Celastrol enhances the viability of random-pattern skin flaps by regulating autophagy through the AMPK-mTOR-TFEB axis.

In reconstructive and plastic surgery, random-pattern skin flaps (RPSF) are often used to correct defects. However, their clinical usefulness is limited due to their susceptibility to necrosis, especially on the distal side of the RPSF. This study validates the protective effect of celastrol (CEL) on flap viability and explores in terms of underlying mechanisms of action. The viability of different groups of RPSF was evaluated by survival zone analysis, laser doppler blood flow, and histological analysis. The effects of CEL on flap angiogenesis, apoptosis, oxidative stress, and autophagy were evaluated by Western blot, immunohistochemistry, and immunofluorescence assays. Finally, its mechanistic aspects were explored by autophagy inhibitor and Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) inhibitor. On the seventh day after surgery, the survival area size, blood supply, and microvessel count of RPSF were augmented following the administration of CEL. Additionally, CEL stimulated angiogenesis, suppressed apoptosis, and lowered oxidative stress levels immediately after elevated autophagy in ischemic regions; These effects can be reversed using the autophagy inhibitor chloroquine (CQ). Specifically, CQ has been observed to counteract the protective impact of CEL on the RPSF. Moreover, it has also been discovered that CEL triggers the AMPK-mTOR-TFEB axis activation in the area affected by ischemia. In CEL-treated skin flaps, AMPK inhibitors were demonstrated to suppress the AMPK-mTOR-TFEB axis and reduce autophagy levels. This investigation suggests that CEL benefits the survival of RPSF by augmenting angiogenesis and impeding oxidative stress and apoptosis. The results are credited to increased autophagy, made possible by the AMPK-mTOR-TFEB axis activation.

Limonin Inhibits IL-1ß-Induced Inflammation and Catabolism in Chondrocytes and Ameliorates Osteoarthritis by Activating Nrf2.

Osteoarthritis (OA), a degenerative disorder, is considered to be one of the most common forms of arthritis. Limonin (Lim) is extracted from lemons and other citrus fruits. Limonin has been reported to have anti-inflammatory effects, while inflammation is a major cause of OA; thus, we propose that limonin may have a therapeutic effect on OA. In this study, the therapeutic effect of limonin on OA was assessed in chondrocytes in vitro in IL-1ß induced OA and in the destabilization of the medial meniscus (DMM) mice in vivo. The Nrf2/HO-1/NF-κB signaling pathway was evaluated to illustrate the working mechanism of limonin on OA in chondrocytes. In this study, it was found that limonin can reduce the level of IL-1ß induced proinflammatory cytokines such as INOS, COX-2, PGE2, NO, TNF-α, and IL-6. Limonin can also diminish the biosynthesis of IL-1ß-stimulated chondrogenic catabolic enzymes such as MMP13 and ADAMTS5 in chondrocytes. The research on the mechanism study demonstrated that limonin exerts its protective effect on OA through the Nrf2/HO-1/NF-κB signaling pathway. Taken together, the present study shows that limonin may activate the Nrf2/HO-1/NF-κB pathway to alleviate OA, making it a candidate therapeutic agent for OA.

20-Deoxyingenol alleviates osteoarthritis by activating TFEB in chondrocytes.

Osteoarthritis (OA) is an age-related degenerative disease and currently cannot be cured. Transcription factor EB (TFEB) is one of the major transcriptional factors that regulates autophagy and lysosomal biogenesis. TFEB has been shown to be an effective therapeutic target for many diseases including OA. The current study explores the therapeutic effects of 20-Deoxyingenol (20-DOI) on OA as well as its working mechanism on TFEB regulation. The in vitro study showed that 20-DOI may suppress apoptosis and senescence induced by oxidative stress in chondrocytes; it may also promote the nuclear localization of TFEB in chondrocytes. Knock-down of TFEB compromised the effects of 20-DOI on apoptosis and senescence. The in vivo study demonstrated that 20-DOI may postpone the progression of OA in mouse destabilization of the medial meniscus (DMM) model; it may also suppress apoptosis and senescence and promote the nuclear localization of TFEB in chondrocytes in vivo. This work suggests that 20-Deoxyingenol may alleviate osteoarthritis by activating TFEB in chondrocytes, while 20-DOI may become a potential drug for OA therapy.

Hydrogen sulfide protects against IL-1ß-induced inflammation and mitochondrial dysfunction-related apoptosis in chondrocytes and ameliorates osteoarthritis.

The inflammatory environment and excessive chondrocyte apoptosis have been demonstrated to play crucial roles in the onset of osteoarthritis (OA). Hydrogen sulfide (H2 S), a gaseous signalling molecule, exerts an inhibitory effect on inflammation and apoptosis in several degenerative diseases. However, the protective effect of H2 S against OA has not been fully clarified, and its underlying mechanism should be examined further. In the current study, the role of endogenous H2 S in the pathogenesis of OA and its protective effects on interleukin (IL)-1ß-induced chondrocytes were identified. Our data revealed decreased H2 S expression in both human degenerative OA cartilage tissue and IL-1ß-induced chondrocytes. Pretreatment with the H2 S donor sodium hydrosulfide (NaHS) dramatically attenuated IL-1ß-induced overproduction of inflammatory cytokines and improved the balance between anabolic and catabolic chondrocyte capacities, and these effects were dependent on PI3K/AKT pathway-mediated inhibition of nuclear factor kappa B (NF-κB). Moreover, mitochondrial dysfunction-related apoptosis was significantly reversed by NaHS in IL-1ß-stimulated chondrocytes. Mechanistically, NaHS partially suppressed IL-1ß-induced phosphorylation of the mitogen-activated protein kinase (MAPK) cascades. Furthermore, in the destabilization of the medial meniscus mouse model, OA progression was ameliorated by NaHS administration. Taken together, these results suggest that H2 S may antagonize IL-1ß-induced inflammation and mitochondrial dysfunction-related apoptosis via selective suppression of the PI3K/Akt/NF-κB and MAPK signalling pathways, respectively, in chondrocytes and may be a potential therapeutic agent for the treatment of OA.

ß-Hydroxyisovalerylshikonin inhibits IL-1ß-induced chondrocyte inflammation via Nrf2 and retards osteoarthritis in mice.

Osteoarthritis is a chronic degenerative disease characterized by cartilage destruction. It is the fourth most disabling disease worldwide and is currently incurable. Inflammation and extracellular matrix (ECM) degradation are considered to be substantial reasons for accelerating the progression of OA. ß-Hydroxyisoamylshikonin (ß-HIVS) is a natural naphthoquinone compound with anti-inflammatory and antioxidant activity. However, the effect of ß-HIVS on OA is still unclear. In this study, we found that ß-HIVS can down-regulate the expression of NO, PEG2, IL-6, TNF-α, COX-2, and iNOS, suggesting its anti-inflammatory effects in chondrocytes; we also found that ß-HIVS may down-regulate the expression of ADAMTS5 and MMP13 and up-regulate the expression of aggrecan and collagen II to inhibit the degradation of ECM. Mechanistically, ß-HIVS inhibited the NFκB pathway by activating the Nrf2/HO-1 axis, thereby exerting its anti-inflammatory and inhibitory effects on ECM degradation. In vivo experiments also proved the therapeutic effects of ß-HIVS on OA in mice, and Nrf2 is the target of ß-HIVS. These findings indicate that ß-HIVS may become a new drug for the treatment of OA.

Akebia Saponin D suppresses inflammation in chondrocytes via the NRF2/HO-1/NF-κB axis and ameliorates osteoarthritis in mice.

As an ordinary joint vestigial disease, osteoarthritis (OA) contributes to a considerable proportion of disability cases worldwide. Inflammation, as the main pathological factor, mediates the occurrence and development of OA. Akebia Saponin D (ASD), also known as Asperosaponin VI, is one of the active components extracted from Dipsaci Radix and is rich in Dipsacus loose tea. It has shown sound therapeutic effects on various diseases; nevertheless, its role in OA therapy is not completely understood. This study demonstrated the anti-inflammatory activity of ASD in OA through a series of in vivo and in vitro experiments. In vitro experiments revealed that ASD might prohibit the production of inflammatory mediators in IL-1ß treated chondrocytes such as COX-2, iNOS, NO, PGE2, IL-6, and TNF-α. Meanwhile, it may also inhibit the production of ADAMTS-5 and MMP13 and promote the production of Aggrecan and Collagen II. The mechanism study demonstrated that ASD exerted an anti-inflammatory effect by activating the NRF2 target, upregulating the expression of HO-1, and preventing P65 from binding to DNA. In vivo experiments demonstrated that ASD might improve the progression of OA in a DMM mouse model. These research results provide evidence for the potential application of ASD in OA therapy.

Dual regulation of microglia and neurons by Astragaloside IV-mediated mTORC1 suppression promotes functional recovery after acute spinal cord injury.

Inflammation and neuronal apoptosis contribute to the progression of secondary injury after spinal cord injury (SCI) and are targets for SCI therapy; autophagy is reported to suppress apoptosis in neuronal cells and M2 polarization may attenuate inflammatory response in microglia, while both are negatively regulated by mTORC1 signalling. We hypothesize that mTORC1 suppression may have dual effects on inflammation and neuronal apoptosis and may be a feasible approach for SCI therapy. In this study, we evaluate a novel inhibitor of mTORC1 signalling, Astragaloside IV (AS-IV), in vitro and in vivo. Our results showed that AS-IV may suppress mTORC1 signalling both in neuronal cells and microglial cells in vitro and in vivo. AS-IV treatment may stimulate autophagy in neuronal cells and protect them against apoptosis through autophagy regulation; it may also promote M2 polarization in microglial cells and attenuate neuroinflammation. In vivo, rats were intraperitoneally injected with AS-IV (10 mg/kg/d) after SCI, behavioural and histological evaluations showed that AS-IV may promote functional recovery in rats after SCI. We propose that mTORC1 suppression may attenuate both microglial inflammatory response and neuronal apoptosis and promote functional recovery after SCI, while AS-IV may become a novel therapeutic medicine for SCI.

BRD4 inhibition regulates MAPK, NF-κB signals, and autophagy to suppress MMP-13 expression in diabetic intervertebral disc degeneration.

Diabetes mellitus may lead to intervertebral disc degeneration (IVDD). Matrix metalloproteinase-13 (MMP-13) is one of the major catabolic factors in extracellular matrix (ECM) metabolism of nucleus pulposus cells (NPCs) and contributes to diabetic IVDD. Bromodomain-containing protein 4 (BRD4) is a member of the bromodomain and extraterminal protein family and is implicated in chronic inflammation. Here, we report that the expression of BRD4 and MMP-13 was elevated in diabetic nucleus pulposus tissues as well as in advanced glycation end products (AGEs)-treated NPCs; also, the regulatory effect of BRD4 on MMP-13 was studied. We found that MMP-13 was regulated by MAPK and NF-κB signaling as well as autophagy in AGEs-treated NPCs. Next, we explored the role of BRD4 in regulation of MAPK, NF-κB signaling, and autophagy. The results showed that BRD4 is the upstream regulator of all of these 3 factors, and inhibition of BRD4 may suppress MAPK and NF-κB signaling while activating autophagy in AGEs-treated NPCs. Finally, we demonstrated that BRD4 inhibition may suppress MMP-13 expression in diabetic NPCs in vitro as well as in vivo; meanwhile, it may preserve ECM in diabetic rats. Our study demonstrates that inhibition of BRD4 may suppress MAPK and NF-κB signaling and activate autophagy to suppress MMP-13 expression in diabetic IVDD, and diabetic IVDD may be compromised by BRD4 inhibitors.-Wang, J., Hu, J., Chen, X., Huang, C., Lin, J., Shao, Z., Gu, M., Wu, Y., Tian, N., Gao, W., Zhou, Y., Wang, X., Zhang, X. BRD4 inhibition regulates MAPK, NF-κB signals, and autophagy to suppress MMP-13 expression in diabetic intervertebral disc degeneration.