Expressão e caracterização farmacológica dos subtipos de adrenoceptores α1 na cauda proximal e distal do epidídimo de rato

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Verificação da associação da variabilidade genética da Alfa-1-antitripsina e do fator de necrose tumoral com a asma brônquica

A asma brônquica é uma desordem inflamatória crônica, complexa, na qual estão envolvidos fatores genéticos e ambientais. A inflamação das vias aéreas na asma é regulada, predominantemente, por células do sistema imunológico e por uma vasta rede de citocinas que interagem mutuamente e com as vias aéreas. O exato desempenho funcional de cada citocina na fisiopatologia da asma ainda necessita ser completamente estabelecido. A presente investigação teve como objetivo comparar a distribuição dos alelos S e Z do gene da A1AT e do polimorfismo do gene do TNF-α (-308 G/A) em uma população de 110 asmáticos, divididos em dois níveis de severidade da asma (com 54 pacientes no nível da doença moderada persistente e 56 pacientes no nível da doença severa persistente). Os genótipos da A1AT e do TNF-α (-308 G/A) foram determinados pela técnica de digestão enzimática (polimorfismo no comprimento dos fragmentos de restrição). O polimorfismo no promotor do gene do fator de necrose tumoral TNF-α (-308G/A), citocina pro-inflamatória que participa da reação inflamatória em pacientes com asma, contribuindo para a hiperreatividade brônquica, não foi na presente investigação, associado com a doença ou com o aumento da hiperreatividade brônquica, nos níveis de severidade sintomática mais graves da doença.

Investigação da participação de adrenoceptores α1 no efeito antinociceptivo da amitriptilina em um modelo de dor neuropática

Tricyclic antidepressants, such as amitriptyline, are inhibitors of serotonin and norepinephrine neuronal reuptake and this action has been implied in changes in pain threshold supporting its use to alleviate neuropathic pain. Although is known that 1 adrenoceptors participate in the antinociceptive effect of amitriptyline it is unclear which receptor subtype is the target for the increased synaptic levels of norepinephrine resultant from the inhibition of neuronal uptake. Paradoxically, several tricyclic antidepressants including amitriptyline also behave as antagonists of 1 adrenoceptors with different affinities for its subtypes: these drugs have 10 to 100-fold higher affinities for 1A than for 1B and 1D adrenoceptors. This work investigated the involvement of 1 adrenoceptors subtypes in the antinociceptive effect of the amitriptyline in a constriction of the sciatic nerve in rats by determining the effects of subtype selective 1 adrenoceptors antagonists. Fifteen days later, mechanical hyperalgesia was analyzed in a Randall-Selitto test. The 1A-selective antagonist RS100329 was the most potent antagonist of the contractions of the rat prostate, whereas the 1D-selective antagonist BMY 7378 (up to 100g/Kg) was unable to affect these contractions. The antagonist prazosin, BMY 7378 and 5-methyl urapidil inhibited the antinociceptive effect of the amitriptyline. However, the highly selective 1A adrenoceptor antagonist RS100329 was unable to affect the antinociception induced by amitriptyline. These results point out that 1B and/or 1D adrenoceptors, but not 1A, are involved in the antinociceptive effects of amitriptyline

Investigação do envolvimento de subtipos de adrenoceptores α1 no efeito anti-imobilidade da imipramina no teste de suspensão pela cauda

Pós-graduação em Ciências Biológicas (Farmacologia) - IBB

Mirabegron relaxes urethral smooth muscle by a dual mechanism involving β3-adrenoceptor activation and α1-adrenoceptor blockade

Mirabegron is the first β3-adrenoceptor (AR) agonist approved for treatment of overactive bladder syndrome (OAB). This study aimed to investigate the effects of β3-adrenoceptor (AR) agonist mirabegron in mouse urethra. The possibility that mirabegron exerts α1-AR antagonism was also tested in rat smooth muscle preparations presenting α1A- (vas deferens and prostate), α1D- (aorta) and α1B-AR (spleen). Functional assays were carried out in mouse and rat isolated tissues. Competition assays for the specific binding of [(3) H]Prazosin to membrane preparations of HEK 293 cells expressing each of the human α1-ARs, as well as β-AR mRNA expression and cyclic AMP measurements in mouse urethra were performed. Mirabegron produced concentration-dependent urethral relaxations that were right shifted by the selective β3-AR antagonist L 748,337, but unaffected by β1- and β2-AR antagonists (atenolol and ICI 118,551, respectively). Mirabegron-induced relaxations were enhanced by the phosphodiesterase-4 inhibitor rolipram, and this agonist stimulated cAMP synthesis. Mirabegron also produced rightward shifts in urethral contractions induced by the α1-AR agonist phenylephrine. Schild regression analysis revealed that mirabegron behaves as a competitive antagonist of α1-AR in urethra, vas deferens and prostate (α1A-AR, pA2  ≅ 5.6) and aorta (α1D-AR, pA2  ≅ 5.4), but not in spleen (α1B-AR). The affinities estimated for mirabegron in functional assays were consistent with those estimated in radioligand binding with human recombinant α1A- and α1D-ARs (pKi ≅ 6.0). The effects of mirabegron in urethral smooth muscle are the result of β3-AR agonism together with α1A / α1D-AR antagonism.

Clonidine and phenylephrine injected into the lateral preoptic area reduce water intake in dehydrated rats

In the present study, we investigated the effect of phenylephrine and clonidine (α1- and α2-adrenoceptor agonists, respectively) injected into the lateral preoptic area (LPOA) on the water intake induced by water deprivation in rats. In addition, the effects of prior injections of prazosin and yohimbine (α1- and α2-adrenoceptor antagonists, respectively) into the LPOA on the antidipsogenic action of phenylephrine and clonidine were investigated. After 30 h of water deprivation, the water intake of rats in a control experiment (saline injection) was 10.5 ± 0.8 ml/h. Injection of clonidine (5, 10, 20, and 40 nmol) into the LPOA reduced water intake to 6.3 ± 0.9, 4.9 ± 0.8, 3.6 ± 1.0, and 2.2 ± 0.7 ml/h, respectively. Similar reductions occurred after injection of 80 and 160 nmol phenylephrine into the LPOA (6.2 ± 1.6 and 4.8 ± 1.3 ml/h, respectively). Pretreatment with prazosin (40 nmol) abolished the antidipsogenic action of an 80-nmol dose of phenylephrine (11.3 ± 1.1 ml/h) and reduced the effect of a 20-nmol dose of clonidine (7.4 ± 1.4 ml/h). Yohimbine (20, 40, and 80 nmol), previously injected, produced no significant changes in the effects of either phenylephrine or clonidine. The present results show that phenylephrine and clonidine injected into the LPOA induce an antidipsogenic effect in water-deprived rat. They also suggest an involvement of α1-adrenoceptors in this effect. A possible participation of imidazole receptors in the effect of clonidine should also be taken into account. © 1993.

alpha-6 Integrin Expression in Bovine Spermatogonial Cells Purified by Discontinuous Percoll Density Gradient

The study of spermatogonial stem cells (SSCs) provides a model to better understand adult stem cell biology. Besides the biomedical potential to perform studies of infertility in many species, SSCs hold a promising application at animal transgenesis. Because stem cells are thought to be associated with basement membranes, expression of alpha-6 integrin has been investigated as a marker of type A spermatogonial cells, which are considered SSCs because of their undifferentiated status and self-renewal ability. In this manner, the aim of this study was to isolate type A SSCs from adult bulls by a two-step enzymatic procedure followed by a discontinuous Percoll density gradient purification and verify the expression of alpha-6 integrin by flow cytometry and real-time RT-PCR before and after Percoll purification. Spermatogonial cells were successfully obtained using the two-step enzymatic digestion. An average of 1 x 10(5) viable cells per gram of testis was isolated. However, the discontinuous Percoll did not purify isolated cells regarding alpha-6 integrin expression. Flow cytometry analysis demonstrated no differences in the alpha-6 integrin expression between cell samples before and after Percoll purification (p = 0.5636). The same was observed in the real-time PCR analysis (p > 0.05). In addition to alpha-6 integrin, the expression of GFR alpha-1 and PGP9.5, known bovine SSCs markers, was detected in all samples studied. Considering that Percoll can reduce cell viability, it is possible to conclude that Percoll density gradient is not suitable to purify bovine SSC, according to alpha-6 integrin expression.

beta-ADRENOCEPTORS IN THE MEDIAL AMYGDALOID NUCLEUS MODULATE THE TACHYCARDIAC RESPONSE TO RESTRAINT STRESS IN RATS

In the present study, we investigated the involvement of beta-adrenoceptors in the medial amygdaloid nucleus (MeA) in cardiovascular responses evoked in rats submitted to an acute restraint stress. We first pretreated Wistar rats with the nonselective beta-adrenoceptor antagonist propranolol microinjected bilaterally into the MeA (10, 15, and 20 nmol/100 nL) 10 min before exposure to acute restraint. The pretreatment with propranolol did not affect the blood pressure (BP) increase evoked by restraint. However, it increased the tachycardiac response caused by acute restraint when animals were pretreated with a dose of 15 nmol, without a significant effect on the BP response. This result indicates that beta-adrenoceptors in the MeA have an inhibitory influence on restraint-evoked heart rate (HR) changes. Pretreatment with the selective beta(2)-adrenoceptor antagonist ICI 118,551 (10, 15, and 20 nmol/100 nL) significantly increased the restraint-evoked tachycardiac response after doses of 15 and 20 nmol, an effect that was similar to that observed after the pretreatment with propranolol at a dose of 15 nmol, without a significant effect on the BP response. Pretreatment of the MeA with the selective beta(1)-adrenoceptor antagonist CGP 20712 (10, 15, and 20 nmol/100 nL) caused an opposite effect on the HR response, and a significant decrease in the restraint-evoked tachycardia was observed only after the dose of 20 nmol, without a significant effect on the BP response. Because propranolol is an equipotent antagonist of both beta(1) and beta(2)-adrenoceptors, and opposite effects were observed after the treatment with the higher doses of the selective antagonists ICI 118,551 and CGP 20712, the narrow window in the dose-response to propranolol could be explained by a functional antagonism resulting from the simultaneous inhibition of beta(1) and beta(2)-adrenoceptors by the treatment with propranolol. The present results suggest that beta(2)-adrenoceptors have an inhibitory influence on the restraint-evoked tachycardiac response, whereas beta(1)-adrenoceptors have a facilitatory influence on the restraint-evoked tachycardiac response. (c) 2012 IBRO. Published by Elsevier Ltd. All rights reserved.

Quantitative mRNA analysis of adrenergic receptor subtypes in the intestines of healthy dairy cows and dairy cows with cecal dilatation-dislocation

OBJECTIVE: To investigate the distribution of mRNA coding for 9 adrenoceptor subtypes in the intestines of healthy dairy cows and cows with cecal dilatationdislocation (CDD). SAMPLE POPULATION: Full-thickness specimens of the intestinal wall were obtained from the ileum, cecum, proximal loop of the ascending colon (PLAC), and external loop of the spiral colon (ELSC) of 15 cows with CDD (group 1) and 15 healthy (control) cows (group 2, specimens collected during laparotomy; group 3, specimens collected after slaughter). PROCEDURES: Concentrations of mRNA for 9 adrenoceptor subtypes (alpha(1A), alpha(1B), alpha(1D), alpha(2AD), alpha(2B), alpha(2C), beta(1), beta(2), and beta(3)) were measured by quantitative real-time reverse transcriptase-PCR assay. Results were expressed relative to mRNA expression of a housekeeping gene. RESULTS: Expression of mRNA for alpha(1B)-, alpha(2AD)-, alpha(2B)-, beta(1)-, and beta(2)-adrenoceptors was significantly lower in cows with CDD than in control cows. In the ileum, these receptors all had lower mRNA expression in cows with CDD than in control cows. The same effect was detected in the ELSC for mRNA for alpha(2AD)-, alpha(2B)-, beta(1)-, and beta(2)-adrenoceptors, and in the cecum and PLAC for alpha(2B)- and beta(2)-adrenoceptors. Groups did not differ significantly for alpha(1A)-adrenoceptors. The mRNA expression for alpha(1D)-, alpha(2C)-, and beta(3)-adrenoceptors was extremely low in all groups. CONCLUSIONS AND CLINICAL RELEVANCE: Differences in expression of mRNA coding for adrenoceptors, most pronounced in the ileum and spiral colon, between cows with CDD and control cows support the hypothesis of an implication of adrenergic mechanisms in the pathogenesis of CDD in dairy cows.

Replacement of histidine in position 105 in the alpha(5) subunit by cysteine stimulates zolpidem sensitivity of alpha(5)beta(2)gamma(2) GABA(A) receptors

Zolpidem is a positive allosteric modulator of GABA(A) receptors with sensitivity to subunit composition. While it acts with high affinity and efficacy at GABA(A) receptors containing the alpha(1) subunit, it has a lower affinity to GABA(A) receptors containing alpha(2), alpha(3), or alpha(5) subunits and has a very weak efficacy at receptors containing the alpha(5) subunit. Here, we show that replacing histidine in position 105 in the alpha(5) subunit by cysteine strongly stimulates the effect of zolpidem in receptors containing the alpha(5) subunit. The side chain volume of the amino acid residue in this position does not correlate with the modulation by zolpidem. Interestingly, serine is not able to promote the potentiation by zolpidem. The homologous residues to alpha(5)H105 in alpha(1), alpha(2), and alpha(3) are well-known determinants of the action of classical benzodiazepines. Other studies have shown that replacement of these histidines alpha(1)H101, alpha(2)H101, and alpha(3)H126 by arginine, as naturally present in alpha(4) and alpha(6), leads to benzodiazepine insensitivity of these receptors. Thus, the nature of the amino acid residue in this position is not only crucial for the action of classical benzodiazepines but in alpha(5) containing receptors also for the action of zolpidem.

Immunohistochemical demonstration of interleukin-1 beta induced changes in acute-phase proteins and albumin in rat liver

Interleukin-1 beta is a potent mediator of the acute-phase response. However, the effects of interleukin-1 beta administration on the topic in vivo production of acute-phase proteins and albumin are so far not well understood. Overnight fasted rats were subcutaneously injected with 0.2 mL 0.9% NaCl (control group) or 6.25 micrograms recombinant human interleukin-1 beta, and rectal temperature was measured at intervals up to 48 h. Livers were perfused-fixed in vivo prior to injection (base-line), and at 9, 24, and 48 h following the interleukin-1 beta injection. Fibrinogen, orosomucoid (alpha 1-acid glycoprotein) and albumin were immunostained using a streptavidin-biotin-immunoperoxidase technique. Rectal temperature peaked 5 h after the single interleukin-1 beta injection, and fell gradually to base-line values by 24 h. Prior to injection only a few hepatocytes, randomly scattered throughout the liver lobule, stained positive for fibrinogen and orosomucoid. In contrast, all hepatocytes stained uniformly positive for fibrinogen and orosomucoid 9 h after interleukin-1 beta injection, whereas at 24 h a predominant centrilobular staining pattern occurred. Due to fasting, albumin positive hepatocytes were already reduced at base-line in both groups. Interleukin-1 beta induced a further significant loss of albumin positive cells in the periportal zone (35 +/- 21%) at 9 h when compared with controls (58 +/- 11%, p = 0.037). In conclusion, subcutaneous interleukin-1 beta (probably by stimulation of interleukin-6) strongly induces fibrinogen and orosomucoid expression in rat liver, and suppresses immunohistochemically stainable albumin in a heterogenous way, mainly in the periportal zone.

Reactivity of human natural antibodies to endothelial cells from Galalpha(1,3)Gal-deficient pigs

BACKGROUND: Xenoreactive human natural antibodies (NAb) are predominantly directed against galactose-alpha(1,3)galactose (Gal). Binding of immunoglobulin (Ig) G and IgM NAb activates porcine endothelial cells (pEC) and triggers complement lysis responsible for hyperacute xenograft rejection. In vitro, IgG NAb induce human natural killer (NK) cell-mediated lysis of pEC by antibody-dependent cell-mediated cytotoxicity (ADCC). The present study examined the levels of anti-porcine NAb in a large number of individuals and addressed the functional role of non-Gal anti-porcine NAb. METHODS: Sera from 120 healthy human blood donors were analyzed for the presence of anti-porcine NAb by flow cytometry using porcine red blood cells (pRBC), lymphoblastoid cells (pLCL), and pEC derived from control or Gal-deficient pigs. Xenogeneic complement lysis was measured by flow cytometry using human serum and rabbit complement. ADCC was analyzed by chromium-release assays using human serum and freshly isolated NK cells. RESULTS: Human IgM binding to pRBC was found in 93% and IgG binding in 86% of all samples. Non-Gal NAb comprised 13% of total IgM and 36% of total IgG binding to pEC. NAb/complement-induced lysis and ADCC of Gal-deficient compared to Gal-positive pEC were 21% and 29%, respectively. The majority of anti-Gal and non-Gal IgG NAb were of the IgG2 subclass. CONCLUSIONS: The generation of Gal-deficient pigs has overcome hyperacute anti-Gal-mediated xenograft rejection in nonhuman primates. Non-Gal anti-porcine NAb represent a potentially relevant immunological hurdle in a subgroup of individuals by inducing endothelial damage in xenografts.

Transcriptional regulation of the mouse $\alpha$2(I) collagen gene

The mouse $\alpha$2(I) collagen gene is specifically expressed in a limited number of cell types in the body including fibroblasts and osteoblasts. We had previously shown that a promoter containing the sequences between $-$350 and +54 bp was expressed at low levels in a cell- and tissue-specific fashion in transgenic mice. Further studies suggested that the sequence between $-$315 and $-$284 bp could mediate cell- and tissue-specific expression of reporter genes in cell culture and in transgenic mice. We report here characterization of the proteins binding to this segment and propose a model for the cell-specific expression conferred by this sequence. In this study we also identified a strong enhancer for the mouse $\alpha$2(I) collagen gene located approximately 13.5 to 19.5 kb upstream of the transcriptional start site. This enhancer segment is characterized by the presence of three cell-specific hypersensitive sites and can drive high levels of cell-specific expression of a heterologous 220-bp mouse $\alpha$1(I) collagen promoter. In the course of this study, we identified a novel zinc finger transcription factor (designated murine epithelial zinc finger, mEZF) which was transiently expressed in the mesenchymal cells which give rise to the skeletal primordia and the metanephric kidney during the early stages of embryogenesis. In newborn mice, the mEZF gene is expressed at high levels in differentiated epithelial cells of the skin, oral mucosa, tongue, esophagus, stomach and colon. Chromosomal mapping suggested that the mEZF gene mapped to mouse Chromosome 4 and that the human homolog of mEZF would likely map to human Chromosome 9q31. This region of the human genome contains tumor suppressor genes for basal cell carcinomas of the skin as well as for squamous cell carcinomas of various organs. We cloned and characterized the human homolog of mEZF and mapped its chromosomal position as a first step in determining whether or not this gene plays a role in the development of these tumors. ^

Analysis of the mechanisms that maintain coordinate production of $\alpha$- and $\beta$-tubulin in mammalian cells

Alpha and beta tubulin are essential proteins in all eukaryotic cells. To study how cells maintain coordinate levels of these two interacting proteins, we have used PCR to add a 9 amino acid epitope from influenza hemagglutinin protein onto the carboxyl terminus of $\alpha$1 and $\beta$1-tubulin. The chimeric tubulin genes (HA$\alpha$1 and HA$\beta$1) were transfected into CHO cells and cell lines that stably express each gene were selected. Cells transfected with HA-tubulin do not exhibit any gross changes in growth or morphology. Immunofluorescence analysis demonstrated that HA-tubulins incorporate into both cytoplasmic and spindle microtubules. A quantitative biochemical assay was used to show that HA-tubulins incorporate into microtubules to a normal extent and do not alter the steady state distribution of endogenous tubulin between monomer and polymer pools. Two-dimensional gel analysis of pulse-labeled cells indicated that when HA$\beta$1-tubulin is expressed at high levels, it slightly represses the synthesis of the endogenous $\beta$-tubulin but produces a small increase in the synthesis of $\alpha$-tubulin. Analysis of cells labeled to steady state showed that HA$\beta$1-tubulin accumulates to a similar level as the wild-type gene product, but together these polypeptides produce only a small increase in total tubulin content consistent with the increased synthesis of $\alpha$-tubulin. It thus appears that HA$\beta$1-tubulin successfully competes with endogenous $\beta$-tubulin for heterodimer formation and that free $\beta$-tubulin subunits (endogenous and HA$\beta$1) are selectively degraded to maintain coordinate amounts of $\alpha$- and $\beta$-tubulin. In addition, the increased synthesis of $\alpha$-tubulin suggested the existence of a mechanism to ensure coordinate synthesis of $\alpha$- and $\beta$-tubulin subunits. To analyze whether reciprocal changes in endogenous tubulin synthesis occur when $\alpha$-tubulin is overexpressed, stably transfected CHO cell lines were isolated in which HA$\alpha$1-tubulin represents 50% of the total $\alpha$-tubulin, and its relative abundance can be further increased to 85-90% by treatment with sodium butyrate. In contrast with results obtained using HA$\beta$1-tubulin, transfection of HA$\alpha$1-tubulin decreased the synthesis of endogenous $\alpha$-tubulin to 60% of normal with little or no change in $\beta$-tubulin synthesis. When the transfected cells were treated with sodium butyrate to further increase HA$\beta$1-tubulin production, a larger decrease in the synthesis of endogenous $\alpha$-tubulin (to 30% of normal) was observed. The repression on the synthesis of endogenous $\alpha$-tubulin polypeptide was found to be directly proportional to the expression of HA$\alpha$1-tubulin indicating the existence of an autoregulatory loop, where $\alpha$-tubulin inhibits its own synthesis. To determine whether overproduction of HA$\alpha$1-tubulin affected the transcription, message stability or translation of endogenous $\alpha$-tubulin, the steady state levels of $\alpha$-tubulin mRNA were analyzed by ribonuclease protection assays. The results showed that the steady state level of $\alpha$-tubulin mRNA is not affected by the overexpression of HA$\alpha$1-tubulin, indicating that the repression is translational. The results are compatible with a model in which $\beta$-tubulin synthesis is largely unperturbed by overexpression of other tubulin subunits, and excess $\beta$-tubulin subunits are rapidly degraded to maintain coordinate $\alpha$- and $\beta$-tubulin levels at steady state. In contrast, free $\alpha$-tubulin represses its own synthesis at the translational level, suggesting that its level of production may be controlled by the amount of $\beta$-tubulin available for heterodimer formation. ^

Conserved sequences and cell-specific DNase I hypersensitive sites upstream from the co-ordinately expressed alpha I- and alpha II-globin genes of Xenopus laevis

The globin gene family of Xenopus laevis comprises pairs of closely related genes that are arranged in two clusters, each pair of genes being co-ordinately and stage-specifically expressed. To get information on putative regulatory elements, we compared the DNA sequences and the chromatin conformation 5' to the co-ordinately expressed adult alpha-globin genes. Sequence analysis revealed a relatively conserved region from the cap site up to position -289, and further upstream seven distinct boxes of homology, separated by more diverged sequences or deletions/insertions. The homology boxes comprise 22 to 194 base-pairs showing 78 to 95% homology. Analysis of chromatin conformation showed that DNase I preferentially cuts the upstream region of both genes at similar positions, 5' to the T-A-T-A and the C-C-A-A-T boxes, only in chromatin of adult erythroblasts and erythrocytes, where adult globin genes are expressed, but not in chromatin of adult liver cells or larval erythrocytes, where these genes are silent. This suggests that cell- and stage-specific activation of these genes coincides with specific changes in chromatin conformation within the proximal upstream region. No difference was found in the nucleotide sequence within the DNase I hypersensitive region proximal to the adult alpha 1-globin gene in DNA from embryonic cells, in which this gene is inactive, and adult erythrocytes, expressing this gene.