Carbon tetrachloride induced hepatorenal toxicity in rats: possible protective effects of wild Pleurotus tuber-regium

Carbon tetrachloride is a reference toxicant in mammalian systems with established toxicities in the kidney, liver, testis, heart, lungs etc. [17, 18]. Once injected into a mammalian system, it undergoes extensive biotransformation in the livers P-450 system to generate trichloromethyl radical (CCl₃°) and chloride radical Cl° which being electron deficient, have very high affinity for electrons in biological tissues. This extortion of electrons from biological systems leads to peroxidation of proteins, distortion of enzymes and DNA [19]. In this study, we tested the hypothesis that wild edible mushrooms like P.tuber-regium could protect against CCl₄ induced hepato-renal toxicity.

Administration of CCl₄ resulted in significant (p??0.05) increases in both the absolute and relative weights of the liver and kidney when compared with the control. This increase in liver and kidney weights may be attributed to lesions and injuries associated with xenobiotics [2] like CCl₄ which peroxidizes cell proteins thereby activating the inflammatory pathway. This is evident from the photomicrographs of both the kidneys and liver that showed proliferation of the bile ducts, tubules and the glomeruli. The enlargement of the liver and kidney were significantly reduced in the treatment groups that received P.tuber-regium suggesting that the mushroom contains some protective phytomedicinals. This result is in agreement with other works on mushrooms in a free radical mediated injury where mushroom reduced oxidative stress mediated injury by gentamicin [2].

The treatment of rats with CCl₄ caused a significant increase in the serum levels of liver and kidney biomarkers like Bilirubin, Creatinin, Urea, Fasting blood glucose FBG, ALT, AST and ALP. The implication of these observations is possible hepato-renal dysfunction as a result of the free radicals; trichloromethyl radical (CCl₃°), trichloromethylperoxy radical (OOCCl₃°), chloride radical (Cl°) etc. generated by the CCl₄ following biotransformation by CYP 2E1 of the liver [20]. These radicals being electron deficient react with electron rich proteins to cause peroxidation of macromolecules like the membranes with subsequent leakage of the enzymes into the serum [21]. Some of these leaked enzymes found in the serum like ALT, AST and ALP are biomarkers of liver that is elevated during hepatotoxicity. This result is agreement with other works that had recorded elevated serum levels of liver markers following CCl₄ intoxication [22]. These elevated biomarkers of liver toxicity were markedly reduced by the administration of P.tuber-regium in a dose dependent manner. P.tuber-regium is known to be rich in antioxidant molecules like phenolics, tannins, flavonoids [22] which are efficient electron donor thereby helping to terminate free radical reaction. This process spares the body’s antioxidant systems and macromolecules which are the primary targets of peroxidation. The protective effect in the liver is also seen in the photomicrographs with well-preserved structures comparable to untreated control group.

The protective activity of P.tuber-regium seen in the liver was also seen in the kidney. The major renal biomarkers suggested significant renoprotection in a dose dependent manner after administration P.tuber-regium, which may be due to anti- oxidative stress mechanism [23]. The significant increase in SOD and decrease in MDA following P.tuber-regium administration in CCl4 treated animals lend credence to the antioxidant potential of this mushroom and its folkloric use. The oxidation of membrane lipid bilayer affected lipid structures of the nephron which resulted in a subcellular structural damage as revealed by the micrographs of the kidney (tubular and glomerular fibrosis). These finding are similar to the protection observed with Digera muricata where the structural changes observed in CCl₄ group were attenuated [24]. This hepato-renal protective effectof P.tuber-regium may be due to the presence of antioxidant phytochemicals that may not only attenuate the toxicity of CCl₄ but may have restorative properties.

The histopathological findings have provided direct evidence of the possibility of the P.tuber-regium to attenuate the disruption of structure of both the liver and kidney cells. These observations complemented the results of the cytoplasmic enzymes namely (alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and bilirubin, creatinine and urea concentrations. A direct radical-scavenging activity of the P.tuber-regium might be involved in the hepato- and nephron- protective activity against CCl₄ exposure.