%0 Journal Article %A Sultana Rekha, Rokeya %A Muvva, SSV Jagadeeswara Rao %A Wan, Min %A Raqib, Rubhana %A Bergman, Peter %A Brighenti, Susanna %A H Gudmundsson, Gudmundur %A Agerberth, Birgitta %D 2015 %T Phenylbutyrate induces LL-37-dependent autophagy and intracellular killing of Mycobacterium tuberculosis in human macrophages %U https://tandf.figshare.com/articles/journal_contribution/Phenylbutyrate_induces_LL_37_dependent_autophagy_and_intracellular_killing_of_i_Mycobacterium_tuberculosis_i_in_human_macrophages/1495517 %R 10.6084/m9.figshare.1495517.v5 %2 https://tandf.figshare.com/ndownloader/files/2191748 %K antimicrobial peptides %K cathelicidin %K innate immunity %K P2RX7 %K tuberculosis %K vitamin D %X

LL-37 is a human antimicrobial peptide (AMP) of the cathelicidin family with multiple activities including a mediator of vitamin D-induced autophagy in human macrophages, resulting in intracellular killing of Mycobacterium tuberculosis (Mtb). In a previous trial in healthy volunteers, we have shown that LL-37 expression and subsequent Mtb-killing can be further enhanced by 4-phenylbutyrate (PBA), also an inducer of LL-37 expression. Here, we explore a potential mechanism(s) behind PBA and LL-37-induced autophagy and intracellular killing of Mtb. Mtb infection of macrophages downregulated the expression of both the CAMP transcript and LL-37 peptide as well as certain autophagy-related genes (BECN1 and ATG5) at both the mRNA and protein levels. In addition, activation of LC3-II in primary macrophages and THP-1 cells was not detected. PBA and the active form of vitamin D3 (1,25[OH]2D3), separately or particularly in combination, were able to overcome Mtb-induced suppression of LL-37 expression. Notably, reactivation of autophagy occurred by stimulation of macrophages with PBA and promoted colocalization of LL-37 and LC3-II in autophagosomes. Importantly, PBA treatment failed to induce autophagy in Mtb-infected THP-1 cells, when the expression of LL-37 was silenced. However, PBA-induced autophagy was restored when the LL-37 knockdown cells were supplemented with synthetic LL-37. Interestingly, we have found that LL-37-induced autophagy was mediated via P2RX7 receptor followed by enhanced cytosolic free Ca2+, and activation of AMPK and PtdIns3K pathways. Altogether, these results suggest a novel activity for PBA as an inducer of autophagy, which is LL-37-dependent and promotes intracellular killing of Mtb in human macrophages.

%I Taylor & Francis