STAT3 serine phosphorylation is required for TLR4 metabolic reprogramming and IL-1ß expression.

Detection of microbial components such as lipopolysaccharide (LPS) by Toll-like receptor 4 (TLR4) on macrophages induces a robust pro-inflammatory response that is dependent on metabolic reprogramming. These innate metabolic changes have been compared to aerobic glycolysis in tumour cells. However, the mechanisms by which TLR4 activation leads to mitochondrial and glycolytic reprogramming are unknown. Here we show that TLR4 activation induces a signalling cascade recruiting TRAF6 and TBK-1, while TBK-1 phosphorylates STAT3 on S727. Using a genetically engineered mouse model incapable of undergoing STAT3 Ser727 phosphorylation, we show ex vivo and in vivo that STAT3 Ser727 phosphorylation is critical for LPS-induced glycolytic reprogramming, production of the central immune response metabolite succinate and inflammatory cytokine production in a model of LPS-induced inflammation. Our study identifies non-canonical STAT3 activation as the crucial signalling intermediary for TLR4-induced glycolysis, macrophage metabolic reprogramming and inflammation.

Repurposing drugs targeting the P2X7 receptor to limit hyperinflammation and disease during influenza virus infection.

BACKGROUND AND PURPOSE: Severe influenza A virus (IAV) infections are associated with damaging hyperinflammation that can be fatal. There is an urgent need to identify new therapeutic agents to treat severe and pathogenic IAV infections. Repurposing of drugs with an existing and studied pharmacokinetic and safety profile is a highly attractive potential strategy. We have previously demonstrated that the NLRP3 inflammasome plays time-dependent roles during severe IAV infection with early protective responses and later dysregulation leading to excessive inflammation, contributing to disease severity. EXPERIMENTAL APPROACH: We tested two existing drugs, probenecid and AZ11645373, to target P2X7 receptor signalling and dampen NLRP3 inflammasome responses during severe IAV infection. In vitro, the drugs were assessed for their ability to limit NLRP3 inflammasome-dependent IL-1ß secretion in macrophage cultures. In vivo, their effects were assessed on hyperinflammation and disease during severe IAV infection in C57BL/6 mice. KEY RESULTS: Treatment of macrophages with probenecid or AZ11645373 in vitro diminished NLRP3 inflammasome-dependent IL-1ß secretion. Intranasal therapeutic treatment of mice displaying severe influenza disease with probenecid or AZ11645373 reduced pro-inflammatory cytokine production, cellular infiltrates in the lung, and provided protection against disease. Importantly, these drugs could be administered at either early or late stage of disease and provide therapeutic efficacy. CONCLUSIONS AND IMPLICATIONS: Our study demonstrates that the anti-inflammatory drugs probenecid and AZ11645373, which have documented pharmacokinetics and safety profiles in humans, are effective at dampening hyperinflammation and severe influenza disease providing potentially new therapeutic strategies for treating severe or pathogenic IAV infections.

Type-I interferons mediate the neuroinflammatory response and neurotoxicity induced by rotenone.

Evidence from post-mortem human brains, animal studies and cell culture models has implicated neuroinflammation in the aetiology of chronic neuropathologies including Alzheimer's and Parkinson's diseases. Although the neuroinflammatory response is considered detrimental in contributing to these pathologies, the underlying mechanisms are still not well understood. The type-I interferons (IFNs) have been well characterised in the periphery and are known to initiate/modulate the immune response. Recently, they have been implicated in ageing and we have also demonstrated increased type-I IFN expression in post-mortem human Alzheimer's and Parkinson's disease brains. We hypothesise that the type-I IFNs are key drivers of the damaging, self-perpetuating pro-inflammatory response that contributes to these chronic neuropathologies. In support of this, we have recently confirmed in models of Alzheimer's and Parkinson's disease that mice lacking the type-I IFN receptor (IFNAR1), display an attenuated neuroinflammatory response with subsequent neuroprotection. To further investigate type-I IFN-mediated neuroinflammation and the specific CNS cell types involved, this study treated primary cultured wild-type and IFNAR1-/- neurons or mixed glia with the mitochondrial complex I inhibitor, rotenone. Wild-type neurons and glia treated with 3 nM and 25 nM rotenone, respectively, exhibited a pro-inflammatory response, including increased type-I IFN expression that was attenuated in cells lacking IFNAR1. Reduced type-I IFN signalling in IFNAR1-/- neurons also conferred protection against caspase-3-mediated rotenone-induced cell death. Further, this reduced pro-inflammatory response in the IFNAR1-/- glia subsequently diminished their neurotoxic effects to wild-type neurons. In support of this, we confirmed that therapeutically targeting the type-I IFN glial response to rotenone through a specific IFNAR1 blocking monoclonal antibody was neuroprotective. Our data has confirmed that both neurons and glia contribute to the pro-inflammatory response induced by rotenone with attenuation of this response beneficial in reducing neuronal cell death. Read the Editorial Comment for this article on page 9.