Platonin, a cyanine photosensitizing dye, is effective for attenuation of heatstroke in rats

"Unravelling the impacts of climatic heat events on cardiovascular health in animal models"

Climate change has led to an increase in high ambient temperatures, causing extreme heat events worldwide. According to the World Meteorological Organization (WMO), July 2023 marked a historic milestone as the Earth reached its hottest recorded temperature, precisely hitting the critical threshold of 1.5 °C set by the Paris Agreement. This distressing development led to a stark warning from the United Nations, signaling the dawn of what they call "an era of global boiling". The increasing global temperatures can result in high heat stress which leads to various physiological and biochemical alterations in the human body. Given that cardiovascular diseases (CVDs) are a leading cause of morbidity and mortality globally, heat events exacerbate this public health issue. While clinical and in-vitro studies have suggested a range of pathophysiological and biochemical mechanisms underlying the body's response to heat stress, the complex nature of organ-system level interactions makes precise investigation challenging. To address this knowledge gap effectively, the use of animal models exposed to acute or chronic heat stress can be invaluable. These models can closely replicate the multifaceted effects observed in humans during heat stress conditions. Despite extensive independent reviews, limited focus has been shed on the high heat-induced cardiovascular complications and their mechanisms, particularly utilizing animal models. Therefore, in this comprehensive review, we highlight the crucial biomarkers altered during heat stress, contributing significantly to various CVDs. We explore potential mechanisms underlying heat-induced cardiovascular dysfunction and damage, delving into various animal models. While traditional rodent models are commonly employed, we also examine less conventional models, including ruminants, broilers, canines, and primates. Furthermore, we delve into various potential therapeutic approaches and preventive measures. These insights hold significant promise for the development of more effective clinical interventions against the effects of heat stress on the human cardiovascular system.

Inhibition of tau polymerization with a cyanine dye in two distinct model systems

In a host of neurodegenerative diseases Tau, a microtubule-associated protein, aggregates into insoluble lesions within neurons. Previous studies have utilized cyanine dyes as Tau aggregation inhibitors in vitro. Herein we utilize cyanine dye 3,3'-diethyl-9-methyl-thiacarbocyanine iodide (C11) to modulate Tau polymerization in two model systems, an organotypic slice culture model derived from Tau transgenic mice and a split green fluorescent protein complementation assay in Tau-expressing cells. In slice cultures, submicromolar concentrations (0.001 microm) of C11 produced a significant reduction of aggregated Tau and a corresponding increase in unpolymerized Tau. In contrast, treatment with a 1 microm dose promoted aggregation of Tau. These results were recapitulated in the complementation assay where administration of 1 microm C11 produced a significant increase in polymerized Tau relative to control, whereas treatment of cells with 0.01 microm C11 resulted in a marked reduction of aggregated Tau. In the organotypic slice cultures, modulation of Tau aggregation was independent of changes in phosphorylation at disease and microtubule binding relevant epitopes for both dosing regimes. Furthermore, treatment with 0.001 microm C11 resulted in a decrease in both total filament mass and number. There was no evidence of apoptosis or loss of synaptic integrity at either dose, however, whereas submicromolar concentrations of C11 did not interfere with microtubule binding, higher doses resulted in a decrease in the levels of microtubule-bound Tau. Overall, a cyanine dye can dissociate aggregated Tau in an ex vivo model of tauopathy with little toxicity and exploration of the use of these type of dyes as therapeutic agents is warranted.

Hyperbaric oxygen improves survival in heatstroke rats by reducing multiorgan dysfunction and brain oxidative stress

Hyperbaric oxygen has been found to be beneficial in treating heatstroke animals. We attempted to further assess the possible mechanism of therapeutic protection offered by hyperbaric oxygen in experimental heatstroke. Anesthetized rats, immediately after the onset of heatstroke, were randomized into the following groups and given: a) hyperbaric oxygen (100% O(2) at 253 kPa for 1 h); or b) normal air. They were exposed to 43 degrees C temperature to induce heatstroke. When the untreated rats underwent heat stress, their survival time values were found to be 20-24 min. Resuscitation with hyperbaric oxygen increased the survival time to new values of 152-176 min. All untreated heatstroke rats displayed cerebrovascular dysfunction (evidenced by hypotension, intracranial hypertension, and cerebral hypoperfusion, hypoxia, and ischemia), hypercoagulable state (evidenced by increased levels of activated partial thromboplastin time, prothrombin time, and D-dimer, but decreased values of platelet count and protein C in plasma), and tissue ischemia/injury (evidenced by increased levels of creatinine, serum urea nitrogen, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase in plasma, and dihydrobenzoic acid, lipid peroxidation, and oxidized-form glutathione/reduced-form of glutathione ratio in hypothalamus). The cerebrovascular dysfunctions, hypercoagulable state, tissue ischemia/injury, and brain oxidative stress that occurred during heatstroke were all suppressed by hyperbaric oxygen therapy. The current results indicate that hyperbaric oxygen therapy may resuscitate rats that had a heatstroke by decreasing multiple organ dysfunction and brain oxidative stress.