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Query: UMLS:C0020440 (hypercapnia)
 7,939 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The mammalian carotid body (CB) is a polymodal chemosensor which can detect low blood glucose (hypoglycaemia), leading to increased afferent discharge and activation of counter-regulatory autonomic pathways. The underlying neurotransmitter mechanisms are unknown and controversy surrounds whether the action of low glucose is direct or indirect. To address this, we used a coculture model containing functional chemosensory units of rat CB receptor (type I) cell clusters and afferent petrosal neurones (PN). During perforated-patch, whole-cell recordings, low glucose (0-2 mM) stimulated sensory discharge in cocultured PN. When the background P(O2) was lowered to levels typical of arterial blood (approximately 90 mmHg), robust PN chemoexcitation could be induced by physiological hypoglycaemia (3.3-4 mM glucose). These sensory responses were reversibly inhibited by a combination of purinergic (suramin, 50 microM) and nicotinic (mecamylamine, 1 microM) receptor blockers, suggesting that transmission depended on corelease of ATP and ACh. Hypoglycaemic responses were additive with those evoked by hypoxia or hypercapnia; further, they could be potentiated by the GABAB receptor blocker (CGP 55845) and inhibited by 5-HT2A receptor blockers (ketanserin or ritanserin). During paired simultaneous recordings from a PN and a type I cell in an adjacent cluster, the afferent PN response coincided with type I cell depolarization, which was associated with a decrease in input resistance. In fresh tissue slices of rat CB, low glucose stimulated ATP secretion as determined by the luciferin-luciferase assay; this secretion was cadmium sensitive, potentiated by CGP 55845, and inhibited by ketanserin. Taken together these data indicate that CB receptors act as direct glucosensors, and that processing of hypoglycaemia utilizes similar neurotransmitter and neuromodulatory mechanisms as hypoxia.
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PMID:Neurotransmitter mechanisms mediating low-glucose signalling in cocultures and fresh tissue slices of rat carotid body. 1717 41

Elevated blood and tissue CO(2), or hypercapnia, is common in severe lung disease. Patients with hypercapnia often develop lung infections and have an increased risk of death following pneumonia. To explore whether hypercapnia interferes with host defense, we studied the effects of elevated P(CO2) on macrophage innate immune responses. In differentiated human THP-1 macrophages and human and mouse alveolar macrophages stimulated with lipopolysaccharide (LPS) and other Toll-like receptor ligands, hypercapnia inhibited expression of tumor necrosis factor and interleukin (IL)-6, nuclear factor (NF)-kappaB-dependent cytokines critical for antimicrobial host defense. Inhibition of IL-6 expression by hypercapnia was concentration dependent, rapid, reversible, and independent of extracellular and intracellular acidosis. In contrast, hypercapnia did not down-regulate IL-10 or interferon-beta, which do not require NF-kappaB. Notably, hypercapnia did not affect LPS-induced degradation of IkappaB alpha, nuclear translocation of RelA/p65, or activation of mitogen-activated protein kinases, but it did block IL-6 promoter-driven luciferase activity in mouse RAW 264.7 macrophages. Elevated P(CO2) also decreased phagocytosis of opsonized polystyrene beads and heat-killed bacteria in THP-1 and human alveolar macrophages. By interfering with essential innate immune functions in the macrophage, hypercapnia may cause a previously unrecognized defect in resistance to pulmonary infection in patients with advanced lung disease.
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PMID:Elevated CO2 selectively inhibits interleukin-6 and tumor necrosis factor expression and decreases phagocytosis in the macrophage. 2018 40

Patients with severe lung disease may develop hypercapnia, elevation of the levels of CO2 in the lungs and blood, which is associated with increased risk of death, often from infection. To identify compounds that ameliorate the adverse effects of hypercapnia, we performed a focused screen of 8832 compounds using a CO2-responsive luciferase reporter in Drosophila S2* cells. We found that evoxine, a plant alkaloid, counteracts the CO2-induced transcriptional suppression of antimicrobial peptides in S2* cells. Strikingly, evoxine also inhibits hypercapnic suppression of interleukin-6 and the chemokine CCL2 expression in human THP-1 macrophages. Evoxine's effects are selective, since it does not prevent hypercapnic inhibition of phagocytosis by THP-1 cells or CO2-induced activation of AMPK in rat ATII pulmonary epithelial cells. The results suggest that hypercapnia suppresses innate immune gene expression by definable pathways that are evolutionarily conserved and demonstrate for the first time that specific CO2 effects can be targeted pharmacologically.
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PMID:Focused Screening Identifies Evoxine as a Small Molecule That Counteracts CO2-Induced Immune Suppression. 2670 Oct 99