Expression of alpha1-adrenoceptor subtype mRNA as a predictor of the efficacy of subtype selective alpha1-adrenoceptor antagonists in the management of benign prostatic hyperplasia.

PURPOSE: We examined the correlation between the expression of alpha1-adrenoceptor subtype mRNA in the prostate and the clinical efficacy of subtype selective alpha1-adrenoceptor antagonists. We discuss the possibility of individualizing drug therapy in patients with benign prostatic hyperplasia. MATERIALS AND METHODS: A total of 33 patients randomized to the tamsulosin group and 28 randomized to the naftopidil group were enrolled in this study. Each group of patients was administered 0.2 mg tamsulosin hydrochloride or 50 mg naftopidil daily for 12 weeks. Four prostate needle biopsy specimens were obtained from the transition zone to examine the expression of alpha-adrenoceptor subtypes. Specimens were stored at -80 C until used for TaqMan quantitative reverse transcriptase-polymerase chain reaction, which was performed after 12 weeks of treatment. RESULTS: Based on the results of quantitative reverse transcriptase-polymerase chain reaction the tamsulosin and naftopidil groups were grouped into alpha1a-adrenoceptor dominant (22 and 12 patients) and alpha1d-adrenoceptor dominant (11 and 16, respectively) subgroups. The efficacy of tamsulosin hydrochloride and naftopidil differed depending on the dominant expression of the alpha1-adrenoceptor subtype in the prostate. Tamsulosin hydrochloride was more effective in patients with dominant expression of the alpha1a-adrenoceptor subtype, whereas naftopidil was more effective in those with dominant expression of the alpha1d-adrenoceptor subtype. CONCLUSIONS: The expression level of alpha1-adrenoceptor subtype mRNA in the prostate could be a predictor of the efficacy of subtype selective alpha1-adrenoceptor antagonists in patients with benign prostatic hyperplasia. This result implies that genetic differences are responsible for the diverse responses to these drugs.

Change of expression levels of alpha1-adrenoceptor subtypes by administration of alpha1d-adrenoceptor-subtype-selective antagonist naftopidil in benign prostate hyperplasia patients.

BACKGROUND: We examined whether the change of alpha(1)-adrenoceptor (alpha(1)-AR) subtype expression levels in the prostate occurred by administration of the alpha(1d)-AR-subtype-selective antagonist naftopidil to benign prostate hyperplasia (BPH) patients, and discussed the possible alternation of its effectiveness by the chronic administration of alpha(1)-AR antagonists. METHODS: Fifteen patients with untreated BPH aged 58-76 (mean age, 68.2 +/- 7.4 years) underwent prostate biopsy from the transition zone before and after 50 mg naftopidil administration daily for 12 weeks. Taqman quantitative reverse transcription polymerase chain reaction was performed using these biopsy specimens to estimate the expression level of each alpha(1)-AR subtype. Comparison was made of the expression level of alpha(1)-AR subtypes before and after naftopidil administration. We also examined the correlation between the change of alpha(1)-AR subtype expression levels and the short-term efficacy of naftopidil. RESULTS: Naftopidil administration for 12 weeks down-regulated the expression of alpha(1a)-AR and alpha(1b)-AR mRNA and up-regulated the expression of alpha(1d)-AR mRNA without a change in the total alpha(1)-AR mRNA expression level. There was no correlation between the change of alpha(1)-AR subtype expression levels and the short-term efficacy of naftopidil for BPH patients. CONCLUSION: The change of alpha(1d)-AR expression level may be regarded as a compensatory adaptation to chronic alpha(1d)-AR antagonist naftopidil administration. This may mean that long-term use of the same alpha(1)-AR antagonist for BPH patients induces therapeutic tolerance.

Quantification of alpha1-adrenoceptor subtypes by real-time RT-PCR and correlation with age and prostate volume in benign prostatic hyperplasia patients.

BACKGROUND: We used a real-time reverse transcriptase polymerase chain reaction (RT-PCR) method for quantification of each alpha(1)-adrenoceptor (alpha(1)-AR) subtype expression level, and examined whether age and prostate volume influence human prostate alpha(1)-AR subtype expression. METHODS: Enrolled in our study were 75 men with lower urinary tract symptoms (LUTS) secondary to untreated benign prostatic hyperplasia (BPH). Real-time RT-PCR was performed using prostate biopsy specimens to quantify the expression level of each alpha(1)-AR subtype. RESULTS: The median expression level (interquartile range) was 1.24 (0.66-2.32), 0.16 (0.10-0.33), and 1.11 (0.75-2.27) x 1,000 copies/beta-actin for alpha(1a)-, alpha(1b)-, and alpha(1d)-AR mRNA, respectively. The expression levels differed with the individual. The expression levels of alpha(1a)-AR, alpha(1d)-AR, and total alpha(1)-AR mRNA showed a significant positive correlation with patient age, but did not correlate with prostate volume. CONCLUSION: The difference in the expression of the alpha(1)-AR subtype with the patient may be the cause of the difference in the effectiveness of several subtype-selective alpha(1)-AR antagonists from patient to patient. The increase of alpha(1)-AR mRNA expression level with age could be an important factor in the pathogenesis of clinically significant BPH.

Two alpha1-adrenergic receptor subtypes regulating the vasopressor response have differential roles in blood pressure regulation.

To study the functional role of individual alpha1-adrenergic (AR) subtypes in blood pressure (BP) regulation, we used mice lacking the alpha1B-AR and/or alpha1D-AR with the same genetic background and further studied their hemodynamic and vasoconstrictive responses. Both the alpha1D-AR knockout and alpha1B-/alpha1D-AR double knockout mice, but not the alpha1B-AR knockout mice, had significantly (p < 0.05) lower levels of basal systolic and mean arterial BP than wild-type mice in nonanesthetized condition, and they showed no significant change in heart rate or in cardiac function, as assessed by echocardiogram. All mutants showed a significantly (p < 0.05) reduced catecholamine-induced pressor and vasoconstriction responses. It is noteworthy that the infusion of norepinephrine did not elicit any pressor response at all in alpha1B-/alpha1D-AR double knockout mice. In an attempt to further examine alpha1-AR subtype, which is involved in the genesis or maintenance of hypertension, BP after salt loading was monitored by tail-cuff readings and confirmed at the endpoint by direct intra-arterial recording. After salt loading, alpha1B-AR knockout mice developed a comparable level of hypertension to wild-type mice, whereas mice lacking alpha1D-AR had significantly (p < 0.05) attenuated BP and lower levels of circulating catecholamines. Our data indicated that alpha1B- and alpha1D-AR subtypes participate cooperatively in BP regulation; however, the deletion of the functional alpha1D-AR, not alpha1B-AR, leads to an antihypertensive effect. The study shows differential contributions of alpha1B- and alpha1D-ARs in BP regulation.

Responses to noxious stimuli in mice lacking alpha(1d)-adrenergic receptors.

Nociceptive behaviors were examined in the mice lacking alpha1d-adrenergic receptor (alpha1d-AR) and wild type littermates using tail-flick, hot-plate (hindpaw-licking and jumping), tail-pinch and formalin tests. The distribution of alpha1d-AR was studied using in situ hybridization in the wild type mice. Mutant mice showed longer tail-flick and hindpaw-licking latencies while their jumping latency was shorter. Mechanical and chemical nociception was not altered in alpha1d-knockout mice. In situ hybridization study revealed dense alpha1d-AR mRNA expression in the reticular thalamic nucleus, the hippocampus, the cingulate cortex and the spinal cord. These results suggest that alpha1d-AR in the spinal cord contributes to thermal pronociception; and that the jump behavior seen when escaping from heat is inhibited via the supraspinal alpha1d-AR.

alpha 1-Adrenergic receptor subtypes differentially control the cell cycle of transfected CHO cells through a cAMP-dependent mechanism involving p27Kip1.

Three distinct subtypes of alpha(1)-adrenergic receptors (alpha(1)A-, alpha(1)B-, and alpha(1)D-AR) play a prominent role in cell growth. However, little is known about subtype-specific effects on cell proliferation. The activation of alpha(1)A- or alpha(1)B-AR inhibits serum-promoted cell proliferation, whereas alpha(1)D-AR activation does not show such an inhibitory effect. Notably, cell-cycle progression was blocked at G(1)/S transition after activation of alpha(1)A/alpha(1)B-AR but not of alpha(1)D-AR. In agreement with the differential cell proliferation effect, cAMP production was increased after activation of alpha(1)A/alpha(1)B-AR but not alpha(1)D-AR, whereas all alpha(1)-AR subtypes are associated with inositol 1,4,5-trisphosphate production and mitogen-activated protein kinase activation in a similar fashion. Furthermore, the serum-induced reduction in the levels of the cyclin-dependent kinase inhibitor, p27(Kip1), was blocked after activation of alpha(1)A/alpha(1)B-AR but not alpha(1)D-AR. These results show that alpha(1)-AR subtypes differentially activate the cAMP/p27(Kip1) pathway and thereby have differential inhibitory effects on cell proliferation. Subtype-dependent effects should be taken into consideration when assessing the physiological response of native cells where alpha(1)-AR subtypes are generally co-expressed.

Key amino acids for differential coupling of alpha1-adrenergic receptor subtypes to Gs.

We have established that differing effects of alpha1-adrenergic receptor (AR) subtypes on cell proliferation are due to differential coupling to the Gs/cAMP pathway; thus, both alpha1A- and alpha1B-ARs couple to Gs, while alpha1D-AR does not. To identify the region responsible for this difference in subtype-specific Gs coupling, we constructed a series of chimeric and a set of point-mutated human alpha1A- and alpha1D-ARs, and examined their signaling ability. Here, we show that the amino acid residues Thr 136 and Val138 in the intracellular loop II of the human alpha1A-AR are intimately involved with Gs coupling.

Antagonistic effects of antimuscarinic drugs on alpha 1-adrenoceptors.

We previously observed that noradrenaline (NA)-induced contraction of the portal vein of rabbit was relaxed by the antimuscarinic drugs of atropine sulfate, but not scopolamine hydrobromide. In the present study we examined the possible effect of the antimuscarinic drugs of atropine sulfate, scopolamine hydrobromide, p-fluoro-hexa-hydro-sila-difenidol ( p-F-HHSiD, the M(3)-receptor antagonist) and pirenzepine (the M(1)-receptor antagonist) on alpha(1)-adrenoceptor (AR). Atropine and p-F-HHSiD relaxed the alpha(1)-AR agonist methoxamine-induced contraction of the rabbit portal vein in a concentration-dependent manner; however, scopolamine and pirenzepine had no such inhibitory effect. Radioligand binding studies with the alpha(1)-AR ligand 2-[2-(4-hydroxy-3-[(125)I]iodo-phenyl)ethylaminomethyl]-alpha-tetralone ([(125)I]HEAT) in membrane preparations from mouse whole brain showed that atropine (p K(i)=5.33) and p-F-HHSiD (p K(i)=5.88) had higher affinities than scopolamine (p K(i)=3.17) and pirenzepine (p K(i)<2.70). Furthermore, atropine and p-F-HHSiD had higher affinities for all human cloned alpha(1)-ARs than scopolamine and pirenzepine. The results show that the antimuscarinic drugs atropine and p-F-HHSiD have a direct but weak antagonistic activity against alpha(1)-ARs.

The alpha(1D)-adrenergic receptor directly regulates arterial blood pressure via vasoconstriction.

To investigate the physiological role of the alpha(1D)-adrenergic receptor (alpha(1D)-AR) subtype, we created mice lacking the alpha(1D)-AR (alpha(1D)(-/-)) by gene targeting and characterized their cardiovascular function. In alpha(1D)-/- mice, the RT-PCR did not detect any transcript of the alpha(1D)-AR in any tissue examined, and there was no apparent upregulation of other alpha(1)-AR subtypes. Radioligand binding studies showed that alpha(1)-AR binding capacity in the aorta was lost, while that in the heart was unaltered in alpha(1D)-/- mice. Non-anesthetized alpha(1D)-/- mice maintained significantly lower basal systolic and mean arterial blood pressure conditions, relative to wild-type mice, and they showed no significant change in heart rate or in cardiac function, as assessed by echocardiogram. Besides hypotension, the pressor responses to phenylephrine and norepinephrine were decreased by 30-40% in alpha(1D)-/- mice. Furthermore, the contractile response of the aorta and the pressor response of isolated perfused mesenteric arterial beds to alpha(1)-AR stimulation were markedly reduced in alpha(1D)-/- mice. We conclude that the alpha(1D)-AR participates directly in sympathetic regulation of systemic blood pressure by vasoconstriction.