Biochemistry and Pharmacology - Research Publications
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ItemAnnexin-A1 deficiency exacerbates pathological remodelling of the mesenteric vasculature in insulin-resistant, but not insulin-deficient, mice(Wiley, 2020-04)Background and purpose Arterial stiffness, a characteristic feature of diabetes, increases the risk of cardiovascular complications. Potential mechanisms that promote arterial stiffness in diabetes include oxidative stress, glycation and inflammation. The anti‐inflammatory protein annexin‐A1 has cardioprotective properties, particularly in the context of ischaemia. However, the role of endogenous annexin‐A1 in the vasculature in both normal physiology and pathophysiology remains largely unknown. Hence, this study investigated the role of endogenous annexin‐A1 in diabetes‐induced remodelling of mouse mesenteric vasculature. Experimental approach Insulin‐resistance was induced in male mice (AnxA1+/+ and AnxA1‐/‐) with the combination of streptozotocin (55mg/kg i.p. x 3 days) with high fat diet (42% energy from fat) or citrate vehicle with normal chow diet (20‐weeks). Insulin‐deficiency was induced in a separate cohort of mice using a higher total streptozocin dose (55mg/kg i.p. x 5 days) on chow diet (16‐weeks). At study endpoint, mesenteric artery passive mechanics were assessed by pressure myography. Key results Insulin‐resistance induced significant outward remodelling but had no impact on passive stiffness. Interestingly, vascular stiffness was significantly increased in AnxA1‐/‐ mice when subjected to insulin‐resistance. In contrast, insulin‐deficiency induced outward remodelling and increased volume compliance in mesenteric arteries, regardless of genotype. In addition, the annexin‐A1 / formyl peptide receptor axis is upregulated in both insulin‐resistant and insulin‐deficient mice. Conclusion and implications Our study provided the first evidence that endogenous AnxA1 may play an important vasoprotective role in the context of insulin‐resistance. AnxA1‐based therapies may provide additional benefits over traditional anti‐inflammatory strategies for reducing vascular injury in diabetes.
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ItemNo Preview AvailableDifferential expression of mesotocin receptors in the uterus and ovary of the pregnant tammar wallaby(BIO SCIENTIFICA LTD, 2005-05)Mesotocin, an oxytocin-like peptide, is released in highest concentrations during parturition in macropodid marsupials. In late pregnant wallabies, uterine sensitivity to mesotocin increases markedly in the myometrium of the gravid uterus. This coincides with a significant increase in myometrial mesotocin receptor concentrations 3-4 days before term. To date, there is no information on mesotocin receptor gene expression in female wallaby reproductive tissues. This study aimed to examine mesotocin receptor gene expression in the uterus and ovaries of pregnant tammar wallabies, and to localise mesotocin receptors within the uterus. An RT-PCR strategy produced a consensus nucleotide sequence of 834 bp, which encoded 278 amino acids of transmembrane domains I to VI. This protein sequence has approximately 80% homology with the bovine and rat oxytocin receptor exon 2 region. Only one mesotocin receptor was detected in the tammar genome. The myometrium and mammary gland both expressed a 4.1 kb mesotocin receptor gene transcript. Myometrial mesotocin receptor gene expression increased on day 22 of the 26-day gestation and was significantly higher in the gravid than the non-gravid uterus in late pregnancy. This pattern of mesotocin receptor gene expression paralleled mesotocin receptor concentrations. Mesotocin binding sites were localised only to the myometrium, the highest densities being observed in the gravid uterus. Finally, this study showed high expression of mesotocin receptors in the corpus luteum. The pattern of luteal mesotocin receptor expression differed from the myometrium, with a decrease in mesotocin receptors occurring on the day of expected births.
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ItemNo Preview AvailablePurification and characterization of relaxin from the tammar wallaby (Macropus eugenii):: Bioactivity and expression in the corpus luteum(SOC STUDY REPRODUCTION, 2002-07)The objective of this study was to isolate and purify prorelaxin or mature relaxin from the tammar wallaby corpus luteum (CL), determine their structure and bioactivity, and test the hypothesis that enzymatic cleavage of prorelaxin occurs in late gestation. Tammar relaxin peptides were extracted from pooled corpora lutea of late pregnant tammars using a combination of HPLC methods, and they were identified using Western blotting with a human (H2) relaxin antisera and matrix-assisted laser desorption ionization time of flight mass spectrometry. Although no prorelaxin was identified, multiple 6-kDa peptides were detected, which corresponded to the predicted mature tammar relaxin amino acid sequence, with an A chain of 24 amino acids, and different B chain lengths of 28, 29, 30, and 32 amino acids. Tammar relaxin bound with high affinity to rat cortical relaxin receptors and stimulated cAMP production in the human monocytic cell line, THP-1, which expresses the relaxin receptor. Analysis of individual CL indicated that equivalent amounts of mature relaxin peptides were present throughout gestation and also in unmated tammars at equivalent stages of the luteal phase in the nonpregnant cycle. Immunoreactive relaxin was localized specifically to the luteal cells of the CL and the intensity of immunostaining did not vary between gestational stages. These data show that the CL of both pregnant and unmated tammar wallabies produces mature relaxin and suggests that relaxin expression in this species is not influenced by the conceptus. Moreover, the presence of mature relaxin throughout gestation implies that prohormone cleavage is not limited to the later stages of pregnancy
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ItemNo Preview AvailableUp-regulation of mesotocin receptors in the tammar wallaby myometrium is pregnancy-specific and independent of estrogen(OXFORD UNIV PRESS INC, 2002-05)The oxytocin-like peptide of most Australian marsupials is mesotocin, which stimulates uterine contractions and is important for normal birth in the tammar wallaby. Female marsupials have two uteri and, in monovular species such as the tammar, one uterus is gravid with a single fetus, whereas the contralateral uterus is nongravid. A significant increase in myometrial mesotocin receptor concentrations occurs only in the gravid uterus on Day 23 of the 26-day gestation. This study examined whether or not mesotocin receptors are present in the myometrium and are up-regulated at the equivalent stage of the luteal phase in unmated tammars. In contrast to the marked increase in mesotocin receptor mRNA and protein concentrations in the myometrium of the gravid uterus during pregnancy, receptors did not increase in the unmated animals. There were also no significant differences between the two uteri, except on Day 27. Plasma profiles of peripheral estradiol-17beta and progesterone did not differ significantly between pregnant and nonpregnant cycles. However, progesterone concentrations were significantly lower on Day 1 postpartum compared with Day 27 of the nonpregnant cycle. In pregnant tammars, the molar ratio of circulating estradiol-17beta to progesterone increased significantly between Day 25 of gestation and 1 day postpartum, but was not correlated with an increase in mesotocin receptor concentrations in either uterus. The data confirm that a local fetal influence is more important than systemic factors, such as estrogen, in the regulation of uterine mesotocin receptors in the tammar wallaby.