Effect of a Histone Deacetylases Inhibitor of IL-18 and TNF-Alpha Secretion in Vitro

BACKGROUND: Interleukin-18 (IL-18) and Tumor Necrosis Factor-alpha (TNF-α) are proinflammatory cytokines that increased the development of Th1 immune response, but have a different type of regulation of the gene expression. Whereas TNF-α has an inducible expression, IL-18 is translated as an inactive protein and required proteolytic cleavage by Casp-1 in inflammasome complexes.AIM: To investigate the effect of the histone deacetylases inhibitor Suberoylanilide Hydroxamic Acid (SAHA) on the gene expression and secretion of both cytokines, IL-18 and TNF-α, according to their contribution to the cancer development and anticancer immunity.METHODS: Isolated peripheral blood mononuclear cells (PBMC) were stimulated with LPS and C3bgp with or without SAHA. Cytokine production was assessed by ELISA at 6 and 24h.RESULTS: IL-18 and TNF-α secretion was significantly increased at 6h and 24h in response to stimulation. TNF-α production from stimulated PBMC was downregulated by SAHA at 6 and 24h. Treatment with SAHA does not inhibit the secretion of IL-18 significantly either at 6 or 24h of stimulation.CONCLUSION: The inhibition of histone deacetylases by SAHA does not influence the inflammasome-dependent production of immunologically active IL-18. In contrast, the production of proinflammatory TNF-α in cultures was mediated by the activity of HDAC class I and class II enzymes

EFFECT OF SAHA AND C-JUN N-TERMINAL KINASE INHIBITOR ON THE INDUCIBLE MRNA EXPRESSION OF INTERLEUKIN-17

Interleukin-17 (IL-17A) is a critical cytokine for immune defence against extracellular bacterial and fungal infections. Excess production during chronic inflammation has been associated with many inflammatory and autoimmune disorders. On the other hand, the inducible expression of many cytokine genes is regulated by the receptor-activated intracellular signaling pathways, including the JNK pathway, and different epigenetic mechanisms, including histone deacetylation by HDACs. We investigated the comparative effect of the HDACs inhibitor Suberoylanilide Hydroxamic Acid (SAHA) and an inhibitor of the JNK signaling pathway in the regulation of the inducible IL-17 expression at the mRNA level in PBMCs from healthy donors. For the detection of IL-17 mRNA transcripts was used qRT-PCR. We detected significantly increased levels of IL-17mRNA under the stimulation of the PBMC cultures with lipopolysaccharide (LPS) or C3 binding glycoprotein (C3bgp) in the presence of an inhibitor of the JNK transduction pathway. The inhibition of the JNK signaling pathway leads to the upregulation of the expression of IL-17mRNA. SAHA did not demonstrate a significant effect on the IL-17mRNA transcription compared to the inhibitor of the JNK pathway. In conclusion, we suppose that the synthesis of IL-17 mRNA is regulated by both the JNK transduction pathway and HDAC activity, but with different effects

Effect of a Small Selective Inhibitor of C-Jun N-Terminal Kinase on the Inducible mRNA Expression of Interleukin-6 and Interleukin-18

BACKGROUND: The expression of many inducible genes, involved in cell growth and differentiation as cytokine genes are regulated by receptor-activated intracellular signalling pathways, including the c-Jun N-terminal kinase (JNK) mitogen-activated protein kinase pathway. AIM: We examined the involvement of the JNK signalling pathway in the regulation of the inducible interleukin-6 (IL-6) and interleukin-18 (IL-18) gene expression at the transcriptional level. METHODS: Peripheral blood mononuclear cells (PBMC) from healthy donors were stimulated with lipopolysaccharide (LPS) and C3 binding glycoprotein (C3bgp) with or without SP600125 and cultured for 6 h. After mRNA isolation, a qRT-PCR was performed. RESULTS: Regarding IL-6 and IL-18 mRNA expression, donors were divided into two groups of high and low responders. SP600125 inhibited significantly IL-6 mRNA transcription in the high responder group and did not influence the transcription level in the low responder group. Concerning IL-18 mRNA, we detect the significant effect of SP600125 on the inducible mRNA in high responder group upon C3bgp stimulation. CONCLUSION: JNK transduction pathway is involved in the production of IL-6 mRNA, after LPS and C3bgp stimulation. We suggest that the inhibition of JNK may be beneficial only for higher responding patients during the treatment of inflammatory and autoimmune diseases