Pyruvate kinase M2 mediates IL-17 signaling in keratinocytes driving psoriatic skin inflammation.

Psoriasis is an inflammatory skin disease characterized by keratinocyte proliferation and inflammatory cell infiltration induced by IL-17. However, the molecular mechanism through which IL-17 signaling in keratinocytes triggers skin inflammation remains not fully understood. Pyruvate kinase M2 (PKM2), a glycolytic enzyme, has been shown to have non-metabolic functions. Here, we report that PKM2 mediates IL-17A signaling in keratinocytes triggering skin psoriatic inflammation. We find high expression of PKM2 in the epidermis of psoriatic patients and mice undergoing psoriasis models. Specific depletion of PKM2 in keratinocytes attenuates the development of experimental psoriasis by reducing the production of pro-inflammatory mediators. Mechanistically, PKM2 forms a complex with Act1 and TRAF6 regulating NF-κB transcriptional signaling downstream of the IL-17 receptor. As IL-17 also induces PKM2 expression in keratinocytes, our findings reveal a sustained signaling circuit critical for the psoriasis-driving effects of IL-17A, suggesting that PKM2 is a potential therapeutic target for psoriasis.

Gasdermin D inhibition prevents multiple organ dysfunction during sepsis by blocking NET formation.

Multiple organ dysfunction is the most severe outcome of sepsis progression and is highly correlated with a worse prognosis. Excessive neutrophil extracellular traps (NETs) are critical players in the development of organ failure during sepsis. Therefore, interventions targeting NET release would likely effectively prevent NET-based organ injury associated with this disease. Herein, we demonstrate that the pore-forming protein gasdermin D (GSDMD) is active in neutrophils from septic humans and mice and plays a crucial role in NET release. Inhibition of GSDMD with disulfiram or genic deletion abrogated NET formation, reducing multiple organ dysfunction and sepsis lethality. Mechanistically, we demonstrate that during sepsis, activation of the caspase-11/GSDMD pathway controls NET release by neutrophils during sepsis. In summary, our findings uncover a novel therapeutic use for disulfiram and suggest that GSDMD is a therapeutic target to improve sepsis treatment.

Frontline Science: Blood-circulating leukocytes fail to infiltrate the spinal cord parenchyma after spared nerve injury.

The development of neuropathic pain after peripheral nerve injury involves neuroimmune-glial interactions in the spinal cord. However, whether the development of neuropathic pain depends on the infiltration of peripheral immune cells, such as monocytes, into the spinal cord parenchyma after peripheral nerve damage remains unclear. Here, we used a combination of different techniques such as transgenic reporter mouse (Cx3cr1GFP/+ and Ccr2RFP/+ mice), bone marrow chimeric mice, and parabiosis to investigate this issue in spared nerve injury (SNI) model. Herein, we provided robust evidence that, although microglial cells are activated/proliferate at the dorsal horn of the spinal cord after SNI, peripheral hematopoietic cells (including monocytes) are not able to infiltrate into the spinal cord parenchyma. Furthermore, there was no evidence of CCR2 expression in intrinsic cells of the spinal cord. However, microglial cells activation/proliferation in the spinal cord and mechanical allodynia after SNI were reduced in Ccr2-deficient mice. These results suggest that blood-circulating leukocytes cells are not able to infiltrate the spinal cord parenchyma after distal peripheral nerve injury. Nevertheless, they indicate that CCR2-expressing cells might be indirectly regulating microglia activation/proliferation in the spinal cord after SNI. In conclusion, our study supports that CCR2 inhibition could be explored as an interventional approach to reduce microglia activation and consequently neuropathic pain development after peripheral nerve injury.