Cardiomyocyte troponin T immunoreactivity is modified by crosslinking resulting from intracellular calcium overload

BACKGROUND: During myocardial ischemia, the increase in cytosolic Ca2+ promotes the activation of neutral proteases such as calpains. Since the troponin T subunit is a substrate for calpains, we investigated the effects of irreversible myocyte damage on troponin T immunoreactivity. METHODS AND RESULTS: Hearts from adult guinea pigs (n=32) were perfused under conditions of normoxia, ischemia, postischemic reperfusion, or Ca2+ paradox. Hearts were frozen and processed for immunohistochemistry and Western blot with three anti-troponin T monoclonal antibodies. Two of these antibodies are unreactive on cryosections of freshly isolated and normoxic hearts and of hearts exposed to 30 minutes of no-flow ischemia. In contrast, reactivity is detected in rare myocytes after 60 minutes of ischemia, in a large population of myocytes after 60 minutes of ischemia followed by 30 minutes of reperfusion, and in every myocyte exposed to Ca2+ paradox. In Western blots, samples from ischemia-reperfusion and Ca2+ overloaded hearts show reactive polypeptides of about 240 to 260 kD and 65 to 66 kD in addition to troponin T. A similar pattern of immunoreactivity is observed with an anti-troponin I antibody. Histochemical troponin T immunoreactivity and reactivity on high-molecular-weight polypeptides are detectable in normal heart samples after preincubation with 10 mmol/L Ca2+ or with transglutaminase, whereas they are not if either transglutaminase or calpain is inhibited. CONCLUSIONS: The evolution of the ischemic injury is accompanied by changes in troponin T immunoreactivity as a consequence of the calcium-dependent activation of both calpain proteolysis and transglutaminase cross-linking

Changes in mitochondrial activity caused by ammonium salts and the protective effect of carnitine

Ammonium salts added to isolated rat liver mitochondria deviate alpha-ketoglutarate to glutamate synthesis, thus decreasing its availability as respiratory substrate. As a consequence a decrease of respiratory rate is observed which is paralleled by progressive mitochondrial swelling. It was demonstrated that L-carnitine may abolish this swelling thus improving structural and metabolic state of mitochondria

Dietary intake of cyanidin-3-glucoside induces a long-lasting cardioprotection from ischemia/reperfusion injury by altering the microbiota

The anthocyanin class of flavonoids, including cyanidin-3-glucoside (C3G) present in berries, blood oranges and pigmented cereal crops, are food bioactives with antioxidant and anti-inflammatory action, capable to reduce myocardial ischemia/reperfusion (I/R) injury by unclear mechanism. Assessing the value of sporadic beneficial diet is critical for practical application. We aimed to determine whether and how the cardioptotective effect of dietary intake of anthocyanins persists. Gene expression, histology and resistance to I/R were investigated ex vivo in hearts from mice after a month beyond the cease of the C3G-enriched diet. Cardiac injury, oxidative stress and mitochondrial damage following I/R was effectively reduced in mice fed C3G-enriched diet, even after a month of wash out with standard diet. Cardioprotection was observed also in immune-deficient mice lacking mature B and T cells indicating the anti-inflammatory activity of C3G was not involved. Moreover, the transcription reprogramming induced by the C3G-enriched diets was rescued by the wash out treatment. Instead, we found C3G-enriched diet changed the microbiome and the transplantation of the fecal microbiota transferred the cardioprotection from mice fed C3G-enriched diet to mice fed standard diet. These findings established the effect of C3G dietary intake on gut microbiota determines long lasting cardioprotection

Thomas Devlin. biochimica con aspetti clinico-farmaceutici. Capitolo 25. digestione e assorbimento dei principali nutrienti.

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