Exploring Candesartan, an angiotensin II receptor antagonist, as a novel inhibitor of NLRP3 inflammasome: alleviating inflammation in Neisseria gonorrhoeae infection.

Background: Gonorrhea, induced by Neisseria gonorrhoeae infection, stands as a prevalent sexually transmitted inflammatory disease globally. Our earlier research illuminated that N. gonorrhoeae-infected macrophages provoke inflammation by activating the intracellular sensor NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasome, a pivotal regulator in inflammatory diseases governing the maturation and secretion of interleukin (IL)-1β and IL-18. Nevertheless, effective therapies addressing N. gonorrhoeae-mediated NLRP3 inflammasome activation and ensuing inflammation are currently lacking. This study delves into the impact of the angiotensin II receptor antagonist Candesartan (CS) on N. gonorrhoeae-infected macrophages.

Methods: The protein expression levels were examined through ELISA and Western blotting. Intracellular H₂O₂ levels, mitochondrial reactive oxygen species, and mitochondrial membrane integrity were evaluated using targeted fluorescent probes and analyzed via flow cytometry. NF-κB transcriptional activity was assessed using NF-κB reporter cells. LC3-knockdown cells were created using CRISPR/Cas9 technology.

Results: CS effectively inhibits the NLRP3 inflammasome, as indicated by the suppression of caspase-1 activation, IL-1β secretion, NLRP3 release, and the release of apoptosis-associated speck-like protein containing a CARD (ASC) in N. gonorrhoeae-infected J774A.1 macrophages. Additionally, CS selectively impedes IL-6 secretion and iNOS expression in both N. gonorrhoeae-infected J774A.1 and RAW264.7 macrophages. Mechanistic insights uncover the inhibition of NF-κB by CS in N. gonorrhoeae-infected J774A.1 macrophages, while intracellular H₂O₂ generation, mitogen-activated protein kinases phosphorylation, and mitochondrial damage remain unaffected. Notably, our study highlights that CS-induced autophagy contributes partially to its inhibitory effect on the NLRP3 inflammasome.

Conclusions: These results underscore the potential of CS as an anti-inflammatory drug for the treatment of gonorrhea, addressing a critical unmet medical need in combating N. gonorrhoeae-induced inflammation.