Elucidation of the Role of TRPV1, VEGF-A, TXA2, Redox Homeostasis, and Inflammatory Cascades in Protection against Cold Injuries by Herbosomal-Loaded PEG-Poloxamer Topical Formulation.

Abstract

High-altitude regions, cold deserts, permafrost regions, and the polar region have some of the severest cold conditions on earth and pose immense perils of cold injuries to exposed individuals. Accidental and unintended exposures to severe cold, either unintentionally or due to occupational risks, can greatly increase the risk of serious conditions including hypothermia, trench foot, and cold injuries like frostbite. Cold-induced vasoconstriction and intracellular/intravascular ice crystal formation lead to hypoxic conditions at the cellular level. The condition is exacerbated in individuals having inadequate and proper covering and layering, particularly when large area of the body are exposed to extremely cold environments. There is a paucity of preventive and therapeutic pharmacological modalities that have been explored for managing and treating cold injuries. Given this, an efficient modality that can potentiate the healing of frostbite was investigated by studying various complex pathophysiological changes that occur during severe cold injuries. In the current research, we report the effectiveness and healing properties of a standardized formulation, i.e., a herbosomal-loaded PEG-poloxamer topical formulation (n-HPTF), on frostbite. The intricate mechanistic pathways modulated by the novel formulation have been elucidated by studying the pathophysiological sequelae that occur following severe cold exposures leading to frostbite. The results indicate that n-HPTF ameliorates the outcome of frostbite, as it activates positive sensory nerves widely distributed in the epidermis transient receptor potential vanilloid 1 (TRPV1), significantly (p < 0.05) upregulates cytokeratin-14, promotes angiogenesis (VEGF-A), prominently represses the expression of thromboxane formation (TXA2), and significantly (p < 0.05) restores levels of enzymatic (glutathione reductase, superoxide dismutase, and catalase) and nonenzymatic antioxidants (glutathione). Additionally, n-HPTF attenuates oxidative stress and the expression of inflammatory proteins PGF-2α, NFκB-p65, TNF-α, IL-6, IL-1β, malondialdehyde (MDA), advanced oxidative protein products (AOPP), and protein carbonylation (PCO). Masson's Trichrome staining showed that n-HPTF stimulates cellular proliferation, and increases collagen fiber deposition, which significantly (p < 0.05) promotes the healing of frostbitten tissue, as compared to control. We conclude that protection against severe cold injuries by n-HPTF is mediated via modulation of pathways involving TRPV1, VEGF-A, TXA2, redox homeostasis, and inflammatory cascades. The study is likely to have widespread implications for the prophylaxis and management of moderate-to-severe frostbite conditions.