Kupffer Cells Protect Liver from Ischemia-Reperfusion Injury by an Inducible Nitric Oxide Synthase-Dependent Mechanism

Abstract

The aim of this study was to investigate the role of nitric oxide (NO) in rat hepatic ischemia-reperfusion (I/R) injury. Animals were divided into four groups: Group I, control; Group II, gadolinium chloride (GdCl3), a Kupffer cell depleting agent, pretreated; Group III, S-methylisothiourea (SMT), a potent inducible NO synthase (iNOS) inhibitor, pretreated; Group IV, pretreated with SMT, then treated with S-Nitroso-N-acetylpenicillamine (SNAP), a NO donor, after ischemia. Sprague-Dawley rats underwent left lateral and median lobe ischemia for 60 min and reperfusion for 120 min. The left lateral and median lobes were used as ischemic lobes, and the right lateral lobe in the same rat was used as a control lobe. The total NOS (tNOS), iNOS, constitutive NOS (cNOS) activity, and liver protein were determined. The liver tissue malonaldehyde (MDA) level was measured as an index of lipid peroxidation. Liver histology was also examined. The liver tNOS activity in ischemic lobes of Group I, II, III, and IV was increased by 214%, 86%, 61%, and 45%, respectively. The increase in tNOS activity is mainly due to the induction of iNOS activity in the ischemic lobes of rat liver. GdCl3 significantly decreased the tNOS by 66% in the ischemic lobes. GdCl3 significantly increased MDA by 39% in the ischemic lobes. SMT significantly decreased tNOS and iNOS activity by 66% and 85% in ischemic lobes. SMT increased MDA by 67% in the ischemic lobes. SMT + SNAP treatment increased iNOS activity by 117% in the ischemic lobes in comparison with the ischemic lobes of the SMT group. SMT + SNAP treatment decreased MDA by 39% in the ischemic lobes. SMT + SNAP treatment also decreased the sinusoidal congestion and spotty necrosis of hepatocytes in the ischemic lobes. iNOS immunostaining showed an obvious increase in sinusodial area of the ischemic lobes where most Kupffer cells were interspersed. In conclusion, in this model of liver I/R injury, I/R increased the activity of tNOS and iNOS, but not the cNOS activity. Kupffer cells might be the major source of the induction of iNOS activity. The iNOS specific inhibitor SMT increased the lipid peroxidation and the tissue damage in hepatic I/R injury. On the contrary, the NO donor SNAP increased the activity of iNOS and decreased the hepatic injury in this study. Kupffer cells could protect liver from I/R injury by an iNOS-dependent mechanism, thus NO production has a beneficial role in hepatic IR injury.

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

“…Complicated mechanisms and numerous molecules are involved in exerting the protective effects of NO against liver IRI, including ATP molecules, endothelin, adhesion molecules, cytokines, free radical species, and antioxidants [33] (Figure 2). NO has been shown to potentiate hepatic ATP levels, reduce oxidative damage, prevent the reduction of antioxidants such as glutathione, and reduce the adverse effects of endothelin during liver IRI [33,34] . Studies have demonstrated that NO affects cellular decisions of life and death by either turning on or shutting off apoptotic pathways, suggesting that NO can function differently depending on the dose and duration of exposure [35,36] .…”

Beneficial effects of rutin andl-arginine coadministration in a rat model of liver ischemia-reperfusion injury

“…On the other hand, in response to enhancement of oxidative stress, cells undergo specific changes in enzyme activities, cytoskeletal structure, membrane transport, antioxidant defenses, and induction of heat shock protein, among which heme oxygenase (HO)-1 is believed to play a key role (14,37). The HO system is among the most critical of the cytoprotective mechanisms activated during cellular stress, hyperthermic preconditioning, or long-term fasting, exerting antioxidant and anti-inflammatory functions, acting as a molecular chaperon, modulating cell cycle, and maintaining microcirculation (3,9,20).…”

Src family kinases regulate p38 MAPK-mediated IL-6 production in Kupffer cells following hypoxia

“…There is growing evidence that Kupffer cells play a critical role in regulating immune functions following trauma (25,29). Located in the liver sinusoids, Kupffer cells represent the largest population of tissue-fixed macrophages in the body and play a key role in the recognition and eventual clearance of bacteria from the blood (46).…”