Effects of acute and chronic ethanol on cyclic AMP accumulation in NG108‐15 cells: differential dependence of changes on extracellular adenosine

Abstract

1 This study investigated the effects of acute and chronic ethanol on basal, agonist-and forskolinstimulated cyclic AMP formation in NG108-15 mouse neuroblastoma x rat glioma hybrid cells, and examined the role of changes in extracellular adenosine concentrations on the effects observed. 2 NG108-15 cells incubated acutely with ethanol (1-200 mM) displayed concentration-dependent increases in basal and iloprost-stimulated (300nM; a prostanoid IP receptor agonist) cyclic AMP accumulation but a concentration-dependent decrease in forskolin-stimulated (10LM) accumulation. 3 Cells treated chronically with ethanol (200 mM) for 48 h displayed increases over control in basal, iloprost-(0.001-10 LM) and forskolin (0.01-100 gM)-stimulated cyclic AMP formation. However, chronic ethanol did not affect [3H]-iloprost binding to cell membranes. 4 Inclusion of adenosine deaminase (ADA; 1 unit ml-1) during the incubation period to measure cyclic AMP accumulation completely abolished the increase in basal accumulation following chronic ethanol, but did not affect the increase in iloprost stimulation. On the other hand ADA partially reversed the increase in forskolin stimulation following chronic ethanol, but even in the presence of high concentrations of ADA (5 units ml-') the forskolin stimulation remained elevated above control. 5 Cells treated chronically with the adenosine receptor agonist 5'-(N-ethylcarboxamido)-adenosine (NECA; 10 tLM for 48 h) displayed a reduction in subsequent NECA-and forskolin-stimulated cyclic AMP accumulation, but iloprost stimulation was not affected. ADA included acutely during the incubation period to measure cyclic AMP accumulation abolished the reduction in forskolin but not NECA stimulation produced by the chronic NECA pretreatment. 6 We have previously noted that ethanol inhibits NG108-15 cell proliferation and alters cell morphology. To mimic this, cells were incubated in the absence of foetal calf serum for 48 h. Following this time, basal, iloprost-and forskolin-stimulated cyclic AMP formation was enhanced over that in cells grown in the presence of serum. 7 These results indicate that chronic ethanol enhances cyclic AMP formation in intact NG108-15 cells by more than one mechanism: one involves increased extracellular adenosine concentrations and the other a change in the transduction system beyond the receptor, possibly involving the adenylyl cyclase enzyme. Furthermore the ethanol-induced changes in cyclic AMP accumulation may relate to alterations in NG108-15 cell growth and development.

Activation in vitro of vitellogenin uptake by the oocytes of the mosquito, Aedes aegypti

“…The effects of acute exposure on intact cells are more variable, but often increase cAMP production (e.g. Gordon et al, 1986;Hoffman & Tabakoff, 1990;Rabin et al, 1993;Nagy, 1994;Kelly et al, 1995). Thus, the effect of ethanol on mosquito oocytes is consistent with the idea that adenylate cyclase activation is involved in initiating the first phase of vitellogenin uptake.…”

Contractile Responses to Allergen and Cholinergic Stimulation in Bronchus and Trachea of Cockroach Allergen-Sensitized Guinea Pigs

“…The antigen-specific contraction of airway smooth muscles to CRa challenge in vitro is basically similar to the other antigen-specific responses found in other asthma models [24, 26, 27, 28]. This fact, together with findings of asthma-like bronchospasms in vivo in the anesthetized [17] as well as in the conscious state [18], is an additional confirmation that the guinea pigs chronically immunized by simple exposure to airborne CRa have characteristics closely resembling those of human cockroach asthma.…”

MAP kinase signaling in diverse effects of ethanol

“…G-proteins coupled to different second messenger systems are affected by ethanol. In neuroblastoma cells, acute doses of ethanol activated adenylate cyclase, whereas in cells chronically treated with ethanol, adenylate cyclase and G-protein coupled PLC activation were inhibited (Kelly et al, 1995). Ethanol potentiation of p42/44 MAPK activation by serum or PMA in embryonic BNLCL2 liver cells and ethanol potentiation of angiotensin II stimulated p42/44 MAPK activation in primary cultured hepatocytes, both were suppressed by pertussis toxin treatments (Reddy and Shukla, 1996;Weng and Shukla, 2000a).…”