Oxidative stress and apoptosis are proposed mechanisms of cellular injury in studies of xenobiotic hepatotoxicity. This study is focused on addressing the mutual relationship and early signals of these mechanisms in the D-galactosamine and lipopolysaccharide (D-GalN/LPS) hepatotoxicity model, with the help of standard liver function and biochemistry tests, histology, and measurement of gene expression by RT-PCR. Intraperitoneal injection of 400 mg/kg D-GalN and 50 μg/kg LPS was able to induce hepatotoxicity in rats, as evidenced by significant increases in liver enzymes (ALT, AST) and raised bilirubin levels in plasma. Heme oxygenase-1 and nitric oxide synthase-2 gene expressions were significantly increa sed, along with levels of their products, bilirubin and nitrite. Th e gene expression of glutathione peroxidase 1 remained unchanged, whereas a decrease in superoxide dismutase 1 gene expression was noted. Furthermore, the significant increase in the gene expression of apoptotic genes Bid, Bax and caspase-3 indicate early activation of apoptotic pathways, which was confirmed by histological evaluation. In contrast, the measured caspase-3 activity remained unchanged. Overall, the results have revealed differential oxidative stress and apoptotic responses, which deserves further investigations in this hepatotoxicity model., N. Lekić ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
We have analyzed the influence of altered thyroid hormone levels on changes of MyHC protein isoforms and their mRNA transcripts in the soleus muscle of 2-, 4- and 7-month-old euthyroid (EU), hypothyroid (HY) and hyperthyroid (TH) female inbred Lewis strain rats (methimazole and T3 treatment started 3 to 4 weeks after birth). We have found that the content of the dominant MyHC 1 isoform gradually increased in the EU rats and that this increase was more progressive in the HY rats at all three stages. On the other hand, in the TH rats the content of MyHC 1 isoform was the highest in the 2-month-old rats and it decreased with an increasing length of T3 treatment. The content of the minor 2a MyHC isoform followed the opposite pattern. In contrast to the protein isoforms, the MyHC mRNA transcripts remained at similar levels. Nevertheless, in general, the MyHC 1 mRNA level was decreased and MyHC 2a transcript increased in the TH rats, while the opposite changes occurred in the HY rats. Our results thus suggest that in the rat soleus muscle, both increased and decreased levels of thyroid hormones speed up the formation of an adult slow phenotype which is demonstrated by the precocious appearance of the slow MyHC 1 isoform, but opposite to the hypothyroid status, a longer T3 application promotes the expression of the faster MyHC 2a isoform., A. Vadászová-Soukup, T. Soukup., and Obsahuje bibliografii a bibliografické odkazy
We have studied the effect of chronic thyroid status alterations on the myosin heavy chain (MyHC) isoform composition (by SDS-PAGE) and on MyHC mRNA levels (by RT-PCR) in the fast extensor digitorum longus (EDL)
muscle of 7-month-old inbred Lewis strain female rats and compared this with corresponding results of the previously studied slow soleus muscle. Our findings show that in the EDL muscle, all four types 1, 2a, 2x/d and 2b of MyHC mRNA transcripts and protein isoforms are present in euthyroid, hypothyroid and hyperthyroid rats, i.e. after chronic
treatment with methimazole and T3, respectively. This is in contrast with the soleus, where only MyHC1 and 2a protein isoforms are expressed under similar conditions. Except for 2x/d MyHC mRNA transcripts in the EDL muscles, there was always significant difference between hypothyroid and hyperthyroid rats both at mRNA and protein levels. From our results we can conclude that extended alteration of the thyroid status leads to typical changes in the expression of MyHC mRNA transcripts and MyHC protein isoforms in the fast EDL and the slow soleus muscles. These changes
correspond to those described after shorter periods of altered thyroid status. The characteristic phenotype differences between soleus and EDL muscles remain, however, preserved even after 7 months of thyroid hormone status alteration.