Endo-Lysosomal Network Disorder Reprograms Energy Metabolism in SorL1-Null Rat Hippocampus.

Sortilin-related receptor 1 (SorL1) deficiency is a genetic predisposition to familial Alzheimer's disease (AD), but its pathology is poorly understood. In SorL1-null rats, a disorder of the global endosome-lysosome network (ELN) is found in hippocampal neurons. Deletion of amyloid precursor protein (APP) in SorL1-null rats could not completely rescue the neuronal abnormalities in the ELN of the hippocampus and the impairment of spatial memory in SorL1-null young rats. These in vivo observations indicated that APP is one of the cargoes of SorL1 in the regulation of the ELN, which affects hippocampal-dependent memory. When SorL1 is depleted, the endolysosome takes up more of the lysosome flux and damages lysosomal digestion, leading to pathological lysosomal storage and disturbance of cholesterol and iron homeostasis in the hippocampus. These disturbances disrupt the original homeostasis of the material-energy-subcellular structure and reprogram energy metabolism based on fatty acids in the SorL1-null hippocampus, instead of glucose. Although fatty acid oxidation increases ATP supply, it cannot reduce the levels of the harmful byproduct ROS during oxidative phosphorylation, as it does in glucose catabolism. Therefore, the SorL1-null rats exhibit hippocampal degeneration, and their spatial memory is impaired. Our research sheds light on the pathology of SorL1 deficiency in AD.

Pathological convergence of APP and SNCA deficiency in hippocampal degeneration of young rats.

The common pathogenesis of Alzheimer's disease (AD) and Parkinson's disease (PD) has been supported by biochemical, genetic and molecular evidence. Mitochondrial dysfunction is considered to be the common pathology in early AD and PD. The physiological regulation of APP and α-synuclein on mitochondria remains unclear, let alone whether they share common regulatory mechanisms affecting the development of neurodegenerative diseases. By studying gene knockout rats, the commonality of physiological APP and α-synuclein in maintaining mitochondrial function through calcium homeostasis regulation was revealed, which was critical in inhibiting hippocampal degeneration in young rats. APP and α-synuclein both control hippocampal mitochondrial calcium intake and outflow. In the mitochondrial calcium influx regulation, APP and α-synuclein are located on the mitochondrial-associated endoplasmic reticulum membrane (MAM) and converge to regulate the IP3R1-Grp75-VDAC2 axis. Mitochondrial calcium outflow is redundantly promoted by both α-synuclein and APP. Loss of APP or SNCA leads to mitochondrial calcium overload, thus enhancing aerobic respiration and ER stress, and ultimately causing excessive apoptosis in the hippocampus and spatial memory impairment in young rats. Based on this study, we believe that the physiological function impairment of APP and SNCA is the early core pathology to induce mitochondrial dysfunction at the early stage of AD and PD, while the IP3R1-Grp75-VDAC2 axis might be the common drug target of these two diseases.

[Corrigendum] Murine and Chinese cobra venom­derived nerve growth factor stimulate chondrogenic differentiation of BMSCs in vitro: A comparative study.

Subsequently to the publication of this paper, an interested reader drew to the authors' attention that Figs. 2 and 3, showing the results from experiments designed to assess the viability of bone­derived mesenchymal stem cells culture with or without nerve growth factors (NGFs) via fluorescein diacetate/propidium iodide or H&E staining respectively, contained apparently duplicated data panels within the figures. After having examined their original data, the authors have realized that these figures were inadvertently assembled incorrectly, and that there were also misassembled data panels in Fig. 6, which showed the secretion of types I and II collagens in bone­derived mesenchymal stem cells with or without NGFs. The corrected versions of Figs. 2, 3 and 6 are shown below and on the next page. Note that these errors did not significantly affect the results or the conclusions reported in this paper, and all the authors agree to this Corrigendum. Furthermore, the authors apologize to the readership for any inconvenience caused. [the original article was published in Molecular Medicine Reports 10.3892/mmr.2018.9307].

Artemisinin Ameliorates Osteoarthritis by Inhibiting the Wnt/ß-Catenin Signaling Pathway.

BACKGROUND/AIMS: Current drug therapies for osteoarthritis (OA) are not practical because of the cytotoxicity and severe side-effects associated with most of them. Artemisinin (ART), an antimalarial agent, is well known for its safety and selectivity to kill injured cells. Based on its anti-inflammatory activity and role in the inhibition of OA-associated Wnt/ß-catenin signaling pathway, which is crucial in the pathogenesis of OA, we hypothesized that ART might have an effect on OA. METHODS: The chondro-protective and antiarthritic effects of ART on interleukin-1-beta (IL-1ß)-induced and OA patient-derived chondrocytes were investigated in vitro using cell viability assay, glycosaminoglycan secretion, immunofluorescence, quantitative reverse transcription-polymerase chain reaction, and western blotting. We also used OA model rats constructed by anterior cruciate ligament transection and medial meniscus resection (ACLT+MMx) in the joints to investigate the effects of ART on OA by gross observation, morphological staining, immunohistochemistry, and enzyme-linked immunosorbent assay. RESULTS: ART exhibited potent anti-inflammatory effects by inhibiting the expression of proinflammatory chemokines and cytokines, including interleukin (IL)-1ß, IL-6, tumor necrosis factor alpha, and matrix metallopeptidase-13. It also showed favorable chondro-protective effect as evidenced by enhanced cell proliferation and viability, increased glycosaminoglycan deposition, prevention of chondrocyte apoptosis, and degeneration of cartilage. Further, ART inhibited OA progression and cartilage degradation via the Wnt/ß-catenin signaling pathway, suggesting that it might serve as a Wnt/ß-catenin antagonist to reduce inflammation and prevent cartilage degradation. CONCLUSION: In conclusion, ART alleviates IL-1ß-mediated inflammatory response and OA progression by regulating the Wnt/ß-catenin signaling pathway. Thereby, it might be developed as a potential therapeutic agent for OA.

Murine and Chinese cobra venom­derived nerve growth factor stimulate chondrogenic differentiation of BMSCs in vitro: A comparative study.

Mesenchymal stem cell (MSC)­based therapy has been commonly used in cartilage reconstruction, due to its self­renewing ability and multi­differentiation potential. Nerve growth factor (NGF) from cobra venom has been reported to regulate chondrogenesis of bone­derived MSCs (BMSCs) and chondrocyte metabolism. Therefore, the present study aimed to determine whether other sources of NGF behave in the same manner as NGF from natural venom. The present study compared the effects of NGF from two sources, the commercially purchased recombinant murine ß­NGF (mNGF) and cobra venom­derived NGF (cvNGF), on chondrogenesis of BMSCs by performing hematoxylin and eosin and fluorescein diacetate/propidium iodide staining, DNA and glycosaminoglycan quantization and reverse transcription­quantitative polymerase chain reaction to investigate cell morphology, viability, proliferation, glycosaminoglycan synthesis and cartilage­specific gene expression. The results demonstrated that cvNGF significantly accelerated cell proliferation and upregulated the expression of cartilage­specific genes, including aggrecan, SRY­box 9 and collagen type II α1 chain. Conversely, cvNGF reduced the expression levels of collagen type I α1 chain (a fibrocartilage marker), runt­related transcription factor 2 and enolase 2 compared with in the mNGF and control groups. In addition, Chinese cobra venom, which is the main resource of cvNGF, is abundant and inexpensive, thus greatly decreasing the cost. In conclusion, the present study demonstrated that cvNGF may be considered a potential growth factor for inducing chondrogenic differentiation of BMSCs.

Andrographolide protects chondrocytes from oxidative stress injury by activation of the Keap1-Nrf2-Are signaling pathway.

Recent studies have shown that andrographolide (AP) has the potential to be developed as a drug for therapy for osteoarthritis (OA). However, the role of AP in attenuating the progression of OA is still unknown. We hypothesized that its therapeutic effect may be associated with its antioxidant potential. In this study, we investigated the therapeutic effect of AP on chondrocytes injured by H2 O2 and the association with the oxidation-related signaling pathways through the detection of cell proliferation, cell viability, the expression of oxidative stress-specific genes (Sod1, Cat, and malonaldehyde [Mda]) and proteins (superoxide dismutase [SOD], catalase [CAT]) after a culture period of 3 and 5 days, respectively. Further exploration of the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) messenger RNA and protein was also performed. The results showed that 0.625 µg/ml and 2.5 µg/ml of AP decreased oxidative stress injury of chondrocytes by increasing cell proliferation reduced by H2 O2 and antioxidant enzyme activity, including SOD and CAT. Inflammation factors, such as matrix metallopeptidase 13 (Mmp13), tissue inhibitor of metalloproteinase 1 (Timp1), and interleukin-6 (Il6), were downregulated in the H2 O2 group with AP, demonstrating a decrease in the progression of OA. Pathway analyses identified that the kelch-like ECH-associated protein 1 (Keap1)-Nrf2-antioxidant response element (Are) pathway is an important mediator in AP therapy on H2 O2 -induced OA. This study indicates that AP exerts protection effects on oxidative stress via activation of the Keap1-Nrf2-Are pathway in chondrocytes injured by H2 O2 , which may be promising for the therapy of OA.

Collagen, agarose, alginate, and Matrigel hydrogels as cell substrates for culture of chondrocytes in vitro: A comparative study.

Autologous chondrocyte implantation (ACI) has emerged as a new approach to cartilage repair through the use of harvested chondrocytes. But the expansion of the chondrocytes from the donor tissue in vitro is restricted by limited cell numbers and dedifferentiation of chondrocytes. In this study, we used four types of hydrogels including agarose, alginate, Matrigel, and collagen type I hydrogels to serve as cell substrates and investigated the effect on proliferation and phenotype maintenance of chondrocytes. As a substrate for monolayer culture, collagen facilitated cell expansion and effectively suppressed the dedifferentiation of chondrocytes, as evidenced by fluorescein diacetate/propidium iodide (FDA/PI), hematoxylin-eosin staining (HE), Safranin O, immunofluorescenceassay, biochemistry analysis, and quantitative real-time polymerase chain reaction (qRT-PCR). Compared with that in agarose gels, alginate, and Matrigel, collagen accelerated cell proliferation and enhanced the expression of cartilage specific genes such as ACAN, SOX9, and COLII more markedly. Furthermore, significantly lower expression of COL I (an indicator of dedifferentiation) and COL X (the chondrocyte hypertrophy marker) was present in collagen group than in other groups. This indicated that collagen substrate can better support chondrocyte growth and maintain cell phenotype, due to that it might serve as a cartilage-like ECM to provide adhesive site for chondrocytes. In summary, collagen hydrogel is a promising cell substrate for chondrocytes culture for ACI.

Effect of NGF From Venom of Chinese Cobra (Naja Atra)on Chondrocytes Proliferation and Metabolism In Vitro.

Autologous chondrocyte implantation (ACI) is promising strategy for cartilage repair. However, chondrocyte phenotype is easily lost when expanded in vitro which defined as "dedifferentiation." To ensure successful therapy, an effective pro-chondrogenic agent is necessary to overcome the obstacle of limited cell numbers in the restoration process, and dedifferentiation is a prerequisite. In the present study, we investigated the chondro-protective effect of NGF from Chinese cobra venom on human chondrocytes by determination of its specific effect on cell viability, proliferation, morphology, GAG production, and cartilage specific gene expression. The results suggested that NGF showed no cytotoxicity to chondrocytes below the concentration of 16 µg/mL. DNA and glycosaminoglycan (GAG) content were, respectively, improved in NGF groups comparing to the control (P < 0.05). NGF up-regulate the gene expression of ACAN, SOX9, and COL2A1 while down-regulate the expression level of COL1A1 (P < 0.05). Moreover, the results of viability assay, hematoxylin-eosin, safranin O, and immunohistochemical staining also suggested better performances in NGF groups. NGF of 6 µg/mL shown lower cytotoxicity on chondrocytes, more glycosaminoglycans (GAGs) synthesis and up-regulated chondrogenic gene expression. This study may provide a basis for the development of a novel agent for the treatment of articular cartilage defects. J. Cell. Biochem. 118: 4308-4316, 2017. © 2017 Wiley Periodicals, Inc.