Comparative Study on the Protective Effect of Thiamine and Thiamine Pyrophosphate Against Hydroxychloroquine-Induced Cardiomyopathy in Rats

Background: Hydroxychloroquine (HCQ), widely used in autoimmune and inflammatory diseases, has been associated with cardiotoxicity driven by oxidative, mitochondrial, and metabolic disturbances. However, no comparative evidence exists regarding whether thiamine, thiamine pyrophosphate (TPP), or their combination (TTPC) can mitigate HCQ-induced myocardial injury. Objective: This study examined the biochemical and histopathological effects of thiamine, TPP, and their combination in a rat model of HCQ-induced cardiomyopathy. Methods: Thirty male Wistar rats were assigned to five groups: healthy control, HCQ, thiamine + HCQ, TPP + HCQ, and TTPC + HCQ. Thiamine (20 mg/kg, intraperitoneal), TPP (20 mg/kg, intraperitoneal), or TTPC (20 mg/kg each, intraperitoneal) was administered once daily, followed by HCQ (120 mg/kg, oral, twice daily). After seven days, cardiac tissue was analyzed for MDA, tGSH, SOD, and CAT, while serum TnI, lactate, and LDH were measured from tail-vein blood samples. Cardiac samples underwent histopathological examination. Results: HCQ exposure markedly increased MDA, TnI, LDH, and lactate levels while reducing tGSH, SOD, and CAT, indicating severe oxidative and metabolic insult. Thiamine co-treatment failed to ameliorate these disturbances. Conversely, TPP restored redox balance, attenuated biomarker elevations, and improved cardiac biochemical profiles. TTPC produced comparable improvements but did not exceed those of TPP alone. Histopathologically, HCQ caused pronounced myocyte degeneration and mononuclear infiltration, whereas TPP and TTPC groups showed only mild inflammatory changes with preserved myocardial architecture. Conclusions: HCQ induces a marked redox imbalance accompanied by well-defined histopathological myocardial degeneration. TPP afforded robust cardio-protection, whereas thiamine offered no meaningful benefit. Collectively, these findings position TPP as a biologically plausible, clinically relevant candidate for mitigating HCQ-induced cardiomyopathy. © 2025 by the authors.