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(2+) signaling. In osteoarthritic chondrocytes, Ca(2+) 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(2+) 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(2+) 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(2+) 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).