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Role of phospholipase C and protein kinase C in vasoconstrictor-induced prostaglandin synthesis in cultured rat renal mesangial cells.

ABSTRACT: It was the aim of the present study to find out if a common mechanism exists by which the vasoconstrictive hormones angiotension II, noradrenaline and 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC) increase prostaglandin E2 (PGE2) synthesis in cultures of rat renal mesangial cells. Angiotension II, noradrenaline and AGEPC stimulated PGE2 synthesis and uptake of 45Ca2+ in cultured mesangial cells. Both of these effects could be completely suppressed by the calcium channel blocker verapamil. Angiotensin II, noradrenaline and AGEPC caused a rapid breakdown of phosphatidylinositol 4,5-bisphosphate with a concomitant increase of 1,2-diacylglycerol and inositol trisphosphate, indicating an activation of phospholipase C by these hormones. Addition of verapamil had no effect on the hormone-induced stimulation of phospholipase C. The synthetic analogue of diacylglycerol, 1-oleoyl-2-acetylglycerol, and the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA), both of which are known to stimulate protein kinase C, enhanced PGE2 synthesis. Chelation of extracellular calcium with EDTA or addition of verapamil abolished the effect of 1-oleoyl-2-acetylglycerol and phorbol ester on PGE2 synthesis. 1-Oleoyl-2-acetylglycerol and phorbol ester increased the uptake of 45Ca2+ by the cells in a dose-dependent manner and this effect could be blocked by verapamil. The entirety of these data leads us to suggest that vasoconstrictor-evoked synthesis of PGE2 in rat mesangial cells is mediated by the subsequent activation of phospholipase C and protein kinase C. The activation of protein kinase C by diacylglycerol is likely to be involved in the increase of the calcium permeability of the plasma membrane which is a prerequisite for PGE2 synthesis induced by vasoconstrictive hormones.

SUBMITTER: Pfeilschifter J

PROVIDER: S-EPMC1146534 | biostudies-other | 1986 Feb

REPOSITORIES: biostudies-other

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Project description:ObjectiveIntestinal barrier function is vital for homeostasis. Conditions where the mucosal barrier is compromised lead to increased plasma content of lipopolysaccharide (LPS). LPS acts on Toll-like receptor 4 (TLR4) and initiates cellular inflammatory responses. TLR4 receptors have been identified on enteric neurons and LPS exposure causes neuronal loss, counteracted by vasoactive intestinal peptide (VIP), by unknown mechanisms. In addition AMP activated protein kinase (AMPK) stimulation causes loss of enteric neurons. This study investigated a possible role of AMPK activation in LPS-induced neuronal loss.DesignPrimary cultures of myenteric neurons isolated from rat small intestine were used. Cultures were treated with LPS (0.2-20 µg/mL) with and without TAK1-inhibitor (5Z)-7-Oxozeaenol (10-6 M) or AMPK inhibitor compound C (10-5 M). AMPK-induced neuronal loss was verified treating cultures with three different AMPK activators, AICAR (10-4-3×10-3 M), metformin (0.2-20 µg/mL) and A-769662 (10-5-3×10-4 M) with or without the presence of compound C (10-5 M). Upstream activation of AMPK-induced neuronal loss was tested by treating cultures with AICAR (10-3 M) in the presence of TAK1 inhibitor (5Z)-7-Oxozeaenol (10-6 M). Neuronal survival and relative numbers of neurons immunoreactive (IR) for VIP were evaluated using immunocytochemistry.ResultsLPS caused a concentration dependent loss of neurons. All AMPK activators induced loss of myenteric neurons in a concentration dependent manner. LPS-, AICAR- and metformin-,but not A-769662-, induced neuronal losses were inhibited by presence of compound C. LPS, AICAR or metformin exposure increased the relative number of VIP-IR neurons; co-treatment with (5Z)-7-Oxozeaenol or compound C reversed the relative increase in VIP-IR neurons induced by LPS. (5Z)-7-Oxozeaenol, compound C or A-769662 did not per se change neuronal survival or relative numbers of VIP-IR neurons.ConclusionAMPK activation mimics LPS-induced loss of cultured myenteric neurons and LPS-induced neuronal loss is counteracted by TAK1 and AMPK inhibition. This suggests enteric neuroimmune interactions involving AMPK regulation.

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Role of phospholipase C and protein kinase C in vasoconstrictor-induced prostaglandin synthesis in cultured rat renal mesangial cells.

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