Epigenetic silencing of selected hypothalamic neuropeptides in narcolepsy with cataplexy.

Narcolepsy with cataplexy is a sleep disorder caused by deficiency in the hypothalamic neuropeptide hypocretin/orexin (HCRT), unanimously believed to result from autoimmune destruction of hypocretin-producing neurons. HCRT deficiency can also occur in secondary forms of narcolepsy and be only temporary, suggesting it can occur without irreversible neuronal loss. The recent discovery that narcolepsy patients also show loss of hypothalamic (corticotropin-releasing hormone) CRH-producing neurons suggests that other mechanisms than cell-specific autoimmune attack, are involved. Here, we identify the HCRT cell-colocalized neuropeptide QRFP as the best marker of HCRT neurons. We show that if HCRT neurons are ablated in mice, in addition to Hcrt, Qrfp transcript is also lost in the lateral hypothalamus, while in mice where only the Hcrt gene is inactivated Qrfp is unchanged. Similarly, postmortem hypothalamic tissues of narcolepsy patients show preserved QRFP expression, suggesting the neurons are present but fail to actively produce HCRT. We show that the promoter of the HCRT gene of patients exhibits hypermethylation at a methylation-sensitive and evolutionary-conserved PAX5:ETS1 transcription factor-binding site, suggesting the gene is subject to transcriptional silencing. We show also that in addition to HCRT, CRH and Dynorphin (PDYN) gene promoters, exhibit hypermethylation in the hypothalamus of patients. Altogether, we propose that HCRT, PDYN, and CRH are epigenetically silenced by a hypothalamic assault (inflammation) in narcolepsy patients, without concurrent cell death. Since methylation is reversible, our findings open the prospect of reversing or curing narcolepsy.

Human TH17 cells engage gasdermin E pores to release IL-1α on NLRP3 inflammasome activation.

It has been shown that innate immune responses can adopt adaptive properties such as memory. Whether T cells utilize innate immune signaling pathways to diversify their repertoire of effector functions is unknown. Gasdermin E (GSDME) is a membrane pore-forming molecule that has been shown to execute pyroptotic cell death and thus to serve as a potential cancer checkpoint. In the present study, we show that human T cells express GSDME and, surprisingly, that this expression is associated with durable viability and repurposed for the release of the alarmin interleukin (IL)-1α. This property was restricted to a subset of human helper type 17 T cells with specificity for Candida albicans and regulated by a T cell-intrinsic NLRP3 inflammasome, and its engagement of a proteolytic cascade of successive caspase-8, caspase-3 and GSDME cleavage after T cell receptor stimulation and calcium-licensed calpain maturation of the pro-IL-1α form. Our results indicate that GSDME pore formation in T cells is a mechanism of unconventional cytokine release. This finding diversifies our understanding of the functional repertoire and mechanistic equipment of T cells and has implications for antifungal immunity.