title: AMPK activation by metformin inhibits local innate immune responses in the isolated rat heart by suppression of TLR 4-related pathway.
abstract: Toll like receptors (TLRs) are key players in the innate immune responses. The energy sensing enzyme, AMPK, has been implicated in the modulation of immunity. The present study investigated whether AMPK activation by metformin could contribute to the regulation of immune responses in the isolated heart via suppression of TLR4 activity, independent of circulatory immunity. Isolated Wistar rat hearts were perfused with Krebs-Henseleit buffer in the absence or presence of lipopolysaccharide (LPS; 0.2μM), LPS+metformin (10mM), and LPS+metformin+compound C (10μM). Following measurement of hemodynamic parameters, TLR4-activation related changes and TLR4 mRNA level in the heart was examined by western blotting and real-time PCR. The activation of AMPK was evaluated by measuring the ratio of p-AMPKα and p-ACC to their non-phosphorylated forms. The effluent and cardiac levels of TNF-α and IL6 were assayed by ELISA. LPS profoundly increased the levels of TLR4 mRNA, MyD88 (TLR4 adaptor protein), and NF-κB and also the release of TNF-α and IL6 from the heart. The enhancement in the TLR4 activity was associated with a significant depression of myocardial function. Metformin clearly augmented the phosphorylation of both AMPKα and ACC and in addition to improvement of cardiac performance, markedly suppressed the TLR4 activity. Antagonizing AMPK by compound C which is a selective inhibitor of AMPK pathway, considerably reversed the protective effects of metformin against the TLR4-related activity. The results of the study demonstrated the importance of TLR4-involved local immune responses in the LPS-induced myocardial dysfunction and indicated a clear link between AMPK and TLR4.
authors.affiliation: Department of Pharmacology, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran; Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Haleh
authors.initials: H
authors.lastname: Vaez
authors.affiliation: Department of Pharmacology, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Moslem
authors.initials: M
authors.lastname: Najafi
authors.affiliation: Department of Pharmacology, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Maryam
authors.initials: M
authors.lastname: Rameshrad
authors.affiliation: Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Negisa Seyed
authors.initials: NS
authors.lastname: Toutounchi
authors.affiliation: Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Mehraveh
authors.initials: M
authors.lastname: Garjani
authors.affiliation: Research Center for Pharmaceutical Nanotechnology, Tabriz University of Medical Sciences, Tabriz, Iran.
authors.forename: Jaleh
authors.initials: J
authors.lastname: Barar
authors.affiliation: Department of Pharmacology, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran; Cardiovascular Research Center, Tabriz University of Medical Sciences, Tabriz, Iran. Electronic address: garjania@tbzmed.ac.ir.
authors.forename: Alireza
authors.initials: A
authors.lastname: Garjani
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D007113:Immunity, Innate / Q000187:drug effects; D015850:Interleukin-6 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000276:immunology; D008297:Male; D008687:Metformin / Q000494:pharmacology*; D009206:Myocardium / Q000276:immunology*; D016328:NF-kappa B / Q000378:metabolism; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D015850:Interleukin-6; D008070:Lipopolysaccharides; D016328:NF-kappa B; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D008687:Metformin; D055372:AMP-Activated Protein Kinases
keywords: AMPK; Heart; Metformin; NF-κB; Toll-like receptor 4