Reperfusion Does Not Induce Oxidative Stress but Sustained Endoplasmic Reticulum Stress in Livers of Rats Subjected to Traumatic-Hemorrhagic Shock

Abstract

Oxidative stress is believed to accompany reperfusion and to mediate dysfunction of the liver after traumatic-hemorrhagic shock (THS). Recently, endoplasmic reticulum (ER) stress has been suggested as an additional factor. This study investigated whether reperfusion after THS leads to increased oxidative and/or ER stress in the liver. In a rat model, including laparotomy, bleeding until decompensation, followed by inadequate or adequate reperfusion phase, three time points were investigated: 40 min, 3 h, and 18 h after shock. The reactive oxygen and nitrogen species and its scavenging capacity (superoxide dismutase 2), the nitrotyrosine formation in proteins, and the lipid peroxidation together with the status of endogenous antioxidants (alpha-tocopherylquinone-alpha-tocopherol ratio) were investigated as markers for oxidative or nitrosylative stress. Mitochondrial function and cytochrome P450 isoform 1A1 activity were analyzed as representatives for hepatocyte function. Activation of the inositol-requiring enzyme 1/X-box binding protein pathway and up-regulation of the 78-kDa glucose-regulated protein were recorded as ER stress markers. Plasma levels of alanine aminotransferase and Bax/Bcl-XL messenger RNA (mRNA) ratio were used as indicators for hepatocyte damage and apoptosis induction. Oxidative or nitrosylative stress markers or representatives of hepatocyte function were unchanged during and short after reperfusion (40 min, 3 h after shock). In contrast, ER stress markers were elevated and paralleled those of hepatocyte damage. Incidence for sustained ER stress and subsequent apoptosis induction were found at 18 h after shock. Thus, THS or reperfusion induces early and persistent ER stress of the liver, independent of oxidative or nitrosylative stress. Although ER stress was not associated with depressed hepatocyte function, it may act as an early trigger of protracted cell death, thereby contributing to delayed organ failure after THS.

Effect of Estrogen on Mitochondrial Function and Intracellular Stress Markers in Rat Liver and Kidney following Trauma-Hemorrhagic Shock and Prolonged Hypotension

“…However, GRP78 mRNA was not yet upregulated. In a different model of T-H, we have shown previously that splicing of XBP1 mRNA already was evident during reperfusion, while GRP78 mRNA was upregulated only after full reperfusion (19). Both markers remained elevated until 18 hours after shock and were associated with a proapoptotic phenotype, suggesting unresolved ER stress and dysfunction (18).…”

“…T-H and resuscitation have been shown to induce ER stress (16,19). The GRP78 (also called BiP) is a chaperone and a key protein in ER stress that triggers UPR upon binding to three specific stress sensors, IRE1, PERK and activating transcription factor 6 (ATF6), and simultaneously to unfolded proteins.…”

“…Respiratory parameters of mitochondria were determined in rat liver homogenates containing mitochondria with a Clark-type oxygen electrode apparatus (Oroboros Ltd., Innsbruck, Austria) as described previously (19). Considering that a population of mitochondria can be lost during the isolation process, we performed these measurements in tissue homogenates without isolating mitochondria.…”

Preservation of hepatic blood flow by direct peritoneal resuscitation improves survival and prevents hepatic inflammation following hemorrhagic shock

“…Even short periods of hypoxia can reduce ATP production, which can lead to failure of the Na ϩ /K ϩ pump (22,24,38). This failure produces hepatocellular swelling and stress-induced unfolding of endoplasmic reticulum proteins, which might initiate hepatocyte apoptosis (6,23). Hepatic cell death and necrosis release HMGB1 into the systemic circulation (4, 8, 30).…”

Central role for MCP-1/CCL2 in injury-induced inflammation revealed by in vitro, in silico, and clinical studies

“…Hypoxic stress, however, is but one of a variety of stresses (e.g. endoplasmic reticulum stress and autophagy) encountered by hepatocytes in settings such as T/HS [22] and I/R [23]. We therefore reasoned that the analysis of synthesis and secretion of inflammatory mediators by stressed hepatocytes would help in our understanding of the pathophysiology of T/HS and other conditions characterized, at least in part, by hepatic stress.…”