Background: Ensuring the survival of the distal end of a random flap during hypoperfusion (ischaemia) is difficult in clinical practice. Effective prevention of programmed cell death is a potential strategy for inhibiting ischaemic flap necrosis. The activation of stimulator of interferon genes (STING) pathway promotes inflammation and leads to cell death. The epidermal growth factor family member neuregulin-1 (NRG1) reduces cell death by activating the protein kinase B (AKT) signalling pathway. Moreover, AKT signalling negatively regulates STING activity. We aimed to verify the efficacy of NRG1 injection in protecting against flap necrosis. Additionally, we investigated whether NRG1 effectively enhances ischemic flap survival by inhibiting pyroptosis and necroptosis through STING suppression. Methods: A random-pattern skin flap model was generated on the backs of C57BL/6 mice. The skin flap survival area was determined. The blood supply and vascular network of the flap was assessed by laser Doppler blood flow analysis. Cluster of differentiation 34 immunohistochemistry (IHC) and haematoxylin and eosin (H&E) staining of the flap sections revealed microvessels. Transcriptome sequencing analysis revealed the mechanism by which NRG1 promotes the survival of ischaemic flaps. The levels of angiogenesis, oxidative stress, necroptosis, pyroptosis and indicators associated with signalling pathways in flaps were examined by IHC, immunofluorescence and Western blotting. Packaging adeno-associated virus (AAV) was used to activate STING in flaps. Results: NRG1 promoted the survival of ischaemic flaps. An increased subcutaneous vascular network and neovascularization were found in ischaemic flaps after the application of NRG1. Transcriptomic gene ontology enrichment analysis and protein level detection indicated that necroptosis, pyroptosis and STING activity were reduced in the NRG1 group. The phosphorylation of AKT and forkhead box O3a (FOXO3a) were increased after NRG1 treatment. The increased expression of STING in flaps induced by AAV reversed the therapeutic effect of NRG1. The ability of NRG1 to phosphorylate AKT-FOXO3a, inhibit STING and promote flap survival was abolished after the application of the AKT inhibitor MK2206. Conclusions: NRG1 inhibits pyroptosis and necroptosis by activating the AKT-FOXO3a signalling pathway to suppress STING activation and promote ischaemic flap survival.

Curcumin, a natural product, has been shown to possess notable anti-inflammatory activities and numerous studies have been carried out on its clinical applications. Recently, several reports mentioned that myeloid differentiation protein 2 (MD-2) may be the direct target of curcumin in the inhibition of lipopolysaccharide (LPS) signaling. However, the exact interaction between curcumin and MD-2 is still incompletely understood. In the present study, computational and experimental methods were employed to explore the underlying structural mechanism of curcumin binding to the MD-2 protein. Molecular docking and molecular dynamics (MD) simulation studies showed that curcumin could be embedded into the hydrophobic pocket of MD-2 and form stable hydrogen bonding interactions with residues R90 and Y102 of MD-2. Moreover, experimental results of curcumin binding to the MD-2^R90A/Y102A mutant further confirmed that residues ARG-90 and TYR-102 contribute to the recognition process of curcumin binding to the MD-2 protein. In conclusion, we have explored the binding mechanism of curcumin to MD-2; more importantly, this work could offer useful references for designing novel analogs of curcumin as potential anti-inflammatory agents targeting the MD-2 protein.

Myeloid differentiation factor 88 (MyD88) is a hub protein in the Toll-like receptor signaling pathway, which acts as a master switch for numerous inflammatory diseases, including acute lung injury (ALI). Although this protein is considered as a crucial therapeutic target, there are currently no clinically approved MyD88-targeting drugs. Based on previous literature, here we report the discovery via computer-aided drug design (CADD) of a small molecule, M20, which functions as a novel MyD88 inhibitor to efficiently relieve lipopolysaccharide-induced inflammation both in vitro and in vivo. Computational chemistry, surface plasmon resonance detection (SPR) and biological experiments demonstrated that M20 forms an important interaction with the MyD88-Toll/interleukin-1 receptor domain and thereby inhibits the protein dimerization. Taken together, this study found a MyD88 inhibitor, M20, with a novel skeleton, which provides a crucial understanding in the development and modification of MyD88 inhibitors. Meanwhile, the favorable bioactivity of the hit compound is also conducive to the treatment of acute lung injury or other more inflammatory diseases.

Background: Ischemic necrosis frequently affects the distal portion of skin flaps, particularly in diabetic patients. PANoptosis, a form of inflammatory programmed cell death, is implicated in vascular damage. This study examined whether 3,4-dimethoxychalcone (3,4-DC), a novel caloric restriction (CR) mimetic, could inhibit PANoptosis and promote the survival of ischemic and diabetic flaps. Methods: Flap viability was evaluated using laser Doppler blood flow imaging and histological analysis. Western blotting and immunofluorescence were used to assess PANoptosis and autophagy. Quantitative PCR was used to measure microRNA levels. Caspase-1 knockout and db/db mice were used to explore the effects of 3,4-DC on pyroptosis and diabetic complications. Results: 3,4-DC significantly improved ischemic flap survival and enhanced tissue perfusion. PANoptosis was inhibited, and autophagy was activated following 3,4-DC treatment, whereas these effects were abolished by the autophagy inhibitor chloroquine. Transcription factor EB (TFEB) inhibition reduced autophagy and reversed the protective effects of 3,4-DC. miR-107-3p was identified as a 3,4-DC-responsive microRNA that modulates TFEB nuclear translocation through the miR-107-3p/Wnt3a/mTOR pathway. Similar therapeutic effects were observed in diabetic flaps. Conclusion: 3,4-DC promotes the survival of ischemic and diabetic skin flaps by activating autophagy and inhibiting PANoptosis through the miR-107-3p/Wnt3a/mTOR/TFEB axis.