Role of Tissue Repair in Drug Induced Liver injury [Dili] Model of Female Swiss Albino Mice

Abstract

The liver is the central site for the biotransformation of xenobiotic chemicals and therefore is involved in the detoxifying mechanism of the body. In this process it is exposed to high concentrations of toxicants and toxic metabolites in the blood making it susceptible to injury. The liver is principle organ for the regulation protein, carbohydrate and lipid metabolism. The liver contains parenchymal cell (Hepatocyte) and non-parenchymal cell (Kupffer cell, Ito cell and endothelial cells). The hepatocyte regulates the level of the CYP‘s enzyme which is important for the detoxification process. Liver has a strong potential for regeneration after physical, biological or chemical injury. The stimulation of tissue repair is a biologic response that accompanies injury, quantifying this response in addition to measuring injury might be helpful in predictive toxicology. The hepatocyte regulates the proliferation as well dynamic aspect of liver. Liver injury and tissue repair are simultaneous but opposing parallel responses to administration of toxic chemicals. A wide variety of additional experimental evidence confirms the central role of stimulated tissue repair as a decisive determinant of the final outcome of liver injury inflicted by hepatotoxicants.The drug induced injury (DILI) is more common because of the high exposure to the chemical, drug and their metabolite or even due to drug interaction. The prevalence of drug induced liver injury is about 14% of all liver failure cases. The idiosyncratic nature and poor prognosis of DILI make this type of reaction a major safety issue during drug development, as well as the most common cause for the withdrawal of drugs from the pharmaceutical market. The drug overdose leads to the liver injury and can cause a diverse array of liver injury, which may be acute or chronic. Carbamazepine is well established antiepileptic drug which is having side effect of acute hepatitis and hepatocellular injury at higher dose. The CBZ Induced liver injury model is recently studied for the mechanism of CBZ induced liver injury. But role of tissue repair (liver regeneration) is not reported till-date. Whereas other pharmacological model of DILI like Paracetamol, Thioacetamide and Carbon tetrachloride have already been studied for the role of liver regeneration. So objectives of the present study are - 1. To test weather another strain of mice (Female Swiss Albino) is also susceptible to CBZ induced liver injury. 2. To study the role of liver regeneration (tissue repair) in CBZ induced liver injury model. Mice were divided into two groups like-Vehicle control (VC) and the CBZ treated (CT). Vehicle control group animals were given the vehicle (corn oil) whereas the CBZ treated groups of animal were given carbamazepine (350mg/kg, p.o-4 days & 800mg/kg, p.o. on 5th day) suspended in corn oil. After the 5th day of dosing both blood and liver sample are collected at different time interval like- 0, 12, 24, 36, 48, 72, 96 hrs. Blood sample was used for biochemical analysis i.e. Serum SGOT, SGPT and Glucose level estimation and liver tissue used for liver glycogen and histopathological analysis. The hepatic injury causes the leakage of enzyme from the cell due to altered permeability of membrane resulting in increased level in serum. The early liver injury in CBZ treated group was evident by the elevated level of the SGPT and SGOT enzyme level as compared to the Vehicle control group. The elevation of SGPT and SGOT was gradually increased up to 48 hrs time point. In contrast, no elevation of enzyme levels was observed in Vehicle control group at any time point. The elevated level of the serum SGPT and SGOT level up to 48h indicates maximum tissue injury mediated by the primary and secondary inflammation. The primary inflammation was occurred due to the CBZ and its metabolite i.e. CBZ 10, 11 epoxide and after that the secondary inflammation induced by damage hepatocyte which activate further release of inflammatory mediator. Further the enzymes level was declined at 96 hrs indicate the tissue repair response. The gluconeogenesis and glycogenolysis were simultaneous regulated by the hepatocyte. The levels of glycogen in the hepatocyte and serum glucose indicate injury and energy profile of the hepatic tissue. The level of glucose were elevated up to 24 hrs indicate the liver tissue repair process, that demand energy leading to gradually depletion of glucose as reflected at 36 & 48 hrs time point indicating consumption of energy in the process of tissue repair. The level of glycogen supports the glucose level changes during tissue repair and injury process. The decline was gradually observed up to the 48 hrs time point in CBZ treated group which reflect the increase in demand of energy required for the tissue repair response. The glycogen was converted into the glucose to meet energy requirement, later glycogen levels was elevated up to 96 hrs suggested that tissue repair is almost completed that resulted in stabilization of glycogen level. The proliferation of the cell could be maximum at 36 & 48 hrs as evident from decreased glucose and glycogen levels and thereafter stabilized slowly. The histopathological analysis showed that gradual increase in extent of necrosis as observed up to 0 - 48 hrs time points which support liver injury in CBZ treated mice. Whereas vehicle control mice show normal liver archistructure. The necrosis was maximum at 48 hrs and thereafter decline gradually indicating the completion of tissue repair response. The presence of the apoptotic bodies at 72 and 96 hrs indicates that the tissue repair was terminated at this point or gradual cessation of the proliferation of the cell. The presence of occasional mitosis activity at 36 & 48 hrs reflects tissue repair response at that time point interval. The decline in the necrosis and the reduction in the inflammation, apoptotic bodies showed after 72 hrs indicate that the tissue repair or liver regeneration has been completed at later time point. The histopathology result supports the biochemical data of CBZ induced liver injury. In conclusion, female Swiss albino mice is susceptible to CBZ induced liver injury. This finding suggested that the tissue injury was observed due to the toxic dose of the CBZ. Whereas tissue repair response play an important role in the reversal of CBZ induced liver injury. The elevated level of liver injury markers and histopathological data suggest the liver injury severity, while the presence of the mitotic body, decline of the liver injury markers and consumption of energy substrate indicate that tissue repair has been simultaneously accompanied to regress the liver injury induced by CBZ in female Swiss albino mice.