Homo- or heterodimeric compounds that affect dimeric protein function through interaction between monomeric moieties and protein subunits can serve as valuable sources of potent and selective drug candidates. Here, we screened an in-house dimeric natural product collection, and panepocyclinol A (PecA) emerged as a selective and potent STAT3 inhibitor with profound anti-tumor efficacy. Through cross-linking C712/C718 residues in separate STAT3 monomers with two distinct Michael receptors, PecA inhibits STAT3 DNA binding affinity and transcription activity. Molecular dynamics simulation reveals the key conformation changes of STAT3 dimers upon the di-covalent binding with PecA that abolishes its DNA interactions. Furthermore, PecA exhibits high efficacy against anaplastic large T cell lymphoma in vitro and in vivo, especially those with constitutively activated STAT3 or STAT3^Y640F. In summary, our study describes a distinct and effective di-covalent modification for the dimeric compound PecA to disrupt STAT3 function.

OBJECTIVE: To investigate the changes in the expression of voltage-gated potassium channel subunit KCNA2 in the dorsal root ganglion (DRG) neurons of rats with osteoarthritis (OA) pain induced by sodium monoiodoacetate and explore the mechanism. METHODS: A total of 156 adult male Sprague-Dawley rats were randomly divided into blank control group, saline group and intra-articular monoiodoacetate injection-induced OA group. The paw withdrawal mechanical threshold (PWMT) was measured before and at 1, 2, 4, and 6 weeks after monoiodoacetate injection. At 4 weeks after the injection, the pathological changes in the knee joints were analyzed using HE staining and Safranin O-Fast Green staining, and the expression of activating transcription factor 3 (ATF-3) and inducible nitric oxide synthase (iNOS) in the DRG neurons were detected by immunofluorescence staining. The expression of mRNA in the DRG neurons was detected by RT-qPCR at 1, 2, 4 and 6 weeks after the injection. The expression of KCNA2 in the DRG was measured by Western blotting, and the methylation level of promoter region was measured by MSPCR at 4 weeks after the injection. RESULTS: The PWMT of the rats in OA group was significantly decreased at 2, 4, and 6 weeks after the injection as compared with the baseline ( < 0.05 or < 0.001) as well as the control group ( < 0.05 or < 0.001). Four weeks after the intra-articular injection, fractures and defects on the surface of the articular cartilage, bone hyperplasia, and blurred tidal line were observed in the rats in OA group, but no obvious pathological changes were detected in the control or saline groups. Compared with those in the control group, the expressions of ATF-3 and iNOS were significantly increased ( < 0.01) at 4 weeks after injection; the expression of mRNA at 2, 4 and 6 weeks and the expression of KCNA2 protein at 4 weeks were all significantly decreased ( < 0.05 or < 0.01), and the methylation level of gene was significantly increased at 4 weeks after the injection in OA group ( < 0.01). CONCLUSIONS The expression of KCNA2 is decreased in the DRG neurons of rats with OA pain likely as a result of enhanced methylation of promoter region.
Animals ; Disease Models, Animal ; Ganglia, Spinal ; Knee Joint ; Kv1.2 Potassium Channel ; metabolism ; Male ; Osteoarthritis ; complications ; metabolism ; Pain ; etiology ; metabolism ; Promoter Regions, Genetic ; Rats ; Rats, Sprague-Dawley

Objective To evaluate the role of different opioid receptors in morphine postconditioning-induced reduction of ischemia-reperfusion (Ⅰ/R) injury in isolated rat hearts.Methods Healthy adult male Sprague-Dawley rats,aged 7-8 weeks,weighing 250-300 g,were anesthetized with chloral hydrate.The hearts were removed and retrogradely perfused with oxygenated K-H solution in a Langendorff apparatus.Forty-eight Langendorff-perfused rat hearts were divided into 4 groups (n=12 each) by a random number table method:Ⅰ/R group,morphine postconditioning group (M group),δ receptor antagonist naltrexone plus morphine postconditioning group (N+M group) and κ receptor antagonist nor-binaltorphimine plus morphine postconditioning group (B+M group).Hearts were subjected to 4 cycles of perfusion with K-H solution containing 1 μmol/L morphine for 15 s and then with K-H solution containing no morphine for 15 s in group M.In N+M group and B+M group,hearts were perfused with 5 μmol/L naltrindole and 5 μmol/L nor-binaltorphimine,respectively,starting from 10 nin of equilibration until 5 min of reperfusion,and morphine postconditioning was similar to those previously described in group M.Heart rate and the maximum rate of increase or decrease in left ventricular pressure (±dp/dtmax) were recorded at 20 min of equilibration and 30 and 60 nin of reperfusion.Corona~ effluent was collected at 20 min of equilibration and 60 min of reperfusion for measurement of the activity of creatine kinase by colorimetric assay.Eight hearts were obtained at 60 min of reperfusion for determination of myocardial infarct size.Four hearts were obtained at 60 min of reperfusion for detection of the expression of microtubule-associated protein 1 light chain 3 Ⅰ (LC3 Ⅰ) and LC3 Ⅱ by Western blot.LC3 Ⅱ/LC3 Ⅰ ratio was calculated.Results Compared with the baseline value at 20 min of equilibration,heart rate and +dp/dt were significantly decreased at 30 and 60 min of reperfusion,and the activity of creatine kinase in coronary effluent was increased at 60 min of reperfusion in four groups (P＜0.05).Compared with group Ⅰ/R,the activity of creatine kinase in coronary effluent,percentage of myocardial infarct size and LC3 Ⅱ/LC3 Ⅰ ratio were significantly decreased in group M (P＜0.05).Compared with group M,the activity of creatine kinase in coronary effluent,percentage of myocardial infarct size and LC3 Ⅱ/LC3 Ⅰ ratio were significantly increased in N+M and B+M groups (P＜0.05).Conclusion δ and κ opioid receptors are involved in morphine postconditioning-induced reduction of Ⅰ/R injury in isolated rat hearts,and the mechanism may be related to inhibiting the level of autophagy.