Identification and functional separation of retinoic acid receptor neutral antagonists and inverse agonists.

Inverse agonists are ligands that are capable of repressing basal receptor activity in the absence of an agonist. We have designed a series of C-1-substituted acetylenic retinoids that exhibit potent antagonism of retinoic acid receptor (RAR)-mediated transactivation. Comparison of these related retinoid antagonists for their ability to repress basal RAR transcriptional activity demonstrates that the identity of the C-1 substituent differentiates these ligands into two groups: RAR inverse agonists and neutral antagonists. We show that treatment of cultured human keratinocytes with a RAR inverse agonist, but not a RAR neutral antagonist, leads to the repression of the serum-induced differentiation marker MRP-8. While RAR-selective agonists also repress expression of MRP-8, cotreatment with a RAR inverse agonist and a RAR agonist results in a mutual repression of their individual inhibitory activities, indicating the distinct modes of action of these two disparate retinoids in modulating MRP-8 expression. Our data indicate that RARs, like beta2-adrenoreceptors, are sensitive to inverse agonists and that this new class of retinoids will provide insight into the molecular mechanisms of RAR function in skin and other responsive tissues.

Ozone-Induced Alterations in the Accumulation of Newly Synthesized Proteins in Leaves of Maize.

We examined the response of leaves of 3-week-old maize (Zea mays L.) to short-term (5 h) fumigation with O3-enriched air (0, 0.12, 0.24, or 0.36 [mu]L/L). Older leaves and leaf tissue developed more severe visible damage at higher external O3 concentrations. To investigate the immediate effect of O3 exposure on the accumulation of newly synthesized leaf proteins, leaves were labeled with [35S]methionine after 2 h and fumigated for an additional 3 h. O3-induced alterations of leaf proteins were observed in a concentration-dependent manner. There was a significant decrease in [35S]methionine incorporation into protein at the highest O3 concentration. Developmental differences in accumulation of de novo-synthesized leaf proteins were observed when the leaf tip, middle, and basal sections were labeled under 0 [mu]L/L O3, and additional changes were apparent upon exposure to increasing O3 concentrations. Changes in leaf protein synthesis were observed in the absence of visible leaf injury. Subcellular fractionation revealed O3-induced alterations in soluble and membrane-associated proteins. A number of thylakoid membrane-associated proteins showed specific increases in response to O3 fumigation. In contrast, the synthesis of a 32-kD polypeptide associated with thylakoid membranes was reduced in response to O3 fumigation in parallel with reduced incorporation of [35S]methionine into protein. Immunoprecipitation identified this polypeptide as the D1 protein of photosystem II. A reduction in the accumulation of newly synthesized D1 could have consequences for the efficiency of photosynthesis and other cellular processes.

Effects of pindolol and propranolol on blood lipids in hypertensive patients.

Since beta-blockers could affect lipid levels at the therapeutic dose range in hypertensive patients, a parallel 6-month randomized trial with pindolol (PDL) (16 pts.) and propranolol (PPL) (23 pts.) was designed (mean age = 55 + 7.1 years and 57 + 8.0 years; 9 males, 7 females and 15 males, 8 females, respectively). Total cholesterol, LDL and HDL fractions, and triglycerides (TGs) were determined before (washout phase) and during 1, 3, and 6 months of therapy. Patients were instructed to maintain their usual dietary habits. Daily drug doses were adjusted step by step to attain an optimal hypotensive effect (PDL 15-45 mg, PPL 180-240 mg). In the PPL-treated group, total cholesterol and LDL did not change significantly, HDL decreased (from 45.2 to 40.5 mg/dl, p less than 0.05) and TG increased (from 133 to 169 mg/dl, p less than 0.05). In the PDL group total cholesterol and LDL did not change either, but HDL increased (35.9 to 44.7 mg/dl, p less than 0.01) and TGs, were reduced (from 169 to 131 mg/dl, p less than 0.05). No dose-effect relationship was recorded. It is concluded that pindolol does not negatively influence HDL nor the TG blood lipid profile as does PPL. Accordingly, pindolol might be preferred to propranolol in the treatment of hypertensive patients with an unfavorable lipid profile, but this assumption remains to be proven in larger, prospective, long-term followup trials.

Effects of pindolol and clopamide on blood lipids in arterial hypertensive patients.

The effects of clopamide, pindolol and its combination on plasma lipids in 49 hypertensive patients (WHO I-II), divided into three parallel randomized groups, were studied over a 6 months period. Total cholesterol, triglycerides, HDL and LDL cholesterol fractions were determined twice during an initial 4-week washout phase, and after a 1-, 3- and 6-month active hypotensive drug phase. Patients were instructed to maintain their usual dietary habits. Daily drug doses were adjusted progressively to attain optimal hypotensive effects. In the clopamide monotherapy group, total cholesterol increased significantly (p less than 0.05); triglycerides and LDL showed a tendency to increase while for HDL a tendency to decrease was observed. In the pindolol monotherapy group, a significant reduction of triglycerides (p less than 0.01) and a significant increase of HDL cholesterol (p less than 0.05) were recorded. No significant changes in total cholesterol or LDL fraction were observed. Combined pindolol-clopamide therapy decreased total triglycerides (NS), increased HDL significantly (p less than 0.05) and did not influence total cholesterol and LDL fraction. It is concluded that pindolol does not negatively influence blood lipids as the thiazide-type diuretic clopamide does, and that when both drugs are used together, the beta-blocker can probably counterbalance the diuretic-induced negative effects on blood lipids. Accordingly, it is suggested that pindolol could be a more favorable beta-blocker drug to be used on hypertensive subjects with metabolic coronary risk factors.

Glucose tolerance and the insulin response in recently drinking alcoholic patients: possible effects of withdrawal.

To investigate possible effects of withdrawal on carbohydrate metabolism in chronic alcoholic patients, intravenous glucose tolerance tests were performed in three periods in 11 alcoholic patients: early abstinence (less than three days), early abstinence plus ethanol (1 g/kg/BW IV), and late abstinence (three weeks later). According to liver biopsy results and laboratory tests, patients were classified as a group with liver damage (four cases) and a group without it (seven cases). In the group without damage, glucose tolerance expressed as K% and compared to a control group, was significantly decreased in early and late abstinence but not after the infusion of ethanol. Cases with damage also had glucose intolerance at admission. Plasma insulin levels after the glucose load were significantly lower at ten and 30 minutes in the group without damage, in early or late abstinence. They were normal in the presence of ethanol. Patients with liver damage presented higher basal and postglucose plasma insulin concentrations. It was concluded that glucose intolerance in alcoholic patients is a common finding that occurs in the presence or absence of liver damage. In cases with liver damage it seems to be due to peripheral insulin resistance. In those without damage it is related to low peripherovenous insulin levels.

Content of hepatic reduced glutathione in chronic alcoholic patients: influence of the length of abstinence and liver necrosis.

The relationship between the content of hepatic reduced glutathione (GSH) and the length of abstinence was investigated in 45 chronic alcoholic patients. Hepatic GSH levels were significantly correlated (r = 0.58; P less than 0.001) with the length of alcohol withdrawal in the whole group. According to liver histology patients were divided into two groups, with and without hepatic necrosis. Subjects without necrosis showed a significant positive correlation (r = 0.71; P less than 0.001) between GSH values and the length of abstinence; no correlation (r = -0.22; P less than 0.40) was observed in the group with necrosis. According to the period of abstinence patients were separated into two groups, with a short (less than or equal to 5 days) and a prolonged (greater than 5 days) alcohol withdrawal. Patients with and without necrosis exhibited comparable mean levels of liver GSH (2.04 +/- SEM 0.21 and 1.74 +/- 0.23 mumol/g respectively; P less than 0.30) when studied after short periods of abstinence. Alcoholics without liver necrosis showed significantly higher hepatic GSH levels than those with necrosis (3.23 +/- 0.30 and 1.60 +/- 0.33 respectively; P less than 0.01) after prolonged periods of alcohol withdrawal. Similar results were obtained when liver GSH levels were expressed as a function of the mean surface area of hepatocytes, which was not significantly different between patients with and without hepatic necrosis. Parameters assessing the nutritional status of patients with and without necrosis were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)