Efferent Pathways in Sodium Overload-Induced Renal Vasodilation in Rats

Hypernatremia stimulates the secretion of oxytocin (OT), but the physiological role of OT remains unclear. the present study sought to determine the involvement of OT and renal nerves in the renal responses to an intravenous infusion of hypertonic saline. Male Wistar rats (280-350 g) were anesthetized with sodium thiopental (40 mg. kg(-1), i.v.). A bladder cannula was implanted for collection of urine. Animals were also instrumented for measurement of mean arterial pressure (MAP) and renal blood flow (RBF). Renal vascular conductance (RVC) was calculated as the ratio of RBF by MAP. in anesthetized rats (n = 6), OT infusion (0.03 mu g . kg(-1), i.v.) induced renal vasodilation. Consistent with this result, ex vivo experiments demonstrated that OT caused renal artery relaxation. Blockade of OT receptors (OXTR) reduced these responses to OT, indicating a direct effect of this peptide on OXTR on this artery. Hypertonic saline (3 M NaCl, 1.8 ml . kg(-1) b.wt., i.v.) was infused over 60 s. in sham rats (n = 6), hypertonic saline induced renal vasodilation. the OXTR antagonist (AT; atosiban, 40 mu g . kg(-1) . h(-1), i.v.; n = 7) and renal denervation (RX) reduced the renal vasodilation induced by hypernatremia. the combination of atosiban and renal denervation (RX+AT; n = 7) completely abolished the renal vasodilation induced by sodium overload. Intact rats excreted 51% of the injected sodium within 90 min. Natriuresis was slightly blunted by atosiban and renal denervation (42% and 39% of load, respectively), whereas atosiban with renal denervation reduced sodium excretion to 16% of the load. These results suggest that OT and renal nerves are involved in renal vasodilation and natriuresis induced by acute plasma hypernatremia.Fundacao de Amparo a Pesquisa do Estado de Goias (FAPEG)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Univ Fed Goias, Ctr Neurosci & Cardiovasc Physiol, Inst Biol Sci, Dept Physiol Sci, Goiania, Go, BrazilUniv Fed Uberlandia, Fac Phys Educ, Inst Biol Sci, BR-38400 Uberlandia, MG, BrazilUniversidade Federal de São Paulo, Dept Physiol, São Paulo, BrazilUniv Fed Goias, Inst Biol Sci, Mol Biol Lab, Goiania, Go, BrazilUniv Fed Goias, Inst Biol Sci, Dept Biochem & Mol Biol, Goiania, Go, BrazilUniversidade Federal de São Paulo, Dept Physiol, São Paulo, BrazilFundacao de Amparo a Pesquisa do Estado de Goias (FAPEG): 2012/0055431086Fundacao de Amparo a Pesquisa do Estado de Goias (FAPEG): 2009/10267000352CNPq: 477832/2010-5CNPq: 483411/2012-4Web of Scienc

Gene therapy with AR isoform 2 rescues spinal and bulbar muscular atrophy phenotype 2 by modulating AR transcriptional activity:AR isoform 2 counteracts polyglutamine AR toxicity

Spinal and bulbar muscular atrophy (SBMA) is an X-linked, adult-onset neuromuscular condition caused by an abnormal polyglutamine (polyQ) tract expansion in androgen receptor (AR) protein. SBMA is a disease with high unmet clinical need. Recent studies have shown that mutant AR-altered transcriptional activity is key to disease pathogenesis. Restoring the transcriptional dysregulation without affecting other AR critical functions holds great promise for the treatment of SBMA and other AR-related conditions; however, how this targeted approach can be achieved and translated into a clinical application remains to be understood. Here, we characterized the role of AR isoform 2, a naturally occurring variant encoding a truncated AR lacking the polyQ-harboring domain, as a regulatory switch of AR genomic functions in androgen-responsive tissues. Delivery of this isoform using a recombinant adeno-associated virus vector type 9 resulted in amelioration of the disease phenotype in SBMA mice by restoring polyQ AR-dysregulated transcriptional activity

Dystrophin regulates peripheral circadian SRF signalling

Dystrophin is a sarcolemmal protein essential for muscle contraction and maintenance, absence of which leads to the devastating muscle wasting disease Duchenne muscular dystrophy (DMD)[1, 2]. Dystrophin has an actin-binding domain [3–5], which specifically binds and stabilises filamentous (F)-actin[6], an integral component of the RhoA-actin-serum response factor (SRF)-pathway[7]. The RhoA-actin-SRF-pathway plays an essential role in circadian signalling whereby the hypothalamic suprachiasmatic nucleus, transmits systemic cues to peripheral tissues, activating SRF and transcription of clock target genes[8, 9]. Given dystrophin binds F-actin and disturbed SRF-signalling disrupts clock entrainment, we hypothesised that dystrophin loss causes circadian deficits. Here we show for the first time alterations in the RhoA-actin-SRF-signalling-pathway, in both dystrophin-deficient myotubes and dystrophic mouse models. Specifically, we demonstrate reduced F/G-actin ratios and nuclear MRTF, dysregulation of core clock and downstream target-genes, and down-regulation of key circadian genes in muscle biopsies from DMD patients harbouring an array of mutations. Further, disrupted circadian locomotor behaviour was observed in dystrophic mice indicative of disrupted SCN signalling, and indeed dystrophin protein was absent in the SCN of dystrophic animals. Dystrophin is thus a critically important component of the RhoA-actin-SRF-pathway and a novel mediator of circadian signalling in peripheral tissues, loss of which leads to circadian dysregulation

Nucleic acid structures as transcriptional and epigenetic regulators in health and disease

DNA and RNA structures are involved in major biological processes, such as regulating gene expression, and can play an important role in cancer and neurodegenerative diseases. Huntingtonâs disease (HD) is the most common monogenic neurological disorder caused by the expanded and unstable CAG trinucleotide repeat in the first exon of the huntingtin gene (HTT). The pathology of HD has been traditionally associated with the mutant HTT protein, which confers toxic gain of function leading to dysfunction and death of neurons. However, recent evidence indicates that at least part of the gain of function may operate at the RNA level. In the first part of this thesis, the transcriptional and epigenetic regulation of the HTT gene in HD is investigated. It is shown that expanded CAG repeats of endogenous HTT transcript adopt double-stranded RNA structures that lead to RNA Polymerase II transcriptional repression and heterochromatin formation of the HTT gene in cis, providing a molecular link between dsRNA and the pathology of expansion diseases. Double-stranded RNA is a key player in numerous Biological activities in cells, however little is known about the proteins that bind to dsRNA. Therefore, a proteomics approach was established, employing the dsRNA pull-down to identify dsRNA-binding proteins in control and HD fibroblast cells. Analysis of the dsRNA interactome indicated that interaction with the top candidate ENO1 is enriched in HD and promotes dsRNA-mediated transcriptional repression of the HTT gene. This thesis work also elucidates on the importance of RNA/DNA hybrids in cancer as their accumulation is a major cause for genomic instability. The research demonstrated that cancer cells overexpressing oncogenes such as HRASV12, lead to increased RNA synthesis and RNA/DNA hybrid accumulation that can be correlated with replication stress. These events lead to DNA damage, revealing a strong link between R-loop-mediated genome instability and human disease. Overall, nucleic acid structures and their interactors could determine the ability of a single gene product to perform multiple functions, as potential disease modifiers and future targets to modulate diseases.</p

Nucleic acid structures as transcriptional and epigenetic regulators in health and disease

DNA and RNA structures are involved in major biological processes, such as regulating gene expression, and can play an important role in cancer and neurodegenerative diseases. Huntington’s disease (HD) is the most common monogenic neurological disorder caused by the expanded and unstable CAG trinucleotide repeat in the first exon of the huntingtin gene (HTT). The pathology of HD has been traditionally associated with the mutant HTT protein, which confers toxic gain of function leading to dysfunction and death of neurons. However, recent evidence indicates that at least part of the gain of function may operate at the RNA level. In the first part of this thesis, the transcriptional and epigenetic regulation of the HTT gene in HD is investigated. It is shown that expanded CAG repeats of endogenous HTT transcript adopt double-stranded RNA structures that lead to RNA Polymerase II transcriptional repression and heterochromatin formation of the HTT gene in cis, providing a molecular link between dsRNA and the pathology of expansion diseases. Double-stranded RNA is a key player in numerous Biological activities in cells, however little is known about the proteins that bind to dsRNA. Therefore, a proteomics approach was established, employing the dsRNA pull-down to identify dsRNA-binding proteins in control and HD fibroblast cells. Analysis of the dsRNA interactome indicated that interaction with the top candidate ENO1 is enriched in HD and promotes dsRNA-mediated transcriptional repression of the HTT gene. This thesis work also elucidates on the importance of RNA/DNA hybrids in cancer as their accumulation is a major cause for genomic instability. The research demonstrated that cancer cells overexpressing oncogenes such as HRASV12, lead to increased RNA synthesis and RNA/DNA hybrid accumulation that can be correlated with replication stress. These events lead to DNA damage, revealing a strong link between R-loop-mediated genome instability and human disease. Overall, nucleic acid structures and their interactors could determine the ability of a single gene product to perform multiple functions, as potential disease modifiers and future targets to modulate diseases

Bias and standard errors using BLUP and ssGBLUP with different proportions of multiple sires.

<p>Bias and standard errors using BLUP and ssGBLUP with different proportions of multiple sires.</p

Typical tracing of changes in cardiovascular parameters induced by intravenous injection of vehicle (0.1 ml NaCl 150 mmol • l⁻¹) and oxytocin (0.008, 0.016 e 0.03 µg • kg⁻¹ b.wt., i.v.) in anesthetized rats (A).

<p>Effects of oxytocin or vehicle infusion on renal vascular conductance (RVC) in anesthetized rats (B; n = 6). Concentration–response curve for relaxation of the isolated renal artery by oxytocin (0.3×10⁻⁶ to 3×10⁻⁶ M; C - n = 6 rings taken from 5 rats). Error bars indicate S.E.M. Dashed line indicates oxytocin injection. AP = arterial pressure, MAP = mean arterial pressure, RBF = renal blood flow, RVC = renal vascular conductance. *p<0.05 compared to vehicle.</p