Adrenomedullin mediates early phase angiogenesis induced diabetic nephropathy in STZ diabetic rats.

OBJECTIVE: The implication of pro-angiogenic factors including vascular endothelial growth factor (VEGF) and its receptor flk-1 has been reported in diabetic nephropathy as early event. Adrenomedullin (AM), a potent vasodilator peptide, enhances angiogenesis and high levels were seen in diabetic animals and humans. However, its exact role in diabetic nephropathy is unclear. The present study investigated the effects of adrenomedullin receptor antagonist (ADM-52-22) on the early phase angiogenesis-induced diabetic nephropathy. MATERIALS AND METHODS: 28 male Wistar rats were divided into: 1) Control non-diabetic, 2) Streptozotocin (STZ)-induced diabetic rats (55 mg/kg, i.p.), 3) Control non-diabetic+ADM-52-22, and 4) STZ-diabetes+ADM-52-22 (7 per group). ADM-52-22 was infused for two weeks (250 µg/rat/day, i.p.). RESULTS: Diabetes caused an increase in kidney weight, renal VEGF levels, 24 hr urinary protein and nitric oxide excretion and hyperfiltration indicated by creatinine clearance (CrCl). ADM-22-52 reduced the rise in CrCl, total urinary protein and renal hypertrophy in diabetic rats, and attenuated early angiogenic response to diabetes: CD31 staining, flk1 protein and VEGF renal levels. CONCLUSIONS: These results show that AM through its receptor mediates early angiogenesis-induced diabetic nephropathy which attributes to the early changes as hyperfiltration and hypertrophy.

Possible role of adrenomedullin in the pathogenesis of tubal ectopic pregnancy.

CONTEXT: Tubal ectopic pregnancy (tEP) is currently the leading cause of pregnancy-related deaths during the first trimester. Our current knowledge on the molecular pathogenesis is limited. OBJECTIVE: The objective of the study was to find out the possible role of adrenomedullin (ADM) in the pathogenesis of tEP. DESIGN: This was an experimental in vitro study on oviductal tissue. SETTING: The study was conducted at a university teaching hospital. PATIENTS AND INTERVENTIONS: Patients included those having oviducts removed surgically during salpingectomy for tEP or hysterectomy for benign gynecological conditions. Oviductal tissues were incubated in hormonal condition mimicking early pregnancy before used for in vitro experiments. MAIN OUTCOME MEASURES: Plasma ADM concentration, oviductal expression of ADM and its receptors, ciliary beat frequency, smooth muscle contraction were measured. RESULTS: The ciliary beat frequency and frequency of muscle contraction were lower in the oviducts from patients with tEP than those from simulated normal pregnancy. The plasma and oviductal tissue ADM levels were also lower. The decreases in ciliary beat and frequency of contraction were restored to normal after ADM treatment. CONCLUSIONS: The results suggest that the lower ADM level in the oviducts of tEP may lead to the decrease in ciliary beating and muscle contraction, with the result that the embryo is retained and implanted in the oviduct. Our findings explain for the first time the etiology of tubal pregnancy on the basis of an impairment of the transport of the fertilized ovum resulting from an ADM deficiency and raise the possibility of using the plasma ADM level as a predictor for tubal ectopic pregnancy.

AM1-receptor-dependent protection by intermedin of human vascular and cardiac non-vascular cells from ischaemia-reperfusion injury.

Intermedin (IMD) protects rodent heart and vasculature from oxidative stress and ischaemia. Less is known about distribution of IMD and its receptors and the potential for similar protection in man. Expression of IMD and receptor components were studied in human aortic endothelium cells (HAECs), smooth muscle cells (HASMCs), cardiac microvascular endothelium cells (HMVECs) and fibroblasts (v-HCFs). Receptor subtype involvement in protection by IMD against injury by hydrogen peroxide (H2O2, 1 mmol l⁻¹) and simulated ischaemia and reperfusion were investigated using receptor component-specific siRNAs. IMD and CRLR, RAMP1, RAMP2 and RAMP3 were expressed in all cell types.When cells were treated with 1 nmol l⁻¹ IMD during exposure to 1 mmol l⁻¹ H2O2 for 4 h, viability was greater vs. H2O2 alone (P<0.05 for all cell types). Viabilities under 6 h simulated ischaemia differed (P<0.05) in the absence and presence of 1 nmol l⁻¹ IMD: HAECs 63% and 85%; HMVECs 51% and 68%; v-HCFs 42% and 96%. IMD 1 nmol l⁻¹ present throughout ischaemia (3 h) and reperfusion (1 h) attenuated injury (P<0.05): viabilities were 95%, 74% and 82% for HAECs, HMVECs and v-HCFs, respectively, relative to those in the absence of IMD (62%, 35%, 32%, respectively). When IMD 1 nmol l⁻¹ was present during reperfusion only, protection was still evident (P<0.05, 79%, 55%, 48%, respectively). Cytoskeletal disruption and protein carbonyl formation followed similar patterns. Pre-treatment (4 days) of HAECs with CRLR or RAMP2, but not RAMP1 or RAMP3, siRNAs abolished protection by IMD (1 nmol l⁻¹) against ischaemia-reperfusion injury. IMD protects human vascular and cardiac non-vascular cells from oxidative stress and ischaemia-reperfusion,predominantly via AM1 receptors.

Blockade of adrenomedullin receptors reverses morphine tolerance and its neurochemical mechanisms.

Adrenomedullin (AM) has been demonstrated to be involved in the development of opioid tolerance. The present study further investigated the role of AM in the maintenance of morphine tolerance, morphine-associated hyperalgesia and its cellular mechanisms. Intrathecal (i.t.) injection of morphine for 6 days induced a decline of its analgesic effect and hyperalgesia. Acute administration of the AM receptor antagonist AM(22-52) resumed the potency of morphine in a dose-dependent manner (12, 35.8 and 71.5 µg, i.t.). The AM(22-52) treatment also suppressed morphine tolerance-associated hyperalgesia. Furthermore, i.t. administration of AM(22-52) at a dose of 35.8 µg reversed the morphine induced-enhancement of nNOS (neuronal nitric oxide synthase) and CGRP immunoreactivity in the spinal dorsal horn and/or dorsal root ganglia (DRG). Interestingly, chronic administration of morphine reduced the expression of the endogenous opioid peptide bovine adrenal medulla 22 (BAM22) in small- and medium-sized neurons in DRG and this reduction was partially reversed by the administration of AM(22-52) (35.8 µg). These results suggest that the activation of AM receptors was involved in the maintenance of morphine tolerance mediating by not only upregulation of the pronociceptive mediators, nNOS and CGRP but also the down-regulation of pain-inhibiting molecule BAM22. Our data support the hypothesis that the level of both pronociceptive mediators and endogenous pain-inhibiting molecules has an impact on the potency of morphine analgesia. Targeting AM receptors is a promising approach to maintain the potency of morphine analgesia during chronic use of this drug.