Injection of rHuEPO enhance recovery from CP-induced AKI in rats by ameliorating renal functional impairment and exerting important anti-apoptotic effects. However, rHuEPO inhibited CP-induced AKI by a possible mechanism involving PI3K/Akt activation and the inhibition of ER stress-mediated apoptosis.

Microcystins (MCs) are a group of cyclic hepatotoxic peptides produced by cyanobacteria. Microcystin-LR (MC-LR) contains Leucine (L) and Arginine (R) in the variable positions, and is one of the most common and potently toxic peptides. MC-LR can inhibit protein phosphatase type 1 and type 2A (PP1 and PP2A) activities and induce excessive production of reactive oxygen species (ROS). The underlying mechanism of the inhibition of PP1 and PP2A has been extensively studied. The over-production of ROS is considered to be another main mechanism behind MC-LR toxicity; however, the detailed toxicological mechanism involved in over-production of ROS in carp (Cyprinus carpio L.) remains largely unclear. In our present study, the hydroxyl radical (•OH) was significantly induced in the liver of carp after a relatively short-term exposure to MC-LR. The elevated reactive oxygen species (ROS) production may play an important role in the disruption of microtubule structure. Pre-injection of the antioxidant N-acetyl-cysteine (NAC) provided significant protection to the cytoskeleton, however buthionine sulfoximine (BSO) exacerbated cytoskeletal destruction. In addition, the elevated ROS formation induced the expression of apoptosis-related genes, including p38, JNKa, and bcl-2. A significant increase in apoptotic cells was observed at 12 - 48 hours. Our study further supports evidence that ROS are involved in MC-LR induced damage to liver cells in carp, and indicates the need for further study of the molecular mechanisms behind MC-LR toxicity.

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Myoglobin plays an important role in rhabdomyolysis‐induced acute kidney injury (AKI), but the underlying mechanisms are still unclear. The present study investigates myoglobin‐induced apoptosis in HK‐2 cells (human renal proximal tubule cells) to discover some of the mechanisms involved in rhabdomyolysis related AKI. Metmyoglobin is reduced to ferrous myoglobin by ascorbic acid, and then the HK‐2 cells are incubated with ferrous myoglobin. Cell viability is measured by 3‐(4,5)‐dimethylthiahiazo(‐z‐y1)‐3,5‐di‐phenytetrazoliumromide (MTT) assay, and cell injury is tested by supernatant lactose dehydrogenase (LDH). Cell apoptosis is evaluated by fluorescent microscopy of Hoechst staining and by flow cytometry of Annexin V/PI double staining. The apoptosis related protein expression is determined by Western blot. HK‐2 cells were incubated with 200 µM ferrous myoglobin for 24 h, the cell viability decreased and supernatant LDH release increased. Hoechst staining indicated more apoptosis after incubation. Molecular chaperone glucose‐related protein 78 (GRP78), cytochrome C, caspase‐9 started to increase within 3 h after incubation while caspase‐4, caspase‐8 showed no significant change. (iii) When the inositol triphosphate receptor (IP3R) calcium channel was blocked by 2‐aminoethoxydiphenyl‐borinate (2‐APB), caspase‐9 was completely inhibited, GRP78 and caspase‐4 increased dramatically, and caspase‐3 expression was not affected. The apoptosis in HK‐2 cells showed no significant change. Apoptosis in HK‐2 cells incubated with ferrous myoglobin is an endoplasmic reticulum stress induced, IP3R calcium channel mediated, caspase‐9 dependent intrinsic pathway. When the intrinsic pathway was inhibited using an IP3R calcium channel blocker, endoplasmic reticulum stress increased, resulting in the activation of caspase‐4 that cleaved caspase‐3 and generated a substitutive pathway of apoptosis.