Mice Liver Nucleotides Pool, The Characteristics Of The Nucleic Acid Pool And Its Relationship With The Role Of Fibrosis

Hepatic fibrosis occurs during most chronic hepatic diseases and ultimately leads to cirrhosis. So far the achievements obtained in revealing the mechanisms of fibrosis at the level of cell and biomacromolecule has been tremendous. However, our knowledge about the properties and dynamic of the small molecule pools such as nucleotide pool as well as their effects on fibrosis and interaction with biomacromolecule during liver’s fibrosis progression is still very poor. The aim of this study is to investigate the properties and the dynamic of the nucleotide pools and its interacting relationship with the differentially expressed transcriptome as well as with the fibrosis progression in mice liver so that some new insights both into the fibrosis mechanism and into the fibrosis-alleviating mechanism by exogenous nucleotides administration are expected to be provided.In this study we established the hepatic fibrosis model of CCl4-induced mice, examined the fibrosis progression with AST、ALT and histological assessment, detected the contents of nucleotides in livers of both CCl4-induced and control mice with HPLC systematically. Representative data of differentially expressed transcriptome of CCl4-induced mice were screened from BioGPS database and literatures in the study. Also we detected the expression level of five key enzymes in nucleotide metabolism and seven important genes in hepatic fibrosis with qPCR. The NMP contents, the AST/ALT ratios and the representative data of differentially expressed genes were used to analyze the relationship between nucleotide pool and differentially expressed transcriptome as well as between nucleotide pool and fibrosis progression through the correlation analysis.The AST and ALT value continued decrease in CCl4-induced group but they were significantly higher than the ones in control group. At8week, the AST/ALT value was greater than1while the hepatic was seriously hurt. The histological evaluation by light microscopy of livers from treated animals produced moderate hepatic necrosis and fibrosis with only slight fatty accumulation and inflammation. At8weeks, micronodular cirrhosis was already established. No histological abnormalities were detected in control group. The histological result was similar with the trend of AST/ALT value in CCl4-induced group.The performance of nucleotide pool of CCl4-induced livers differed a great deal from that of control livers, the total nucleotides contents of increased all over the experiment while the ones of control mice maintained relatively stable. Both the contents of total nucleotides and NMP in CCl4-induced mice were significantly lower than those in normal mice at early hepatic injury phase while significantly higher than those in normal mice at hepatic fibrosis phase, in another words, both the contents of total nucleotides and NMP in CCl4-induced liver increased continuously while those in normal liver kept almost stable. The contents of nucleotides in CCl4-induced liver rank was NMP>>NDP>NTP.The AMP content of treat group continued to increase and it was significantly lower than that of control group (p<0.05) at2week while after6week the one was higher than in control group and it was significantly higher than that of control group (p<0.01) at10week. The content of ADP in treat group was significantly lower than that of control group (p<0.01) at2week while significantly higher than that of control group (p<0.01) at10week. After4week, the content of ADP continued to increase. The content of ATP had no significantly difference between treat group and control group over time. The GMP contents of treat group also continued to increase, and at6week and10week it significantly higher than that of control group (p<0.01) while in other sampling times it had no significantly difference. The content of GDP in treat group was significantly lower that of control group (p<0.01) at4week while significantly higher than that of control group (p<0.01) at10week.In other sampling times, it had no significantly difference between treat group and control group. The UMP contents of treat group was significantly lower than that of control group at2week (p<0.05) and4week (p<0.01) while significantly higher than that of control group (p<0.01) at6week and10week. At8week, it had no significantly difference between treat group and control group. The content of UTP kept increasing in treat group slowly. And it was significantly lower than that of control group (p<0.01) at2week and8week while it had no significantly difference in other sampling times. Only CMP content of treat group was increased at beginning and then decreased. It was significantly lower than that of control group (p<0.01) at4week while significantly higher than that of control group (p<0.01) at8week and10week. In other sampling times, it had no significantly difference between treat group and control group.The differential expressed transcriptome showed that in fibrosis mice the down-regulated genes dominated more than the up-regulated genes at early hepatic injury phase while the trend changed opposite in fibrosis phase. The variable quantity of NMP within the nucleotide pool and the counterpart of differentially transcriptome of CCl4-induced mice displayed a significantly positive correlation with the correlation coefficient as0.927(p<0.05) at two-tailed. Furthermore, the NMP content was highly associated with the fibrosis index (AST/ALT ratios) with the correlation coefficient as0.904(p<0.05) at two-tailed.The expression level of key enzymes of nucleotide metabolism which contained de novo pathway and degradation pathway had no significantly difference between the two groups. But the adenine phosphoribosyl transferase (Aprt) in salvage pathway changed significantly. The expression level of seven fibrosis related genes changed in treated mice and these results were concordant with the finding obtained in published literaturesThe performance of liver’s nucleotide pool has a significant effect on liver’s ongoing physiology, and the changing nucleotide pool, the differentially expressed genes, and the interaction of the two each play an important role in liver’s fibrosis progression. Moreover, this discovery may provide some new explanations to why exogenous nucleotides could alleviate hepatic fibrosis.