A novel STAT3 CCD inhibitor for suppressing macrophage activation and lipopolysaccharide-induced acute lung injury

Signal transducer and activator of transcription 3 (STAT3) has a crucial role in inflammation in lipopolysaccharide (LPS)-induced acute lung injury (ALI). The current study aimed at developing a novel STAT3 coiled-coil domain (CCD) inhibitor for suppression of inflammatory response in LPS-induced ALI.

Molecular docking and binding affinity were proceeded and determined that K134 bond to STAT3 CCD. Then K134 [(E)-N'-(1-(2,4-dihydroxyphenyl)ethylidene)-2-(o-tolyloxy)acetohydrazide] was applied to RAW264.7 macrophages for further ex vivo investigation of possible mechanism. The intratracheal injection of LPS-induced ALI model of C57BL/6j mice was established for evaluating therapeutic effect of K134 on ALI and inflammation in vivo. iNOS and pro-inflammatory cytokines, including TNF-α, IL-1β and IL-6, in BALF of LPS-induced ALI were also determined.

Molecular docking results disclosed that Asn175 and Gln202 were involved in K134 binding to STAT3 CCD and its binding affinity was at 4.68 μM. Moreover, further tests showed that K134 blunted activation and the subsequent STAT3 phosphorylation in LPS-treated macrophages. Also, K134 (30 mg/kg) alleviated LPS-induced lung injury and blocked STAT3 phosphorylation in lung. Further, K134 decreased iNOS, pro-inflammatory cytokines, inflammatory cell infiltration and NO production of LPS-induced ALI. Preliminary safety evaluation indicated that K134 had a favorable safety profile at the dose of 30 mg/kg.

We identified a novel inhibitor of STAT3 CCD, K134, which markedly attenuated LPS-induced ALI inflammation by targeting STAT3 phosphorylation. This supports a possible future use of K134 in treating inflammatory diseases involving activation of STAT3-mediated pathways.