Bupivacaine in Combination with Sildenafil (Viagra) and Vitamin D3 Have Anti-inflammatory Effects in Osteoarthritic Chondrocytes

Aims: To treat osteoarthritic chondrocytes and thereby reduce the inflammation with a drug combination that primarily affects 5-HT- and ATP-evoked Ca signaling. In osteoarthritic chondrocytes, Ca signaling is elevated, resulting in increased production of ATP and inflammatory mediators. The expression of TLR4 and Na/K-ATPase was used to evaluate the inflammatory status of the cells.

Main Methods: Equine chondrocytes were collected from joints with mild structural osteoarthritic changes and cultured in monolayers. The cells were treated with a combination of bupivacaine (1 pM) and sildenafil (1 ​μM) in combination with vitamin D3 (100 ​nM). A high-throughput screening system, the Flexstation 3 microplate reader, was used to measure intra- and extracellular Ca signaling after exposure to 5-HT, glutamate, or ATP. Expression of inflammatory receptors was assessed by Western blotting.

Key Findings: Drug treatment substantially reduced 5-HT- and ATP-evoked intracellular Ca release and TLR4 expression compared to those in untreated chondrocytes. The combination of sildenafil, vitamin D3 together with metformin, as the ability to take up glucose is limited, increased Na/K-ATPase expression.

Significance: The combination of these three therapeutic substances at concentrations much lower than usually used, reduced expression of the inflammatory receptor TLR4 and increased the cell membrane enzyme Na/K-ATPase, which regulates cell volume and reduces increased intracellular Ca concentrations. These remarkable results indicate that this drug combination has disease-modifying osteoarthritis drug (DMOAD) properties and may be a new clinical therapy for osteoarthritis (OA).