Chaperoning of the A1-adenosine receptor by endogenous adenosine - an extension of the retaliatory metabolite concept

Cell-permeable orthosteric ligands can assist folding of G protein-coupled receptors in the endoplasmic reticulum (ER); this pharmacochaperoning translates into increased cell surface levels of receptors. Here we used a folding-defective mutant of human A1-adenosine receptor as a sensor to explore whether endogenously produced adenosine can exert a chaperoning effect. This A1-receptor-Y(288)A was retained in the ER of stably transfected human embryonic kidney 293 cells but rapidly reached the plasma membrane in cells incubated with an A1 antagonist. This was phenocopied by raising intracellular adenosine levels with a combination of inhibitors of adenosine kinase, adenosine deaminase, and the equilibrative nucleoside transporter: mature receptors with complex glycosylation accumulated at the cell surface and bound to an A1-selective antagonist with an affinity indistinguishable from the wild-type A1 receptor. The effect of the inhibitor combination was specific, because it did not result in enhanced surface levels of two folding-defective human V2-vasopressin receptor mutants, which were susceptible to pharmacochaperoning by their cognate antagonist. Raising cellular adenosine levels by subjecting cells to hypoxia (5% O2) reproduced chaperoning by the inhibitor combination and enhanced surface expression of A1-receptor-Y(288)A within 1 hour. These findings were recapitulated for the wild-type A1 receptor. Taken together, our observations document that endogenously formed adenosine can chaperone its cognate A1 receptor. This results in a positive feedback loop that has implications for the retaliatory metabolite concept of adenosine action: if chaperoning by intracellular adenosine results in elevated cell surface levels of A1 receptors, these cells will be more susceptible to extracellular adenosine and thus more likely to cope with metabolic distress.

Polyphenol metabolism provides a screening tool for beneficial effects of Onobrychis viciifolia (sainfoin)

Onobrychis viciifolia (sainfoin) is a traditional fodder legume showing multiple benefits for the environment, animal health and productivity but weaker agronomic performance in comparison to other legumes. Benefits can be mainly ascribed to the presence of polyphenols. The polyphenol metabolism in O. viciifolia was studied at the level of gene expression, enzyme activity, polyphenol accumulation and antioxidant activity. A screening of 37 accessions regarding each of these characters showed a huge variability between individual samples. Principal component analysis revealed that flavonols and flavan 3-ols are the most relevant variables for discrimination of the accessions. The determination of the activities of dihydroflavonol 4-reductase and flavonol synthase provides a suitable screening tool for the estimation of the ratio of flavonols to flavan 3-ols and can be used for the selection of samples from those varieties that have a specific optimal ratio of these compounds for further breeding.

[The influence of interleukin-6 and tumor necrosis factor alpha gene polymorphisms on bone mineral density in postmenopausal women]

Proinflammatory cytokines, interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha), involved into osteoclastogenesis and responsible for bone resorption process, participate in the pathogenesis of the osteoporosis. In vitro studies have shown that single nucleotide polymorphisms of IL-6 and TNF-alpha genes could influence the transcription process of the genes and the cytokines level.

AIM

Assessment of the influence of IL-6 and TNF-alpha gene polymorphisms on bone mineral density (BMD) and evaluation of their connection with osteoporosis prevalence in women from Wielkopolska region.

MATERIAL AND METHODS

In the group of 267 postmenopausal women (average age 58.5+/-5.9 years, average age of last period 49.8+/-3.9 years) bone mineral density in lumbar spine (L2-L4) was performed using dual energy X-ray absorptiometry (DXA). Genotypes frequencies were determined by polymerase chain reaction with restriction fragment length polymorphism (PCR/RFLP) using restriction enzymes Lwe I and Faq I, respectively. The connection between the polymorphisms of investigated genes and body mass index, age of menarche and menopause and length of reproductive age had been analyzed as well.

RESULTS

No statistically significant association was found between examined genetic factors and the value of bone mineral density in the investigated group of postmenopausal women. The frequencies of investigated genotypes were in compliance with Hardy-Weinberg equilibrium. The correspondence between evaluated clinical parameters and IL-6 i TNF-alpha genotypes frequencies has not been proven.

CONCLUSIONS

The -174G/C polymorphism in the IL-6 and -308G/A polymorphism in TNF-alpha genes have no influence on bone mineral density value (BMD) in the investigated population of women from Wielkopolska region.

Effect of ramipril vs amlodipine on renal outcomes in hypertensive nephrosclerosis: a randomized controlled trial

CONTEXT

Incidence of end-stage renal disease due to hypertension has increased in recent decades, but the optimal strategy for treatment of hypertension to prevent renal failure is unknown, especially among African Americans.

OBJECTIVE

To compare the effects of an angiotensin-converting enzyme (ACE) inhibitor (ramipril), a dihydropyridine calcium channel blocker (amlodipine), and a beta-blocker (metoprolol) on hypertensive renal disease progression.

DESIGN, SETTING, AND PARTICIPANTS

Interim analysis of a randomized, double-blind, 3 x 2 factorial trial conducted in 1094 African Americans aged 18 to 70 years with hypertensive renal disease (glomerular filtration rate [GFR] of 20-65 mL/min per 1.73 m(2)) enrolled between February 1995 and September 1998. This report compares the ramipril and amlodipine groups following discontinuation of the amlodipine intervention in September 2000.

INTERVENTIONS

Participants were randomly assigned to receive amlodipine, 5 to 10 mg/d (n = 217), ramipril, 2.5 to 10 mg/d (n = 436), or metoprolol, 50 to 200 mg/d (n = 441), with other agents added to achieve 1 of 2 blood pressure goals.

MAIN OUTCOME MEASURES

The primary outcome measure was the rate of change in GFR; the main secondary outcome was a composite index of the clinical end points of reduction in GFR of more than 50% or 25 mL/min per 1.73 m(2), end-stage renal disease, or death.

RESULTS

Among participants with a urinary protein to creatinine ratio of >0.22 (corresponding approximately to proteinuria of more than 300 mg/d), the ramipril group had a 36% (2.02 [SE, 0.74] mL/min per 1.73 m(2)/y) slower mean decline in GFR over 3 years (P =.006) and a 48% reduced risk of the clinical end points vs the amlodipine group (95% confidence interval [CI], 20%-66%). In the entire cohort, there was no significant difference in mean GFR decline from baseline to 3 years between treatment groups (P =.38). However, compared with the amlodipine group, after adjustment for baseline covariates the ramipril group had a 38% reduced risk of clinical end points (95% CI, 13%-56%), a 36% slower mean decline in GFR after 3 months (P =.002), and less proteinuria (P<.001).

CONCLUSION

Ramipril, compared with amlodipine, retards renal disease progression in patients with hypertensive renal disease and proteinuria and may offer benefit to patients without proteinuria.

The diagnosis of interstitial cystitis revisited: lessons learned from the National Institutes of Health Interstitial Cystitis Database study

PURPOSE

The lack of a precise working definition of interstitial cystitis may have resulted in the de facto use of the National Institute of Diabetes, Digestive and Kidney Diseases (NIDDK) "research" definition by clinicians. We evaluated these strict criteria in light of the broader inclusion criteria for patients evaluated in the Interstitial Cystitis Database study to determine their utility in clinical practice as a useful basis for the diagnosis of interstitial cystitis.

MATERIALS AND METHODS

A total of 379 women who completed screening for the Interstitial Cystitis Database before January 1, 1996 met the basic criteria of urinary frequency, urgency or pain for at least 6 months in duration without a diagnosable etiology. Of these patients 148 underwent cystoscopy and hydrodistention of the bladder as a part of the evaluation. All patients were followed for a minimum of 1 year. Comparisons were made between patients judged to have a clinical diagnosis of interstitial cystitis and those who met the NIDDK research definition of the syndrome.

RESULTS

Almost 90% of patients potentially meeting NIDDK criteria are believed by experienced clinicians to have interstitial cystitis, confirming the research value of these criteria in defining a homogeneous population for study. However, strict application of NIDDK criteria would have misdiagnosed more than 60% of patients regarded by researchers as definitely or likely to have interstitial cystitis.

CONCLUSIONS

The NIDDK criteria are too restrictive to be used by clinicians as the diagnostic definition of interstitial cystitis.

Lessons from the Hemodialysis (HEMO) Study: an improved measure of the actual hemodialysis dose

The Hemodialysis (HEMO) Study is a multicenter, prospective, randomized, 2 x 2 factorial clinical trial designed to evaluate the efficacy of the dose of dialysis delivered ("standard" v "high") and dialysis membrane flux ("low" v "high") in reducing the morbidity and mortality of patients. The study is nearly half complete. Although both patients and investigators are blinded to the overall findings, which will not be available for another 3 years, important data have been generated from which a more accurate expression has been derived for the dose of dialysis received by each patient in the trial. This new expression of the effectiveness of dialysis, eKt/V, is a two-pool approximation derived from the traditional single-pool Kt/V (spKt/V) and time on dialysis. The dialysis prescription for the HEMO Study subjects is individualized to achieve the target dose for each patient and is closely monitored by measuring the more accurate and validated expression of eKt/N. Comparisons of the HEMO Study dose of dialysis with other studies have been confused by this unique expression (eKt/V) of the dialysis dose and adequacy adopted for the HEMO Study. The target eKt/V dose in the "standard" arm of the Study is 1.05 and in the "high" arm is 1.45 per dialysis thrice weekly. Based on data available from 426 subjects randomized to each arm, the target of 1.05 in the "standard" dose of the HEMO Study is equivalent to an spKt/V of 1.32, and that of the "high" dose, 1.67. Thus, volunteers in the "standard" arm of the Study are receiving a tightly controlled and closely monitored dose, which is above the current national mean spKt/V, and above that of the accepted minimum standard spKt/N of 1.2. When completed, the HEMO Study will show whether there are merits of a tightly controlled hemodialysis dose that is consistently delivered over a prolonged period and whether a high dose is beneficial and safe to prescribe.

The influence of parenteral nutrition on the course of acute renal failure

The influence of hypertonic glucose with and without added amino acids was studied in 129 consecutive postoperative patients with acute renal failure. The addition of amino acids was associated with lower mortality and morbidity rates in the patients who received dialysis as well as in those who did not. There was no significant differences in the blood urea nitrogen levels of the two groups. The incidence of hyperkalemia and the rise in plasma osmolality were less in the group given adequate calories and amino acids.