Exp Ther Med. 2021 Oct;22(4):1081. doi: 10.3892/etm.2021.10515. Epub 2021 Jul 29.
ABSTRACT
Herbal melanin (HM), extracted from Nigella sativa, is known for its immunogenic properties through the modulation of cytokine production via Toll-like receptor (TLR)4. TLRs play a crucial role in the host defense through the regulation of innate and adaptive immune responses. However, the potential effect of HM on the production of interleukin-1β (IL-1β), the main immunoregulatory cytokine secreted by activated monocytes, has not been reported. The present study aimed to investigate the effects of HM on IL-1β secretion and production, detected by enzyme-linked immunosorbent assay, western blotting and mRNA expression monitored by reverse transcription-PCR, in human monocytes and a monocytic cell line, THP-1. Signaling pathways involved in the HM-induced IL-1β production was investigated in the THP-1 cells. It was shown that HM upregul ated the IL-1β mRNA in the THP-1 cells and induced the secretion of IL-1β in the monocytes and THP-1 cells, in a dose-dependent manner, compared to the untreated cells. HM increased the protein expression of IL-1β, TLR2, the main receptor for IL-1β production, and activated p38 mitogen-activated protein kinase (MAPK), a key mediator for stress-induced IL-1β gene expression. The blockade of the p38 MAPK pathway, with the pharmacological inhibitor SB202190, and TLR2 receptor with a neutralization antibody, resulted in the decrease of HM-induced IL-1β production in THP-1 cells. The TLR4 receptor blockade also decreased HM-induced IL-1β production, but to a lesser extent than TLR2 blockade. In conclusion, the present study demonstrated that HM stimulates IL-1β production in monocytes and THP-1 cells, in a TLR2/p38 MAPK pathway-dependent manner, suggesting promising immunoregulatory potentials of HM against inflammatory-associated diseases.
PMID:34447474 | PMC:PMC8355711 | DOI:10.3892/etm.2021.10515
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