Altered signal pathway in granulocytes from patients with hypercholesterolemia

Abstract

In the present study the signal transduction of the formyl-Met-Leu-Phe receptor was studied in granulocytes obtained from control subjects and patients with elevated low density lipoprotein levels. According to our results, 10 n M formyl-Met-Leu-Phe in control cells activates phospholipase C inducing a pronounced inositol phosphate production followed by a Ca 2 ؉ signal from intracellular pools. The pertussis toxin-sensitive O 2 ؊ generation and leukotriene synthesis were moderate. In contrast, in granulocytes from hypercholesterolemic patients, formyl-Met-Leu-Phe triggered an intensive pertussis toxin-insensitive oxidative burst and leukotriene synthesis. The inositol trisphosphate and Ca 2 ؉ signals were decreased significantly in granulocytes of hypercholesterolemic patients and seem to be dependent on the extracellular Ca 2 ؉ content. Furthermore, in the resting granulocytes of hypercholesterolemic patients the [Ca 2 ؉ ]i and the membrane-bound protein kinase C activity were higher than in controls, the time of normalization after the low Ca 2 ؉ signal was delayed, while the membrane fluidity was decreased. Our results suggest that in these ex vivo experiments, the high level of circulating low density lipoprotein in patients can affect the membrane composition of granulocytes leading to altered signal transduction by the formyl-Met-Leu-Phe receptor, to altered Ca 2 ؉ pump-activity, and protein kinase C translocation. -

Impact of ursodeoxycholic acid on a CCK1R cholesterol-binding site may contribute to its positive effects in digestive function

“…The obesity connection relates to CCK being a satiety factor, with the vagal afferent CCK1R contributing to the physiological postcibal satiety response (29). The cholesterol connection relates to unique sensitivity of this receptor to membrane cholesterol (13,23,37), with elevated levels of this lipid, as have been observed in obese patients with metabolic syndrome (11,35,42), resulting in reduced biological responses to CCK (23,48,49,52), whereas the closely related CCK2R is insensitive to cholesterol (37). The gallstone connection has largely been recognized in highly unusual kindreds, in which this receptor was found to be misprocessed and defective (32).…”

Mechanism of Action and Structure–Activity Relationships of Tetracyclic Small Molecules Acting as Universal Positive Allosteric Modulators of the Cholecystokinin Receptor

“…Such an agent would be expected to enhance the satiety effect of endogenously released CCK during and after a meal to reduce meal size in a temporally finite manner. There was also the additional benefit that such an agent could reverse the negative impact of elevated membrane cholesterol on stimulus–activity coupling at this receptor [ 27 , 28 ].…”

Discovery of a Positive Allosteric Modulator of Cholecystokinin Action at CCK1R in Normal and Elevated Cholesterol

“…In contrast, a CCK1R PAM with minimal intrinsic agonist activity could provide a safer and more efficacious approach for targeting this receptor by enhancing the temporally finite, and spatially resolved, physiological short duration of action of endogenous CCK released after a meal (7,8). Importantly, PAMs have the potential to correct the aberrant stimulus-activity coupling of CCK action at the CCK1R observed in a high-cholesterol microenvironment, such as exists in some obese patients (34,35). Traditional efforts to develop drugs acting at the CCK1R have focused on the discovery of compounds with high intrinsic efficacy for receptor activation.…”