Pyruvate attenuates myoglobin in vitro toxicity

Role of Free Radicals and Biotransformation in Trichloronitrobenzene-Induced Nephrotoxicity In Vitro

This study determined the comparative nephrotoxic potential of four trichloronitrobenzenes (TCNBs) (2,3,4-; 2,4,5-; 2,4,6-; and 3,4,5-TCNB) and explored the effects of antioxidants and biotransformation inhibitors on TCNB-induced cytotoxicity in isolated renal cortical cells (IRCC) from male Fischer 344 rats. IRCC were incubated with a TCNB up to 1.0 mM for 15–120 min. Pretreatment with an antioxidant or cytochrome P450 (CYP), flavin monooxygenase (FMO), or peroxidase inhibitor was used in some experiments. Among the four TCNBs, the order of decreasing nephrotoxic potential was approximately 3,4,5- > 2,4,6- > 2,3,4- > 2,4,5-TCNB. The four TCNBs exhibited a similar profile of attenuation of cytotoxicity in response to antioxidant pretreatments. 2,3,4- and 3,4,5-TCNB cytotoxicity was attenuated by most of the biotransformation inhibitors tested, 2,4,5-TCNB cytotoxicity was only inhibited by isoniazid (CYP 2E1 inhibitor), and 2,4,6-TCNB-induced cytotoxicity was inhibited by one CYP inhibitor, one FMO inhibitor, and one peroxidase inhibitor. All of the CYP specific inhibitors tested offered some attenuation of 3,4,5-TCNB cytotoxicity. These results indicate that 3,4,5-TCNB is the most potent nephrotoxicant, free radicals play a role in the TCNB cytotoxicity, and the role of biotransformation in TCNB nephrotoxicity in vitro is variable and dependent on the position of the chloro groups.

Rhabdomyolysis induced AKI via the regulation of endoplasmic reticulum stress and oxidative stress in PTECs

Mechanism for the role of ER stress and oxidative stress activation in rhabdomyolysis-associated AKI.

Pyruvate alleviates lipid peroxidation and multiple-organ dysfunction in rats with hemorrhagic shock

OBJECTIVE

Pyruvate can reduce lipid peroxidation, which plays a critical role in organ injury, in various models. However, it is not fully understood if this inhibition occurs in resuscitation of hemorrhagic shock (HS). This study examines effects of pyruvate Ringer solution (PR) in this respect in rats.

METHODS

Rats, subjected to 45% blood loss, were randomly allocated to the 3 groups (n = 18): HS with no fluid resuscitation (group NR), HS resuscitated with lactated Ringer solution (LR) (group LR), and HS resuscitated with PR (group PR). Mean arterial pressure, plasma levels of thiobarbituric acid reactive substances (TBARS), and superoxide dismutase were measured at various time points until 360 minutes after hemorrhage. Visceral organs were harvested at the end for evaluations of the TBARS, antioxidant enzyme, and tissue water content. Other 54 rats with identical procedures without sampling were documented for 24-hour survival rates (n = 18) after fluid resuscitation.

RESULTS

Pyruvate Ringer solution significantly increased mean arterial pressure and decreased blood TBARS levels after lethal HS. It also reduced TBARS concentrations and glutathione peroxidase activities but significantly enhanced glutathione reductase activities in most organs and greatly improved the ratios of reduced glutathione over oxidized glutathione in various organs in group PR, compared to group LR. Furthermore, PR significantly improved various organ function and water contents relative to LR. Group PR showed a more than 2-fold higher 24-hour survival rate of group LR.

CONCLUSIONS

Pyruvate Ringer solution alleviated organ edema and injury and prompted survival partially through inhibition of lipid peroxidation in various organs in severe HS rats.

Myoglobin-induced apoptosis: two pathways related to endoplasmic reticulum stress

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.

Effects of pyruvate, succinate, and lactate enhancement on beef longissimus raw color

Beef strip loins (n=30) were divided into halves, and each half was assigned randomly to one of four injection enhancements: (1) non-enhanced control, (2) 3% pyruvate, (3) 3% succinate, and (4) 3% lactate. Steaks were cut and packaged in either vacuum, high oxygen (80% O(2)/20% CO(2)), or PVC. Color and lipid oxidation were measured on days 0, 5, and 13 of storage at 1°C. Enhancement had a significant effect on steak pH. On day 13 of storage, steaks enhanced with lactate, pyruvate, and succinate were less discolored (P<0.05) than control steaks in PVC and high oxygen. Enhancement darkened steaks (P<0.05) compared with control steaks. Succinate had the greatest and pyruvate had the least metmyoglobin-reducing activity (P<0.05). Lactate and pyruvate decreased the TBARS values of steaks packaged in PVC (P<0.05) whereas pyruvate was most effective for lowering lipid oxidation in high-oxygen packaging.

Pyruvate reduces 4-aminophenol in vitro toxicity

Pyruvate has been observed to reduce the nephrotoxicity of some agents by maintaining glutathione status and preventing lipid peroxidation. This study examined the mechanism for pyruvate protection of p-aminophenol (PAP) nephrotoxicity. Renal cortical slices from male Fischer 344 rats were incubated for 30-120 min with 0, 0.1, 0.25 or 0.5 mM PAP in oxygenated Krebs buffer containing 0 or 10 mM pyruvate or glucose (1.28 or 5.5 mM). LDH leakage was increased above control by 0.25 and 0.5 mM PAP beginning at 60 min and by 0.1 mM PAP at 120 min. Pyruvate prevented an increase in LDH leakage at 60- and 120-min exposure to 0.1 and 0.25 mM PAP. Pyruvate also prevented a decline in ATP levels. Glucose (1.28 and 5.5 mM) provided less protection than pyruvate from PAP toxicity. Total glutathione levels were diminished by 0.1 and 0.25 mM PAP within 60 and 30 min, respectively. Pyruvate prevented the decline in glutathione by 0.1 mM PAP at both time periods and at 30 min for 0.25 mM PAP. Pyruvate reduced the magnitude of glutathione depletion by 0.25 mM PAP following a 60-min incubation. Glutathione disulfide (GSSG) levels in renal slices were increased at 60 min by exposure to 0.25 mM PAP, while pyruvate prevented increased GSSG levels by PAP. Pyruvate also reduced the extent of 4-hydroxynonenal (4-HNE)-adducted proteins present after a 90-min incubation with PAP. These results indicate that pyruvate provided protection for PAP toxicity by providing an energy substrate and reducing oxidative stress.