Vitamin D plays a protective role in osteoarthritis by regulating AMPK/mTOR signalling pathway to activate chondrocyte autophagy.

OBJECTIVES: The deletion of chondrocyte autophagy seems to play a key role in the pathogenesis of osteoarthritis (OA). Patients with OA often have vitamin D (VD) deficiency, and VD supplementation can improve pain and alleviate the progression of joint structures in patients. In this study, we aimed to investigate whether VD could enhance autophagy by activating the adenosine monophosphate activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signalling pathway and protect against OA. METHODS: In this study, the levels of target proteins and genes were examined by western blot and qRT-PCR. Apoptotic cells were detected using TUNEL staining. Characteristics of autophagy were observed by LysoTracker red staining, mRFP-GFP-LC3 adenovirus transfection, and transmission electron microscopy. siRNA-mediated AMPK and mTOR knockdown were used to investigate the role of the AMPK/ mTOR signalling pathway in VD-induced autophagy. Haematoxylin and eosin and safranin-O/fast green staining were used detect cartilage alterations. RESULTS: We suggested that VD significantly reduced chondrocyte death and alleviated extracellular matrix degradation. Further studies showed that VD promoted the expression of the autophagy-related protein LC3II through the AMPK/mTOR signalling pathway in chondrocytes, activated lysosome activity, promoted the formation of autophagy-associated lysosomes, which played a crucial role in the degradation of intracellular organelles and maintained homeostasis. The anti-apoptotic effect of VD on chondrocytes was associated with the activation of autophagy. The group of AMPK-normal and mTOR-knockdown in the presence of VD inhibited chondrocyte apoptosis by promoting autophagy. CONCLUSIONS: This study highlights that VD can activate chondrocyte autophagy through the AMPK/mTOR signalling pathway.

Copper transporter 1 in human colorectal cancer cell lines: Effects of endogenous and modified expression on oxaliplatin cytotoxicity.

Oxaliplatin-based chemotherapy is the mainstay for the treatment of advanced colorectal cancer. Copper transporter proteins have been implicated in the transport of platinum-based anticancer drugs, but their expression in human colorectal cancer cell lines and roles in controlling their sensitivity to oxaliplatin are not well studied or understood. The endogenous and modified expression of copper uptake transporter 1 (hCTR1) was studied in a panel of human colorectal cancer cell lines (DLD-1, SW620, HCT-15 and COLO205) with ~20-fold variation in oxaliplatin sensitivity. hCTR1 protein was expressed more abundantly than ATP7A and ATP7B proteins, but with broadly similar levels and patterns of expression across four colorectal cancer cell lines. In a colorectal cancer cell-line background (DLD-1), stable transfection of the hCtr1 gene enhanced hCTR1 protein expression and increased the sensitivity of the cells to the cytotoxicity of copper and oxaliplatin. Treatment with copper chelators (ammonium tetrathiomolybdate, bathocuproinedisulfonic acid and D-penicillamine) increased expression of hCTR1 protein in DLD-1 and SW620 cells, and potentiated the cytotoxicity of oxaliplatin in DLD-1 but not SW620 cells. Treatment with copper chloride altered neither the expression of copper transporters nor cytotoxicity of oxaliplatin in colorectal cancer lines. In conclusion, human colorectal cancer cell lines consistently express hCTR1 protein despite their variable sensitivity to oxaliplatin. Genetic or pharmacological modification of hCTR1 protein expression may potentiate oxaliplatin sensitivity in some but not all colorectal cancer cell lines.

ABC Transporter Inhibitors in Reversing Multidrug Resistance to Chemotherapy.

The superfamily of human ATP-binding cassette (ABC) transporters comprises seven subfamilies (ABCA to G) with 48 members. In addition to their profound physiological and pharmacological functions, ABC transporters play important roles in instigating multidrug resistance (MDR) in cancer by mediating the efflux of many anticancer drugs, particularly, ABCB1, ABCG2 and ABCC subfamily members. Previous development of ABCB1 transporter inhibitors has provided insights into seeking novel strategies in developing new classes of compound that inhibit ABCB1 and other MDRrelated ABC transporters. We herein review and evaluate current evidence in this area, with an emphasis on experimental and investigational agents that are under preclinical and clinical tests, including tyrosine kinase inhibitors, natural products, microRNAs and novel chemical entities. New strategies targeting ABC transporters in cancer stem cells and future perspectives in this field are also discussed.