Entinostat up-regulates the CAMP gene encoding LL-37 via activation of STAT3 and HIF-1α transcription factors

Abstract

Bacterial resistance against classical antibiotics is a growing problem and the development of new antibiotics is limited. Thus, novel alternatives to antibiotics are warranted. Antimicrobial peptides (AMPs) are effector molecules of innate immunity that can be induced by several compounds, including vitamin D and phenyl-butyrate (PBA). Utilizing a luciferase based assay, we recently discovered that the histone deacetylase inhibitor Entinostat is a potent inducer of the CAMP gene encoding the human cathelicidin LL-37. Here we investigate a mechanism for the induction and also find that Entinostat up-regulates human β-defensin 1. Analysis of the CAMP promoter sequence revealed binding sites for the transcription factors STAT3 and HIF-1α. By using short hairpin RNA and selective inhibitors, we found that both transcription factors are involved in Entinostat-induced expression of LL-37. However, only HIF-1α was found to be recruited to the CAMP promoter, suggesting that Entinostat activates STAT3, which promotes transcription of CAMP by increasing the expression of HIF-1α. Finally, we provide in vivo relevance to our findings by showing that Entinostat-elicited LL-37 expression was impaired in macrophages from a patient with a STAT3-mutation. Combined, our findings support a role for STAT3 and HIF-1α in the regulation of LL-37 expression.

Potent Inducers of Endogenous Antimicrobial Peptides for Host Directed Therapy of Infections

“…In addition, induction with different classes of compounds can give increased levels of a mixture of several antimicrobial components, including several AMPs 31. For example, in our parallel mechanistic study we have also shown induction of human β-defensin 1 by compound 5 23. Additional antimicrobial components will contribute to a parallel attack on the microbe, which makes it more difficult to develop resistance.…”

“…Although some induction is likely to occur due to HDAC inhibition the results suggest that the main mechanism for induction with APD’s is not gene activation through inhibition of histone deacetylation but through other mechanisms. We have, in a parallel study, found that compound 5 activates STAT3, which promotes transcription of the CAMP gene by increasing the expression of HIF-1α23. This seems to be one major mechanism for regulation of gene expression of LL-37, although there may also be other mechanisms involved.…”

“…We have revealed some correlations between structure and activity, but further variation of the structure is needed in order to optimize activity vs toxicity. Mechanistic studies23 and evaluation of possible side-effects should be performed in the process of selecting which compounds are most suitable for future clinical trials. It is, however, clear that there is a high potential to utilize APDs in the treatment of infections by induction of endogenous antimicrobial peptides.…”

Treatment with Entinostat Heals Experimental Cholera by Affecting Physical and Chemical Barrier Functions of Intestinal Epithelia

“…Other mechanisms are likely to be responsible for the efficient induction of LL-37 by APDs. One major route seems to be activation of STAT3, which, in turn, induces HIF-1; HIF-1 subsequently increases the expression of LL-37 and HBD-1 (29).…”

Hif-1α Overexpression Improves Transplanted Bone Mesenchymal Stem Cells Survival in Rat MCAO Stroke Model

“…Hypoxia-inducible factor 1 (Hif-1) is a master regulator of the cellular response to hypoxia, which is a dimer consisting of the inducible Hif-1α subunit and the constitutively expressed Hif-1β subunit (Miraglia et al, 2016). Under aerobic conditions, Hif-1α remains inactive, while its activation is often associated with the function of Hif-1 transcription factor (Badowska-Kozakiewicz et al, 2016).…”