Bioactive Small Molecule Enhances Skin Burn Wound Healing and Hair Follicle Regeneration by Activating PI3K/AKT Signaling Pathway: A Preclinical Evaluation in Animal Model.

Rational: A bioactive small molecule of precision medicine involves targeted therapies. Shikonin, a herbal extract, is an active small molecule that is traditionally used in wound healing for its anti-tumor and anti-inflammatory properties. Therefore, the present study aims to evaluate the anti-inflammatory role of shikonin in skin burn wound healing and hair follicle regeneration and to identify molecular signaling pathways that promote the regeneration. Method: A secondary skin burn model of mice was established by conventional method. The burn wound was externally treated with shikonin ointment and excipient treated mice were used as controls. Skin samples were taken on the day 3 and 7 after drug treatment and the dosage was unified in the experiments. The wound healing process was observed by histopathological and immunofluorescence (IF) staining. The proliferation of hair follicle cells in wound skin was tracked by 5-Ethynyl-2'-deoxyuridne (EdU) staining. The inflammatory factors at the wound healing site were quantified by polymerase chain reaction (qPCR). The PI3K/Akt, P65, Ki67 signaling proteins and Bax/BCL2 apoptosis proteins were studied by western blot analysis. The functionality of PI3K/Akt signaling pathway was tested using LY294002, an inhibitor of PI3K. Result: Shikonin treated mice group exhibited better and faster skin burn wound healing in comparison with the controls. The proliferation of new skin cells and hair follicle regeneration in the wound site of the shikonin treated group was more active. The recruitment of macrophages in shikonin treated group was inhibited inturn decreased the expression of inflammatory factors. However, LY294002 inhibited the shikonin-mediated PI3K/Akt signaling pathway and affected the wound healing process. Conclusion: In conclusion, this study strengthens the hypothesis that bioactive small molecule, shikonin, inhibits inflammation, promotes wound healing and has a significant protective effect on the deep hair follicles against burn skin injury by activating the PI3K/Akt signaling pathway.

The p38 MAPK/NF-κB pathway mediates GLT-1 up-regulation during cerebral ischemic preconditioning-induced brain ischemic tolerance in rats.

Our previous finding suggests that p38 MAPK contributes to the GLT-1 upregulation during induction of brain ischemic tolerance by cerebral ischemic preconditioning (CIP), however, the underlying mechanism is still unclear. Here, we investigated the molecular mechanisms underlying the CIP-induced GLT-1 upregulation by using Western blotting, Co-immunoprecipitation (Co-IP), electrophoretic mobility shift assay (EMSA) and thionin staining in rat hippocampus CA1 subset. We found that application of BAY11-7082 (an inhibitor of NF-κB), or dihydrokainate (an inhibitor of GLT-1), or SB203580 (an inhibitor of p38 MAPK) could attenuate the CIP-induced neuronal protection in hippocampus CA1 region of rats. Moreover, CIP caused rapid activation of NF-κB, as evidenced by nuclear translocation of NF-κB p50 protein, which led to active p50/p65 dimer formation and increased DNA binding activity. GLT-1 was also increased after CIP. Pretreatment with BAY11-7082 blocked the CIP-induced GLT-1 upregulation. The above results suggest that NF-κB participates in GLT-1 up-regulation during the induction of brain ischemic tolerance by CIP. We also found that pretreatment with SB203580 caused significant reduction of NF-κB p50 protein in nucleus, NF-κB p50/p65 dimer nuclear translocation and DNA binding activity of NF-κB. Together, we conclude that p38 MAPK/NF-κB pathway participates in the mediation of GLT-1 up-regulation during the induction of brain ischemic tolerance induced by CIP.

Intermittent hypobaric hypoxia preconditioning induced brain ischemic tolerance by up-regulating glial glutamate transporter-1 in rats.

Several studies showed that the up-regulation of glial glutamate transporter-1 (GLT-1) participates in the acquisition of brain ischemic tolerance induced by cerebral ischemic preconditioning or ceftriaxone pretreatment in rats. To explore whether GLT-1 plays a role in the acquisition of brain ischemic tolerance induced by intermittent hypobaric hypoxia (IH) preconditioning (mimicking 5,000 m high-altitude, 6 h per day, once daily for 28 days), immunohistochemistry and western blot were used to observe the changes in the expression of GLT-1 protein in hippocampal CA1 subfield during the induction of brain ischemic tolerance by IH preconditioning, and the effect of dihydrokainate (DHK), an inhibitor of GLT-1, on the acquisition of brain ischemic tolerance in rats. The basal expression of GLT-1 protein in hippocampal CA1 subfield was significantly up-regulated by IH preconditioning, and at the same time astrocytes were activated by IH preconditioning, which appeared normal soma and aplenty slender processes. The GLT-1 expression was decreased at 7 days after 8-min global brain ischemia. When the rats were pretreated with the IH preconditioning before the global brain ischemia, the down-regulation of GLT-1 protein was prevented clearly. Neuropathological evaluation by thionin staining showed that 200 nmol DHK blocked the protective role of IH preconditioning against delayed neuronal death induced normally by 8-min global brain ischemia. Taken together, the up-regulation of GLT-1 protein participates in the acquisition of brain ischemic tolerance induced by IH preconditioning in rats.

High expression of GLT-1 in hippocampal CA3 and dentate gyrus subfields contributes to their inherent resistance to ischemia in rats.

It is well known that neurons in the CA3 and dentate gyrus (DG) subfields of the hippocampus are resistant to short period of ischemia which is usually lethal to pyramidal neurons in hippocampal CA1 subfield. The present study was undertaken to clarify whether the inherent higher resistance of neurons in CA3 and DG to ischemia is associated with glial glutamate transporter-1 (GLT-1) in rats. Western blot analysis and immunohistochemistry assay showed that the basal expressions of GLT-1 in both CA3 and DG were much higher than that in CA1 subfield. Mild global brain ischemia for 8 min induced delayed death of almost all CA1 pyramidal neurons and marked GLT-1 down-regulation in the CA1 subfield, but it was not lethal to the neurons in either CA3 or DG and induced GLT-1 up-regulation and astrocyte activation showed normal soma and aplenty slender processes in the both areas. When the global brain ischemia was prolonged to 25 min, neuronal death was clearly observed in CA3 and DG accompanied with down-regulation of GLT-1 expression and abnormal astrocytes represented with hypertrophic somas, but shortened processes. After down-regulating of GLT-1 expression and function by its antisense oligodeoxynucleotides or inhibiting GLT-1 function by dihydrokainate, an inhibitor of GLT-1, the mild global brain ischemia for 8 min, which usually was not lethal to CA3 and DG neurons, induced the neuronal death in CA3 and DG subfields. Taken together, the higher expression of GLT-1 in the CA3 and DG contributes to their inherent resistance to ischemia.