Identification of adenine-N9-(methoxy)ethyl-β-bisphosphonate as NPP1 inhibitor attenuates NPPase activity in human osteoarthritic chondrocytes

CTGF regulates mineralization in human mature chondrocyte by controlling Pit-1 and modulating ANK via the BMP/Smad signalling

OBJECTIVE

Connective tissue growth factor (CTGF) exhibits potent proliferative, differentiated, and mineralizing effects, and is believed to be contribute to cartilage mineralization in Osteoarthritis (OA). However, the underlying mechanism of chondrocyte mineralization induced by CTGF remains obscure. As a key regulator of mineral responses, type III phosphate transporter 1 (Pit-1) has been associated with the pathogenesis of articular mineralization. Therefore, the primary objective of this study was to investigate whether CTGF influences the development of mature chondrocyte mineralization and the underlying mechanisms governing such mineralization.

METHODS

The effect of Connective tissue growth factor (CTGF) on human C-28/I2 chondrocytes were investigated. The chondrocytes were treated with CTGF or related inhibitors, and transfected with Overexpression and siRNA transfection of Type III Phosphate Transporter 1(Pit-1). Subsequently, the cells were subjected to Alizarin red S staining, PiPer Phosphate Assay Kit, Alkaline Phosphatase Diethanolamine Activity Kit, ELISA, RT-PCR or Western blot analysis.

RESULTS

Stimulation with Connective tissue growth factor (CTGF) significantly upregulated the expression of the Type III Phosphate Transporter 1(Pit-1) and mineralization levels in chondrocytes through activation of α5β1 integrin and BMP/Samd1/5/8 signaling pathways. Furthermore, treatment with overexpressed Pit-1 markedly increased the expression of Multipass Transmembrane Ankylosis (ANK) transporter in the cells. The inhibitory effect of CTGF receptor blockade using α5β1 Integrin blocking antibody was demonstrated by significantly suppressed the expression of Pit-1 and ANK transporter, as well as chondrocyte mineralization.

CONCLUSIONS

Our data indicate that Connective tissue growth factor (CTGF) plays a critical role inchondrocyte mineralization, which is dependent on the expression of the Type III Phosphate Transporter 1(Pit-1) and Multipass Transmembrane Ankylosis (ANK) transporter. Consequently, inhibition of CTGF activity may represent a novel therapeutic approach for the management of Osteoarthritis (OA).

Small molecular CD73 inhibitors: Recent progress and future perspectives

The occurrence and development of the tumor are very complex biological processes. In recent years, a large number of research data shows that CD73 is closely related to tumor growth and metastasis. It has been confirmed that the cascade hydrolysis of extracellular ATP to adenosine is one of the most important immunosuppressive regulatory pathways in the tumor microenvironment. The metabolite adenosine can mediate immunosuppression by activating adenosine receptor (such as A2A) on effector Immune cells and enable tumor cells to achieve immune escape. Therefore, attenuating or completely removing adenosine-mediated immunosuppression in the tumor microenvironment by inhibiting CD73 is a promising approach in the treatment of solid tumors. This paper focuses on the research progress of CD73 enzyme and CD73 small molecule inhibitors, and is expected to provide some insights into the development of small-molecule antitumor drugs targeting CD73.

Advances in CD73 inhibitors for immunotherapy: Antibodies, synthetic small molecule compounds, and natural compounds

Tumors, a disease with a high mortality rate worldwide, have become a serious threat to human health. Exonucleotide-5'-nucleotidase (CD73) is an emerging target for tumor therapy. Its inhibition can significantly reduce adenosine levels in the tumor microenvironment. It has a better therapeutic effect on adenosine-induced immunosuppression. In the immune response, extracellular ATP exerts immune efficacy by activating T cells. However, dead tumor cells release excess ATP, overexpress CD39 and CD73 on the cell membrane and catabolize this ATP to adenosine. This leads to further immunosuppression. There are a number of inhibitors of CD73 currently under investigation. These include antibodies, synthetic small molecule inhibitors and a number of natural compounds with prominent roles in the anti-tumor field. However, only a small proportion of the CD73 inhibitors studied to date have successfully reached the clinical stage. Therefore, effective and safe inhibition of CD73 in oncology therapy still holds great therapeutic potential. This review summarizes the currently reported CD73 inhibitors, describes their inhibitory effects and pharmacological mechanisms, and provides a brief review of them. It aims to provide more information for further research and development of CD73 inhibitors.

The Synthesis of Nucleoside 2',3'-Cyclic Monophosphate Analogs with Regio- and Stereospecificity

This article presents a new method for the rapid, stereoselective and regioselective synthesis of nucleoside 2',3'-O,O-phosphorothioate and 2',3'-O,O-phosphoroselenoate molecules. The method avoids the use of protection groups, chiral reagents, and chiral metal catalysts, as well as complicated chiral separations. This synthetic method has been applied successfully to all of the natural nucleosides. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Preparation of 2-chloro-1,3,2-dithiophospholane (6) Basic Protocol 2: Preparation of 2-cyanoethoxy-thio-dithiophospholane (8) Basic Protocol 3: Preparation of 2-cyanoethoxy-seleno-dithiophospholane (9) Basic Protocol 4: Preparation of uridine-2',3'-O,O-phosphorothioate (Sp, exo; 1A) Basic Protocol 5: Preparation of uridine-2',3'-O,O-phosphoroselenoate (Sp, exo; 11) Basic Protocol 6: Preparation of adenosine-2',3'-O,O-phosphorothioate (Sp, exo; 12) Basic Protocol 7: Preparation of thymidine-2',3'-O,O-phosphorothioate (Sp, exo; 13) Basic Protocol 8: Preparation of cytosine-2',3'-O,O-phosphorothioate (Sp, exo; 14) Basic Protocol 9: Preparation of guanosine-2',3'-O,O-phosphorothioate (Sp, exo; 15).

Addressing regio- and stereo-specificity challenges in the synthesis of nucleoside 2',3'-cyclic monophosphate analogs - a rapid and facile synthesis of nucleoside-2',3'-O,O-phosphoro-thioate or -selenoate, and elucidation of the origin of the rare specificity

A new facile, rapid, stereo- and regio-selective one-pot synthesis of nucleoside-2',3'-O,O-phosphorothioate and selenoate analogs has been developed. This method avoids the need for protection strategies and chiral reagents, chiral metal catalysts, or chiral separations. This synthetic method has been applied to all natural nucleosides (U/A/G/C/T). Furthermore, we have deciphered the origin of the stereo- and regio-selectivity of the reaction.

Recombinant expression of ecto-nucleotide pyrophosphatase/phosphodiesterase 4 (NPP4) and development of a luminescence-based assay to identify inhibitors

Nucleotide pyrophosphatase/phosphodiesterase 4 (NPP4) is a membrane-bound enzyme that hydrolyzes extracellular diadenosine polyphosphates such as diadenosine triphosphate (Ap₃A) and diadenosine tetraphosphate (Ap₄A) yielding mononucleotides. NPP4 on the surface of endothelial cells was reported to promote platelet aggregation by hydrolyzing Ap₃A to ADP, which activates pro-thrombotic G protein-coupled P2Y₁ and P2Y₁₂ receptors. Thus, NPP4 inhibitors have potential as novel antithrombotic drugs. In the present study we expressed soluble human NPP4 in Sf9 insect cells and established an enzyme assay using diadenosine tetraphosphate (Ap₄A) as a substrate. The reaction product ATP was quantified by luciferin-luciferase reaction in a 96-well plate format. The sensitive method displayed a limit of detection (LOD) of 14.6 nM, and a Z'-factor of 0.68 indicating its suitability for high-throughput screening. The new assay was applied for studying enzyme kinetics and led to the identification of the first NPP4 inhibitors.