levels compared to the IR-group. Histopathological lesions, plasma I-FABP, IL-6, and TNF-α levels were significantly lower in the PC-group compared to the IR-group. Conclusion. The use of postconditioning improved the integrity of the intestinal mucosal barrier upon mesenteric IR, and thus reduced the incidence of bacterial translocation and development of a systemic inflammatory response.

Regional susceptibility to stress-induced intestinal injury in the mouse

Injury to the intestinal mucosa is a life-threatening problem in a variety of clinical disorders, including hemorrhagic shock, trauma, burn, pancreatitis, and heat stroke. The susceptibility to injury of different regions of intestine in these disorders is not well understood. We compared histological injury across the small intestine in two in vivo mouse models of injury, hemorrhagic shock (30% loss of blood volume) and heat stroke (peak core temperature 42.4°C). In both injury models, areas near the duodenum showed significantly greater mucosal injury and reductions in villus height. To determine if these effects were dependent on circulating factors, experiments were performed on isolated intestinal segments to test for permeability to 4-kDa FITC-dextran. The segments were exposed to hyperthermia (42°C for 90 min), moderate simulated ischemia (Po2 ∼30 Torr, Pco2 ∼60 Torr, pH 7.1), severe ischemia (Po2 ∼20 Torr, Pco2 ∼80 Torr, pH 6.9), or severe hypoxia (Po2 ∼0 Torr, Pco2 ∼35 Torr) for 90 min, and each group was compared with sham controls. All treatments resulted in marked elevations in permeability within segments near the duodenum. In severe hypoxia or hyperthermia, permeability was also moderately elevated in the jejunum and ileum; in moderate or severe ischemia, permeability was unaffected in these regions. The results demonstrate increased susceptibility of proximal regions of the small intestine to acute stress-induced damage, irrespective of circulating factors. The predominant injury in the duodenum may impact the pattern of acute inflammatory responses arising from breach of the intestinal barrier, and such knowledge may be useful for designing therapeutic strategies.

Heparin-binding epidermal growth factor-like growth factor protects rat intestine after portal triad clamping

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a potent mitogen and chemotactic factor. HB-EGF attenuates intestinal ischemia/reperfusion injury caused by superior mesenteric artery occlusion. We examined whether HB-EGF offers protection against intestinal congestion/reperfusion (C/R) injury, which is caused by portal triad clamping. Male Sprague-Dawley rats were randomly divided into three equally sized groups: I, sham-operated; II, portal triad clamping (Pringle maneuver); III, II + intraluminal administration of HB-EGF. Compared with sham-operated rats, all rats in group II exhibited significant increases in intestinal histologic injury, pro-inflammatory cytokine expression, myeloperoxidase activity, malonaldehyde levels, and apoptosis indices. Intraluminal administration of HB-EGF in group III significantly reduced these indicators when compared with group II. Clamping of the portal triad followed by reperfusion causes intestinal C/R injury and intraluminal administration of HB-EGF reduces the severity of intestinal C/R injury in rats.