Lactate-upregulated NADPH-dependent NOX4 expression via HCAR1/PI3K pathway contributes to ROS-induced osteoarthritis chondrocyte damage.

Increasing evidence shows that metabolic factors are involved in the pathological process of osteoarthritis (OA). Lactate has been shown to contribute to the onset and progression of diseases. While whether lactate is involved in the pathogenesis of OA through impaired chondrocyte function and its mechanism remains unclear. This study confirmed that serum lactate levels were elevated in OA patients compared to healthy controls and were positively correlated with synovial fluid lactate levels, which were also correlated with fasting blood glucose, high-density lipoprotein, triglyceride. Lactate treatment could up-regulate expressions of the lactate receptor hydroxy-carboxylic acid receptor 1 (HCAR1) and lactate transporters in human chondrocytes. We demonstrated the dual role of lactate, which as a metabolite increased NADPH levels by shunting glucose metabolism to the pentose phosphate pathway, and as a signaling molecule up-regulated NADPH oxidase 4 (NOX4) via activating PI3K/Akt signaling pathway through receptor HCAR1. Particularly, lactate could promote reactive oxygen species (ROS) generation and chondrocyte damage, which was attenuated by pre-treatment with the NOX4 inhibitor GLX351322. We also confirmed that lactate could increase expression of catabolic enzymes (MMP-3/13, ADAMTS-4), reduce the synthesis of type II collagen, promote expression of inflammatory cytokines (IL-6, CCL-3/4), and induce cellular hypertrophy and aging in chondrocytes. Subsequently, we showed that chondrocyte damage mediated by lactate could be reversed by pre-treatment with N-Acetyl-l-cysteine (NAC, ROS scavenger). Finally, we further verified in vivo that intra-articular injection of lactate in Sprague Dawley (SD) rat models could damage cartilage and exacerbate the progression of OA models that could be countered by the NOX4 inhibitor GLX351322. Our study highlights the involvement of lactate as a metabolic factor in the OA process, providing a theoretical basis for potential metabolic therapies of OA in the future.

Intraperitoneal administration of the globular adiponectin gene ameliorates diabetic nephropathy in Wistar rats.

The present study investigated the potential effects of the long-term expression of exogenous adiponectin (ADPN) on normal and diabetic kidneys. Type 2 diabetes mellitus models were induced by high-lipid and high-sucrose feeding plus intraperitoneal injection of streptozotocin. The recombinant plasmid pIRES2-EGFP-gAd, which is able to co-express globular ADPN (gAd) and enhanced green fluorescent protein (EGFP), was intraperitoneally injected into rat models mediated by Lipofectamine. In total, 32 Wistar rats were randomly assigned into four groups: the normal control group, the diabetes group, the diabetes group treated with pIRES2-EGFP-gAd and the diabetes group treated with pIRES2-EGFP. After 12 weeks, serum biochemistry and urine albumin levels were measured. The kidneys were collected to assess the generation of reactive oxygen species (ROS) and the renal pathological changes were observed by light microcopy. The protein expression of endothelial nitric oxide synthase (eNOS), transforming growth factor-ß1 (TGF-ß1) and phosphorylated adenosine monophosphate-activated protein kinase (p-AMPK) were determined by an immunohistochemical staining method and western blot analysis. Intraperitoneal injection of the human gAd gene via Lipofectamine resulted in abundant ADPN protein in the kidney. In the diabetic rats, the delivery of the exogenous gAd gene ameliorated the progression of diabetic nephropathy (DN). ADPN attenuated urine albumin excretion in the diabetic rats. ADPN also mitigated glomerular mesangial expansion, reduced the generation of ROS and prevented interstitial fibrosis. In addition, the expression of gAd inhibited the renal expression of TGF-ß1, promoted the protein expression of eNOS and activated the opening of the AMPK signaling pathway in the renal tissues of the diabetic rats. Despite the effects of ADPN on DN being controversial, these observations indicate that the supplementation of ADPN is beneficial in ameliorating DN in rats.

Adiponectin inhibits the generation of reactive oxygen species induced by high glucose and promotes endothelial NO synthase formation in human mesangial cells.

The aim of this study was to investigate the effects of adiponectin (ADPN) on high glucose (HG)-induced reactive oxygen species (ROS) and the formation of endothelial nitric oxide (NO) synthase (eNOS) in human glomerular mesangial cells (HMCs), as well as to determine which signaling pathways are modulated by ADPN and the mechanisms involved. HMCs cultured in vitro were randomly divided into 4 groups: the control, HG, HG + globular adiponectin (gAd) and HG + gAd + adenine arabinoside (AraA). The generation of ROS was detected using a fluorescent probe. The mRNA expression and protein levels of eNOS were measured by RT-PCR and western blot analysis, respectively. The phosphorylation of AMP-activated protein kinase (AMPK) was assessed by western blot analysis. HMCs treated with ADPN revealed the time-dependent phosphorylation of AMPK. The treatment of HMCs with HG resulted in increased release of ROS and decreased expression of eNOS compared to the control group (p<0.05). Cells treated with ADPN showed a decrease in HG-induced ROS (p<0.05) and an upregulated eNOS expression. The effects of gAd were partly blocked by the AMPK inhibitor, AraA. The results from the present study show that ADPN inhibits the generation of HG-induced ROS in HMCs; it also stimulates eNOS activity, which has a protective effect. The mechanism partly occurs through the stimulation of the AMPK signaling pathway.

[Renoprotective effect of adiponectin through an antioxidant mechanism in streptozotocin- induced diabetic rats].

OBJECTIVE: To investigate the renoprotective effect of adiponectin in streptozotocin (STz)-induced diabetic rats and explore its association with oxidation stress. METHODS: Type 2 diabetes mellitus was induced in rats by high-lipids and high-sucrose feeding and intraperitoneal STZ injection. The recombinant plasmid pIRES2-EGFP-gAd expressing globular adiponectin was intraperitoneally injected in the rats mediated by liposome. Thirty-two Wistar rats were randomized into 4 groups, namely the normal control group (NC), diabetic group without any therapy (DM), diabetic group treated with pIRES2-EGFP-gAd (DA) and diabetic group treated with pIRES2-EGFP (DP). After the corresponding treatments for 8 weeks, the blood glucose, HbA1c and urine albumin excretion rate (UAER) were measured, and the kidneys were collected to determine the production of reactive oxygen species (ROS) and assess renal pathologies. Immunohistochemistry and Western blot were employed to determine the protein levels of endothelial nitric oxide synthesis (eNOS) and phosphorylated AMP-activated protein kinase (pAMPK). RESULTS: UAER and ROS production increased significantly in DM group as compared with that in the control group (P<0.05), while no significant differences were found in UARE among the DM, DA, and DP groups (P>0.05). Blood glucose level, HbA1c and ROS were significantly decreased in DA group in comparison with those in DM group (P<0.05). Glomerular hypetrophy, mesangial expansion, basal membrane thickening, tubular epithelial cells cavitation and exfoliation, and mononuclear lymphocyte infiltration occurred in DM group, while these changes were ameliorated in gAd transfection group. The renal expression levels of eNOS and p-AMPK proteins in DM group were significantly lower than those in the control group (P<0.05) and gAd transfection group (P<0.05). CONCLUSIONS: The renoprotective effect of adiponectin may be at least partially mediated by the activation of the AMPK signaling passway, ROS production inhibition, relief of the oxidative stress, and up-regulation of eNOS expression in the renal tissue of diabetic rats.

[Edge detection and modeling in frontal facial contour image for plastic surgery].

OBJECTIVE: To find a new method for edge detection and modeling in frontal facial contour image. METHODS: Searching circle-based edge detection algorithm was developed on the basis of Sobel edge detector. Apriori knowledge of the facial contour and searching limitations as the minimum curvature radius, concave-convex property, and maximum edge disconnected distance were used to detect the edge of frontal facial contour. The frontal facial contour model was established with least squares curve fitting methods, and the relationship between the model rank and model precision was analyzed. RESULTS: The edge detected by the new method was consistent with the actual edge of the facial contour and the irrelevant edge was well eliminated. Variation of the 2,4,10 time models from the actual image were compared, which identified the 10 time model as the best one. CONCLUSION: The effectiveness and practicability of this new method for edge detection and modeling has been tested, which provides a theoretic basis for designing facial contouring image system.