Background Brain injury is the main cause of high mortality and disability after successful cardiopulmonary resuscitation (CPR) from sudden cardiac arrest (CA). The transient receptor potential M4 (TRPM4) channel is a novel target for ameliorating blood–brain barrier (BBB) disruption and neuroinflammation. Herein, we tested whether flufenamic acid (FFA), which is reported to block TRPM4 with high potency, could confer neuroprotection against brain injury secondary to CA/CPR and whether its action was exerted by blocking the TRPM4 channel. Methods Wild-type (WT) and Trpm4 knockout (Trpm4−/−) mice subjected to 10-min CA/CPR were randomized to receive FFA or vehicle once daily. Post-CA/CPR brain injuries including neurologic deficits, survival rate, histological damage, edema formation, BBB destabilization and neuroinflammation were assessed. Results In WT mice subjected to CA/CPR, FFA was effective in improving survival and neurologic outcome, reducing neuropathological injuries, attenuating brain edema, lessening the leakage of IgG and Evans blue dye, restoring tight junction protein expression and promoting microglia/macrophages from the pro-inflammatory subtype toward the anti-inflammatory subtype. In comparison to WT mice, Trpm4−/− mice exhibited less neurologic deficiency, milder histological impairment, more BBB integrity and more anti-inflammatory microglia/macrophage polarization. As expected, FFA did not provide a benefit of superposition compared with vehicle in the Trpm4−/− mice after CA/CPR. Conclusions FFA mitigates BBB breach and modifies the functional status of microglia/macrophages, thereby improving survival and neurologic deficits following CA/CPR. The neuroprotective effects occur at least partially by interfering with the TRPM4 channel in the neurovascular unit. These results indicate the significant clinical potential of FFA to improve the prognosis for CA victims who are successfully resuscitated.

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Neuroinflammation plays a key role in the pathogenesis of post-cardiac arrest (CA) brain injury. Innate immune cells sense a variety of danger signals through pattern-recognition receptors and evoke rapidly after ischemic challenge, triggering inflammatory responses and amplifying brain damage. A programmed cell death (PCD) pathway is activated after ischemic and/or inflammatory stimuli, leading to the elimination of the damaged cells. However, PCD also regulates inflammatory responses flexibly. The present review aimed to summarize the mechanisms of inflammatory responses, including the biology of immune cells, the innate immune recognition that initiates the inflammation, and the immunomodulatory effects of PCD following CA. Promising therapeutic approaches of targeting inflammatory responses to alleviate brain injury and improve neurological outcomes after CA are also reviewed.