Remote effect of kidney ischemia-reperfusion injury on pancreas: role of oxidative stress and mitochondrial apoptosis

Abstract

Introduction: Recent studies have demonstrated remote effects of renal ischemia/reperfusion (IR) injury on some organs such as brain, liver, and lungs. Oxidative stress is reported to be the cornerstone in such ischemic conditions. Associated apoptosis is also reported in remote lung, liver and myocardial injury after acute kidney injury. So, we postulated that renal IR may affect the pancreas by its remote effect. Oxidative stress and mitochondrial mediated apoptosis may play a crucial role in this injury. We investigated the effects of kidney IR on pancreatic exocrine and endocrine functions, antioxidant enzyme activity, and apoptosis.

Material and methods: The protective effect of vitamin C was also investigated. The animals were submitted to non-traumatic bilateral renal IR, sham operation or treatment with vitamin C after IR. Rats were sacrificed on the 1(st), 3(rd), and 7(th) days of the experiment to evaluate the parameters of oxidative stress (catalase, lipid peroxidase, reduced glutathione and superoxide dismutase), pancreatic endocrine and exocrine function (amylase, insulin and fasting blood glucose), renal functions (serum creatinine and blood urea nitrogen), cellular injury and apoptotic markers (Bcl-2, Bax and caspase-3).

Results: Kidney I/R significantly increased the renal and pancreatic functions at 1, 3 and 7 days, while fasting insulin was significantly increased at day 3 after ischemia. Moreover, I/R significantly increased the studied oxidative stress markers and decreased the antioxidant capacity in pancreatic tissues. In addition, renal I/R induced numerous histopatological lesions in pancreatic tissues and increased the apoptosis-related genes. Treating the rats with vitamin C (100 mg/kg) significantly restored the renal and pancreatic functions, improved the pancreatic antioxidant capacity and protected the pancreatic tissues from apoptotic necrosis.

Conclusions: The results suggested that bilateral renal ischemia for 45 min caused significant impairment of pancreatic function and structure as indicators of acute pancreatitis. While IR enhances oxidative stress and apoptosis, vitamin C appears to play a cytoprotective role.

Keywords: kidney ischemia-reperfusion; oxidative stress; pancreatic apoptosis.

Figure 1

Pancreatic oxidative stress level in the study groups: A – catalase, B – lipid peroxidase, C – reduced glutathione, D – SOD. All data are expressed as mean ± SD and were analyzed using one-way ANOVA and Bonferroni post-hoc test *Compared to sham group at p < 0.05. ^†Compared to I/R group at p < 0.05.

Figure 2

Microphotographs in pancreatic tissue of sham, ischemic and treated groups at day 1, day 3 and day 7 of the experiment (H + E, 400×). Sham group shows normal pancreatic tissue. I/R group shows moderate to severe pathological changes. Treated group shows mild pathological changes E – edema, L – leucocytic infiltration, V – vacuolization.

Figure 3

A – Microphotographs showing immunostaining for Bcl-2, Bax and caspase-3 in the sham, I/R and treated groups at day 7 of the experiment (IHC, 400×). B – IOD of Bcl-2, Bax and caspase-3 immunohistochemical intensity was quantified by Image-Pro Plus 0.6 software

Figure 4

Mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) in the experimental groups. A – mtDNA of the experimental groups, lane 1: intact mtDNA isolated from sham group; lane 2: mtDNA samples isolated from I/R group; lanes 3, 4, 5: mtDNA samples isolated from treated groups; B – integrity of nDNA of the experimental groups. Lane M, 1 kb DNA ladder; lane 4, intact nDNA isolated from sham group; lane 1, lane 2 and lane 3, nDNA sample isolated from treated groups; lane 5, nDNA isolated from I/R group