Malaria is a Plasmodium falciparum-caused febrile blood borne disease that drives excessive production of proinflammatory cytokines and promotes the development of severe malaria symptoms. To understand this excessive cytokine production, the epigenetic and transcriptional pathways regulating cytokine production is investigated, as this may reveal novel therapeutic targets to treat malaria.
In this study, the transcriptional NF-kB-JMJD3 pathway is investigated in the production of cytokines TNF, IL-1β, IL-6 and IL-10; as well as elucidating malaria-induced histone modifications in monocytes. Naïve monocytes were treated with lysed P.falciparum-infected red blood cells (iRBC) for up to 4 hours. Cytokine gene and protein expression were measured by qPCR and ELISA, respectively, while the activity of transcription factors (e.g. NF-kB phosphorylation) and histone modifications (e.g. histone 3 lysine 27 trimethylation (H3K27me3)) were determined by Western blotting. Enriched histone extracts from iRBC-treated monocytes were screened using a Histone 3 modification multiplex assay to detect differently regulated histone modifications.
Results showed that iRBC-treated monocytes produced elevated cytokine levels, but without altering NF-kB phosphorylation or H3K27me3 levels. However, 2-fold and 1.2-fold increases in novel H3K4me1 and H3K4me3 modifications, respectively, were identified in iRBC-treated monocytes through the multiplex histone 3 assay. Pharmacological inhibition of H3K4-methyltransferase activity with WDR5-0103 did not affect global H3K4 methylation levels, but significantly reduced secreted levels of TNF and IL-6 y iRBC-treated monocytes.
In conclusion, these results collectively indicate that malaria-induced cytokine production in monocytes is not regulated through the NF-kB-JMJD3 pathway, rather through the H3K4 modifications. Further investigation into the location of the H3K4me1 and H3K4me3 modifications along the TNF and IL-6 gene locus is warranted. This may further support a case for targeting such modifications as potential anti-malarial therapeutics.