Connectivity mapping of angiotensin-PPAR interactions involved in the amelioration of non-alcoholic steatohepatitis by Telmisartan - PubMed (original) (raw)
Connectivity mapping of angiotensin-PPAR interactions involved in the amelioration of non-alcoholic steatohepatitis by Telmisartan
Jung Gyu Park et al. Sci Rep. 2019.
Abstract
Nonalcoholic fatty liver disease (NAFLD) is a global health problem that is associated with various metabolic disorders. Telmisartan is a potential treatment for NAFLD due to its ability to improve insulin sensitivity and decrease hepatic fat accumulation via modulation of PPARγ, and to suppress hepatic fibrosis by blocking angiotensin II receptors. However, the underlying mechanisms of action of telmisartan have yet to be fully elucidated. In the present study, diabetic nonalcoholic steatohepatitis (NASH) mice (STAM mice) received daily administrations of telmisartan for 6 weeks to assess the improvements in NASH. Hepatic transcriptome analyses revealed that the amelioration of NASH likely occurred through the regulation of inflammatory- and fibrosis-related gene responses. An integrated network analysis including transcriptional and non-transcriptional genes regulated by telmisartan showed that the NAFLD pathway is interconnected with the dysregulated RAS-PPAR-NFκB pathways. The downstream targets of PPARα, PPARδ, and RELA in this network significantly overlapped with telmisartan-induced differentially expressed genes (DEGs), which were verified in palmitate-treated Hepa1c1c7 cell line. This transcriptome approach accompanied with cell-based molecular analyses provided the opportunity to understand the fundamental molecular mechanisms underpinning the therapeutic effects of telmisartan, and will contribute to the establishment of a novel pharmacological treatment for NASH patients.
Conflict of interest statement
The authors declare no competing interests.
Figures
Figure 1
Telmisartan-induced improvements of NASH in STAM mice. Relative liver weights of the mice (a). Triglyceride levels in the liver tissues (b). mRNA expression levels of Tgfb gene (c). NAFLD activity score (d). Lipid accumulation in vehicle- (e) and telmisartan- (f) treated livers and quantification of positive areas (%) of Sirius red in liver tissues (g). Degrees of fibrosis in vehicle- (h) and telmisartan- (i) treated livers and quantification of positive areas (%) of oil red O in liver tissues (j). Images were captured under 200 × magnification. Horizon bars in the box plots indicate mean values and whiskers indicate minimum and maximum values. Bar graph values are presented as means ± standard deviation (SD). n = 7 per group; **p < 0.01, ***p < 0.001 vs. control.
Figure 2
Transcriptional genes-regulated by telmisartan. Unsupervised hierarchical clustering of probes in selected liver tissues (n = 3); veh is vehicle control (black) and Tel is telmisartan treatment (red) (a). DEGs induced by telmisartan in the liver tissues; up-regulated genes were counted in the white area, and down-regulated genes in the gray area, in the pie graph (b). qRT-PCR validation of microarray results. Bar graph values are presented as means ± SD. Grid line indicates _Gapdh_-normalized mRNA level of control. n = 6 per group; *p < 0.05 vs. microarray (c). Biological states or processes down-regulated by telmisartan in the liver tissues; data are presented as –log10 (FDR _q_-value) (d). Enriched gene set in biological states or processes down-regulated by telmisartan (e).
Figure 3
Non-transcriptional genes-regulated by telmisartan. (Left) Connectivity score and rank of pharmacologic; black dotted line indicates pharmacologic perturbagens. (Right) Chemical structures of top ranked pharmacologic perturbagens were depicted and their corresponding target genes were described in parentheses (a). (Left) Connectivity score and rank of genetic perturbagens; blue dotted line indicates genetic perturbagens by knock-down, and red dotted line indicates genetic perturbagens by overexpression. (Right) Strongly paired top ranked genes were depicted. Upper-case characters indicate non-transcriptional genes regulated by telmisartan; lower-case characters indicate transcriptional genes regulated by telmisartan; bold characters indicate strongly paired genes. Interaction between gene products were depicted by edges (b).
Figure 4
Angiotensin-PPAR-NFκB signaling pathway-associated regulatory network induced by telmisartan. STRING PPI network constructed with transcriptional and non-transcriptional genes regulated by telmisartan. Red nodes indicated genes enriched in the NAFLD pathway. Upper-case characters in the nodes indicate non-transcriptional regulated genes from CMap analyses, lower-case characters indicate transcriptional genes regulated by telmisartan (a). Downstream targets of transcription factors in the network. Venn diagram shows direct targets of PPARA in green circle, PPARD in red, or RELA in blue from telmisartan-induced DEGs (b).
Figure 5
Regulation of PPARα, PPARδ, and RELA pathway by telmisartan in lipotoxicity-induced Hepa1c1c7 cells. Western blotting of differentially expressed PPARα, PPARδ, and RELA by telmisartan in Hepa1c1c7 cells with or without palmitate. Expression values were normalized with ACTB. (a). Differential expression of target genes of PPARα, PPARδ, or RELA by telmisartan in Hepa1c1c7 cells with or without palmitate. Expression values were normalized with Gapdh (b). Bar graph values are presented as means ± SD, n = 3; *p < 0.05, **p < 0.01, ***p < 0.001 vs. control; #p < 0.05, ##p < 0.01, ###p < 0.001 vs. palmitate. Ctrl: vehicle control, Tel: telmisartan at 10 µM, Pal: palmitate at 0.2 mM.
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