Recent findings have demonstrated new therapeutic functions of cardiotonic steroids, a process that is termed drug repositioning. Despite the confirmed anti-inflammatory effects of cardiotonic steroids, their clinical use has been discouraged due to toxicity related to inhibition of the Na+/K+ ATPase. A novel synthetic compound derived from digoxin, 21‑benzylidene digoxin (21‑BD), does not inhibit this enzyme. Herein, we evaluated the anti-inflammatory and antinociceptive effects and acute toxicity of 21‑BD. Murine (Swiss mice) models of paw oedema induced by carrageenan, acetic acid-induced abdominal writhing, and formalin and acute toxicity tests were used. Oral administration of 21‑BD (0.3 mg/kg) showed a significant and prolonged inhibition of paw oedema. Histological analysis demonstrated a reduction in inflammatory cells and expression of inducible nitric oxide synthase (iNOS) in footpads 6 h after administration of carrageenan. 21‑BD (0.3 mg/kg) also reduced the levels of tumour necrosis factor (TNF)-α 2 and 4 h after carrageenan. 21‑BD demonstrated antinociceptive activity, inhibiting abdominal writhes at all tested doses. However, in the formalin test, 21‑BD did not present antinociceptive activity. In the acute toxicity test, 21‑BD did not cause symptoms of toxicity or mortality. The present study demonstrated, for the first time, that 21‑BD is safe and exhibits a marked anti-inflammatory activity in acute local inflammation. This effect might be a consequence of its ability to inhibit the release of the PMN leucocyte-derived mediators, including TNF-α, and iNOS expression as well as its inhibitory effect on oedema and PMN leucocyte infiltration.
Keywords: 21‑Benzylidene digoxin; Anti-inflammatory effect; Antinociceptive effect; Cardiotonic steroids; Paw edema.
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