Activation of bitter taste receptors in pulmonary nociceptors sensitizes TRPV1 channels through the PLC and PKC signaling pathway.

Bitter taste receptors (T2Rs), a G protein-coupled receptor family capable of detecting numerous bitter-tasting compounds, have recently been shown to be expressed and play diverse roles in many extraoral tissues. Here we report the functional expression of T2Rs in rat pulmonary sensory neurons. In anesthetized spontaneously breathing rats, intratracheal instillation of T2R agonist chloroquine (10 mM, 0.1 ml) significantly augmented chemoreflexes evoked by right-atrial injection of capsaicin, a specific activator for transient receptor potential vanilloid receptor 1 (TRPV1), whereas intravenous infusion of chloroquine failed to significantly affect capsaicin-evoked reflexes. In patch-clamp recordings with isolated rat vagal pulmonary sensory neurons, pretreatment with chloroquine (1-1,000 µM, 90 s) concentration dependently potentiated capsaicin-induced TRPV1-mediated inward currents. Preincubating with diphenitol and denatonium (1 mM, 90 s), two other T2R activators, also enhanced capsaicin currents in these neurons but to a lesser extent. The sensitizing effect of chloroquine was effectively prevented by the phospholipase C inhibitor U73122 (1 µM) or by the protein kinase C inhibitor chelerythrine (10 µM). In summary, our study showed that activation of T2Rs augments capsaicin-evoked TRPV1 responses in rat pulmonary nociceptors through the phospholipase C and protein kinase C signaling pathway.

Forget the phosphorus: A case of hypervitaminosis D-induced symptomatic hypercalcemia.

Hypercalcemia is a frequently encountered electrolyte abnormality with a well-described differential diagnosis and classic algorithm for evaluation. The treatment for hypercalcemia is dependent on the underlying etiology. Hypervitaminosis D is an uncommon cause of hypercalcemia, but the use of vitamin D supplementation has expanded and case reports of supplemental vitamin D induced hypercalcemia have become more frequent. We present a case of hypervitaminosis D-induced altered mental status where diagnosis was delayed and additional invasive testing was performed due to an assumption regarding phosphatemia.

A Case of Acute Thrombotic Myocardial Infarction in Polyarteritis Nodosa.

This is a case of a 33-year-old male with acute myocardial infarction from complete thrombotic occlusion of the distal left anterior descending and 1st obtuse marginal artery secondary to polyarteritis nodosa. This case highlights the treatment course and need for continued awareness of vasculitis as a cause for myocardial infarction.