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Astaxanthin is a powerful carotenoid antioxidant prevalent in marine organisms and approved as a food supplement. Recent studies have demonstrated Astaxanthin's beneficial attributes in various health states. Following initial reports of potential heat protective properties in Astaxanthin supplemented rats, we present here results of a novel study examining the effect of Astaxanthin supplementation on the heat shock response in rats in relation to core temperature (Tc) and the ensuing physiological strain. Two hours of heat stress at 41 °C during which rats developed their thermoregulatory hyperthermic plateau resulted in progressive increases in HSP72 and HSP27 in the Astaxanthin (Oleoresin)-treated group but not in the control (Olive oil) group. Enhanced elevation in HSPs suggests that Astaxanthin supplementation may augment the cellular stress protective response to heat stress.

Heatstroke (HS) is an acute, progressive life-threatening emergency. Animals, including military working dogs (IDFMWD), rapidly activate cytoprotective processes, e.g., heat shock proteins (HSPs) and antioxidative molecules, in response to heat stress. We hypothesized that serum HSPs (eHSP72) and oxidative stress markers would differ in IDFMWD with a history of HS compared with controls and thus could be used to detect susceptibility to recurrent HS. eHSPs concentration, oxidative stress markers, and systemic physiological parameters were studied in dogs with and without histories of HS, undergoing indoor or outdoor training. Treadmill physical performance tests (PPTs) were conducted indoors at 22 °C (groups C-I and HS-I) or outdoors under heat stress conditions of 36 °C; 60% humidity (groups C-O and HS-O). Pre-, immediately post-, and 45 min post-PPT heart rate (HR), respiratory rate, and rectal temperature (T(re)) were recorded in all dogs. Likewise, blood samples were collected and eHSP72, venous blood gas analysis, and lactate and creatine kinase activity (CK) were assayed. Serum uric acid (sUA) and total serum redox potential (TRP) were measured only in the indoor group. Immediately post-PPT under both environmental conditions, T(re), HR, eHSP, sUA, and TRP (only measured in indoor PPT) significantly (P

Heatstroke is associated with systemic inflammatory response syndrome, leading to multiple organ dysfunction and death. Currently, there is no specific treatment decreasing hyperthermia-induced inflammatory/hemostatic derangements. Emerging studies indicate that histones leaking from damaged cells into the extracellular space are toxic, pro-inflammatory, and pro-thrombotic. We therefore hypothesize that serum histones (sHs) are elevated during heatstroke and are associated with the severity of the disease. Sixteen dogs with heatstroke and seven healthy controls were included in the study. Median serum histones (sHs) upon admission in dogs with heatstroke were significantly higher (P = 0.043) compared to that in seven controls (13.2 vs. 7.3 ng/mL, respectively). sHs level was significantly higher among non-survivors and among dogs with severe hemostatic derangement (P = 0.049, median 21.4 ng/mL vs. median 8.16 ng/mL and P = 0.038, 19.0 vs. 7.0 ng/mL, respectively). There were significant positive correlation between sHs and urea (r = 0.8, P = 0.02); total CO2 (r = 0.661, P = 0.05); CK (r = 0.678, P = 0.04); and prothrombin time (PT) 12 h post presentation (r = 0.888, P = 0.04). The significant positive correlation between sHs and other heatstroke severity biomarkers, and significant increase among severely affected dogs, implies its role in inflammation/oxidation/coagulation during heatstroke. sHs, unlike other prognostic and severity biomarkers in heatstroke, can be pharmacologically manipulated, offering a potential therapeutic target.

Heatstroke is a serious illness in dogs characterized by core temperatures above 41 °C with central nervous system dysfunction. Experimental heatstroke models have tried to correlate biomarker levels with the severity of the syndrome. Serum heat shock protein (eHSP70) levels were recently evaluated as a biomarker of heat tolerance and acclimation, their role as a marker of heatstroke is inconclusive. Here, we monitored eHSP70 levels in correlation with systemic biomarkers in 30 naturally occurring canine heatstroke cases. Thirty dogs diagnosed with environmental (33 %) or exertional (66 %) heatstroke admitted to hospital (0–14 h post-injury) were tested for biomarkers of organ damage and coagulation parameters. eHSP70 levels were measured upon admission and 4, 12, and 24 h later (T1, T2, and T3, respectively). No differences were found between exertional and environmental heatstroke cases. The eHSP profile demonstrated an inverted bell shape, with the lowest levels at the 12 h time point. A positive correlation between eHSP70, lactate, and aPPT was also noted at T2 in all the dogs in the study. Twenty-four h after presentation, eHSP70 levels returned to those measured upon admission, this change was only significant in the survivors. The obtained results suggest that eHSP72 level profile may be predictive of survival.