Relaxin down-regulates renal fibroblast function and promotes matrix remodelling in vitro.

BACKGROUND: Renal fibroblasts are important effector cells in tubulointerstitial fibrosis, with experimental antifibrotic strategies focusing on the functional down-regulation of these cells. Several experimental models of fibrosis have provided evidence for the effectiveness of the polypeptide hormone relaxin as a potential antifibrotic agent. This study was conducted to further elucidate the antifibrotic mechanisms of relaxin on renal fibroblasts in vitro. METHODS: Rat cortical fibroblasts were obtained from outgrowth culture of renal tissue isolated from kidneys 3 days post-unilateral ureteric obstruction and constituted 100% of cells studied. A relaxin radio-receptor assay was used to establish binding of relaxin to renal fibroblasts in vitro. Functional studies then examined the effects of H2 relaxin (0, 1, 10 and 100 ng/ml) on fibroblast kinetics, expression of alpha-smooth muscle actin (alpha-SMA), total collagen synthesis, collagenase production and collagen-I lattice contraction. CTGF mRNA expression was also measured by northern analysis. RESULTS: H2 relaxin bound with high affinity to rat renal fibroblasts, but receptor numbers were low. Consistent with its previously reported bimodal effect, transforming growth factor (TGF-beta 1) reduced fibroblast proliferation, an effect abrogated by H2 relaxin. Fibroblasts exposed to H2 relaxin (100 ng/ml) for 24 h demonstrated decreased immunostaining for alpha-SMA and reduced alpha-SMA protein expression compared with controls. There was a trend for a relaxin-mediated reduction in total collagen synthesis and alpha 1(I) mRNA expression with large dose-related increases in collagenase protein expression being observed. TGF-beta 1-stimulated collagen-I lattice contraction was significantly inhibited following co-incubation with 100 ng/ml relaxin. Incremental doses of H2 relaxin had no significant effect on CTGF mRNA expression. CONCLUSIONS: The findings of this study suggest that the antifibrotic effects of relaxin involve down-regulation of fibroblast activity, increase in collagenase synthesis and restructuring of collagen-I lattices, which are consistent with its known physiological role of matrix remodelling. Although there appears to be an interaction between TGF-beta 1 and H2 relaxin, this does not appear to involve a reduction in CTGF mRNA expression.     

Splice variants of the relaxin and INSL3 receptors reveal unanticipated molecular complexity

LGR7 and LGR8 are G protein-coupled receptors that belong to the leucine-rich repeat-containing G-protein coupled receptor (LGR) family, including the thyroid-stimulating hormone (TSH), LH and FSH receptors. LGR7 and LGR8 stimulate cAMP production upon binding of the cognate ligands, relaxin and insulin-like peptide 3 (INSL3), respectively. We cloned several novel splice variants of both LGR7 and LGR8 and analysed the function of four variants. LGR7.1 is a truncated receptor, including only the N-terminal region of the receptor and two leucine rich repeats. In contrast, LGR7.2, LGR7.10 and LGR 8.1 all contain an intact seven transmembrane domain and most of the extracellular region, lacking only one or two exons in the ectodomain. Our analysis demonstrates that although LGR7.10 and LGR8.1 are expressed at the cell surface, LGR7.2 is predominantly retained within cells and LGR7.1 is partially secreted. mRNA expression analysis revealed that several variants are co-expressed in various tissues. None of these variants were able to stimulate cAMP production following relaxin or INSL3 treatment. Unexpectedly, we did not detect any direct specific relaxin or INSL3 binding on any of the splice variants. The large number of receptor splice variants identified suggests an unforeseen complexity in the physiology of this novel hormone-receptor system.     

Serum relaxin and the major endometrial secretory proteins in in-vitro fertilization and down-regulated hormone-supported and natural cycle frozen embryo transfer

Relaxin has been postulated to be a modulator of the expressionof the endometrial secretory proteins, insulin-like growth factorbinding protein (IGFBP-1) and placental protein 14(PP14). Thisstudy evaluated the expression of relaxin in relation to concentrationsof these secretory proteins along with oestradiol, progesteroneand human chorionic gonadotrophin in groups of pregnant andnon-pregnant patients who underwent differing assisted conceptiontreatments. Serum samples were taken from 88 patients at 8 and12 days after embryo transfer. At 12 days after embryo transfer,relaxin concentrations in the pregnant patients who had undergonein-vitro fertilization (IVF) or natural cycle frozen embryotransfer were significantly higher than those who did not conceivein these groups (mean concentrations 8334 versus 28 and 2608versus 62 pg/ml respectively, P <0.001). However concentrationsin the pregnant patients who had hormone support and transferof frozen embryos were not significantly different from thepatients who did not conceive after the same treatment. Althoughrelaxin expression was associated with corpus luteum activity,it was not related to the number of corpora lutea in IVF patients.A wide range of relaxin concentrations was seen to be compatiblewith a healthy pregnancy. These serum relaxin concentrationswere not found to be directly related to the serum concentrationsof IGFBP-1, PP14 or the other factors assessed in this study.     

The Pharmacokinetics of Recombinant Human Relaxin in Nonpregnant Women After Intravenous,Intravaginal, and Intracervical Administration

The pharmacokinetics of recombinant human relaxin (rhRlx) after intravenous (iv) bolus administration and the absorption of rhRlx after intracervical or intravaginal administration were determined in nonpregnant women. The study was conducted in two parts. In part I, 25 women received 0.01 mg/kg rhRlx iv. After a minimum 7-day washout period, these women were dosed intracervically (n = 10) or intravaginally (n = 15) with 0.75 or 1.5 mg rhRlx, respectively, in 3% methylcellulose gel. Part II was a double-blind, randomized, three-way crossover study in 26 women. At 1-month intervals, each woman received one of three intravaginal treatments consisting of 0 (placebo), 1, or 6 mg rhRlx in 3% methylcellulose gel. The serum concentrations of relaxin following iv administration were described as the sum of three exponentials. The mean (±SD) initial, intermediate, and terminal half-lives were 0.09 ± 0.04, 0.72 ± 0.11, and 4.6 ± 1.2 hr, respectively. Most of the area under the curve was associated with the intermediate half-life. The weight-normalized clearance was 170 ± 50 mL/hr/kg. The observed peak concentration was 98 ± 29 ng/mL, and the weight-normalized initial volume of distribution was 78 ± 40 mL/kg, which is approximately equivalent to the serum volume. If central compartment elimination was assumed, the volume of distribution at steady state (V _ss/W) was 280 ± 100 mL/kg, which is approximately equivalent to extracellular fluid volume. V _ss/W could be as large as 1300 ± 400 mL/kg without this assumption. After intravaginal administration of the placebo gel, endogenous relaxin concentrations were evident (i.e., 20 pg/mL) in 9 of the 26 women (maximum concentrations, 23–234 pg/mL). A similar proportion of women (approximately 35–40%) exhibited measurable serum concentrations of relaxin following intravaginal rhRlx treatment; this proportion increased to 90% following intracervical rhRlx treatment. For both routes of administration, the maximum serum concentrations of relaxin were usually within the range of values observed for endogenous relaxin, suggesting that the absorption of rhRlx was minimal.     

The Pharmacokinetics and Metabolism of Human Relaxins in Rhesus Monkeys

Two forms of chemically synthesized human relaxin (hRlx and hRlx-2) were administered as 88 µg/kg intravenous bolus doses to pregnant and nonpregnant rhesus monkeys. No significant differences in pharmacokinetics were observed between pregnant and nonpregnant animals for either form of relaxin; however, clearance of hRlx (3.1–3.4 ml/min/kg) was significantly slower than clearance of hRlx-2 (6.2–6.5 ml/min/kg) in both pregnant and nonpregnant animals. Although the terminal half-lives for hRlx and hRlx-2 were similar (148–157 min), the initial and steady-state volumes of distribution were somewhat larger for hRlx-2 (71–85 and 398–418 ml/kg, respectively) than for hRlx (61–65 and 294–319 ml/kg, respectively). The metabolism of hRlx-2 was also investigated in pregnant and non-pregnant rhesus monkeys after iv bolus (0.44 mg/kg) or 60-min infusion (1.1 mg/kg) administration. Fast atom bombardment mass spectral analysis of the relaxin immunoreactivity isolated from the plasma indicated that hRlx-2 was partially degraded by removal of amino acids from the C terminus of the B chain. The percentage of intact material declined over a 60-min time course. At 60 min post-dose, intact hRlx-2 was 46–64% of the detected material. Degraded forms representing loss of one and four amino acids (hRlx) from the C terminus of the B chain were 11–13 and 19–34% of the detectable material, respectively.     

Relaxin‐3 innervation of the intergeniculate leaflet of the rat thalamus – neuronal tract‐tracing and in vitro electrophysiological studies

Behavioural state is controlled by a range of neural systems that are sensitive to internal and external stimuli. The relaxin‐3 and relaxin family peptide receptor 3 (RXFP3) system has emerged as a putative ascending arousal network with putative involvement in regulation of stress responses, neuroendocrine control, feeding and metabolism, circadian activity and cognition. Relaxin‐3/γ‐aminobutyric acid neuron populations have been identified in the nucleus incertus, pontine raphe nucleus, periaqueductal grey (PAG) and an area dorsal to the substantia nigra. Relaxin‐3‐positive fibres/terminals densely innervate arousal‐related structures in the brainstem, hypothalamus and limbic forebrain, but the functional significance of the heterogeneous relaxin‐3 neuron distribution and its inputs to specific brain areas are unclear. Therefore, in this study, we used neuronal tract‐tracing and immunofluorescence staining to explore the source of the dense relaxin‐3 innervation of the intergeniculate leaflet (IGL) of the thalamus, a component of the neural circadian timing system. Confocal microscopy analysis revealed that relaxin‐3‐positive neurons retrogradely labelled from the IGL were predominantly present in the PAG and these neurons expressed corticotropin‐releasing factor receptor‐like immunoreactivity. Subsequently, whole‐cell patch‐clamp recordings revealed heterogeneous effects of RXFP3 activation in the IGL by the RXFP3 agonist, relaxin‐3 B‐chain/insulin‐like peptide‐5 A‐chain (R3/I5). Identified, neuropeptide Y‐positive IGL neurons, known to influence suprachiasmatic nucleus activity, were excited by R3/I5, whereas neurons of unidentified neurotransmitter content were either depolarized or displayed a decrease in action potential firing and/or membrane potential hyperpolarization. Our data identify a PAG to IGL relaxin‐3/RXFP3 pathway that might convey stress‐related information to key elements of the circadian system and influence behavioural state rhythmicity.     

The Florey turns 50

The origins of the Howard Florey Laboratories of Experimental Physiology, Department of Physiology, The University of Melbourne, are tied to the ground‐breaking clinical work of Derek A Denton in 1947 and to the investigations of the initial scientific team into the control of salt and water balance in health and disease over the period 1947–1963 were Professor RD Wright, Drs JR Goding, IR McDonald, John P Coghlan, E Marelyn Wintour and John R Blair‐West. An Act of Parliament in 1971 by the Victorian State Government formally established the Institute named after Howard Florey, the Australian Nobel Prize winner who isolated penicillin. The Howard Florey Laboratories/Institute quickly became an international leader in the scientific areas of the physiological control of body fluids and electrolyte balance, especially sodium regulation and the regulation of the secretion of aldosterone, the adrenal salt‐retaining hormone; the micro measurement of hormones, in particular steroids and peptides; instinctive ingestive behaviour; fetal fluid regulation; hybridization histochemistry, and the hormone relaxin. Subsequently, the senior staff included, inter alia, Bruce Scoggins, Richard Weisinger, John McDougall, Brian Oldfield, Michael McKinley, Robin McAllen, Hugh Niall, Geoff Tregear and Felix Beck. During the 1990s, an explosion occurred in neuroscience and, in 1997, the Board made the strategic decision to change the focus of the Institute to brain disorders. From 1997 to 2007, Fred Mendelsohn steered the Florey to become one of Australia's premier brain research institutes and, under the current director (the eminent clinician and neuroscientist Geoffrey Donnan), this reputation has been further enhanced.     

松弛素保护心肌微血管内皮细胞缺氧复氧损伤的机制

背景：研究报道松弛素可显著改善病理因素导致的心肾功能障碍,抑制心肌肥厚、抗纤维化以及改善缺血再灌注损伤等,但其对内皮细胞缺氧复氧损伤的保护机制尚不明确。目的：探讨松弛素保护心肌微血管内皮细胞缺氧复氧损伤的机制。方法：取生长状态良好的小鼠心肌微血管内皮细胞系(H5V),分3组处理：对照组常规培养33 h,模型组常规培养24 h后给予6 h缺氧+3 h复氧模拟心肌缺氧再灌注损伤,松弛素组常规培养(加180 ng/mL松弛素)24 h后给予6 h缺氧+3 h复氧(加180 ng/mL松弛素)模拟心肌缺氧再灌注损伤。检测细胞通透性与Caspase-3的表达,细胞上清中肿瘤坏死因子α、白细胞介素1β和白细胞介素6水平,RT-PCR检测细胞中钙黏蛋白、Akt1、GSK-3β mRNA表达;Western blot检测细胞中钙黏蛋白、Akt、GSK-3β蛋白表达。结果与结论：(1)与对照组比较,模型组细胞通透性增强(P <0.05),细胞内Caspase-3表达升高(P <0.05);与模型组比较,松弛素组细胞通透性降低(P <0.05),细胞内Caspase-3表达降低(P &l...     

子痫前期患者血浆CF6、6-Keto-PGF1α和RLX测定的意义

目的：探讨血浆CF6、6-Keto-PGF1α、RLX浓度的改变在子痫前期发生、发展中的作用及测定的临床意义。方法：血浆CF6、6-Keto-PGF1α、RLX三项血管活性物质均采用放射免疫分析。结果：血浆CF6水平轻度子痫前期组显著高于正常孕妇组（P〈0.05）;重度子痫前期组较正常孕妇组CF6水平则升高更为显著（P〈0.01）。6-Keto-PGF1α水平轻度子痫前期组较正常孕妇组（对照组）略微降低（P〉0.05）,重度子痫前期组含量则降低非常显著（P〈0.01）。RLX水平则呈现轻度子痫前期组和重度子痫前期组均显著地低于对照组（P均〈0.01）。重度子痫前期组血浆CF6与6-Keto-PGF1α水平相关性分析示,两者呈显著负相关（r=-0.058,P〈0.05）;与RLX水平亦呈显著负相关（r=-0.611,P〈0.01）。结论：结果证实,CF6、6-Keto-PGF1α、RLX三项血管活性物质水平的变化有助于了解子痫前期的发生机制及临床的预后评估。     

松弛素对高糖环境心脏成纤维细胞胶原基因表达的影响

目的探讨人重组松弛素（rhRLX）对高糖环境大鼠心脏成纤维细胞胶原基因表达的影响。方法原代培养Sprague-Dawley大鼠心脏成纤维细胞。用RT-PCR方法分别观察在正常糖（NG,5.6mmol/L）和高糖（HG,25mmol/L）环境下二代成纤维细胞胶原基因和松弛素基因的表达;rhRLX（100μg/L）分别与NG,HG共同作用72h后成纤维细胞胶原基因的表达。结果HG促进Ⅰ型前胶原mRNA和Ⅲ型前胶原mRNA的表达,rhRLX可以抑制上述作用。HG组松弛素基因的表达比较明显。结论rhRLX对HG促进的Ⅰ型和Ⅲ型胶原基因的表达具有抑制作用。