Calcitonin gene-related peptide (CGRP) is a major neurotransmitter and CGRP-containing primary sensory neurons play an important role in nociception and potent vasodilation. CGRP-containing nerves in mesenteric arteries are decreased in pathological animal models (hypertension, diabetes, and atherosclerosis). In apolipoprotein E–knockout mice, which have atherosclerosis and peripheral sensory nerve defects, nerve growth factor (NGF)-mediated CGRP nerve facilitation was down-regulated, which may have been caused by the impairment of the Akt–NO–cGMP pathway. In addition, NGF-mediated CGRP neurite outgrowth was decreased in fructose-induced insulin-resistant rats. We recently discovered that renin–angiotensin inhibitors improved CGRP innervation in spontaneously hypertensive rats, indicating that rescuing CGRP nerve innervation might improve pathophysiological conditions. To find a novel reagent that facilitates CGRP nerves, a new model, phenol-injured perivascular nerve model rats, was established. Adrenomedullin, hepatocyte growth factor, and angiotensin II type 2 receptor activation induced CGRP nerve distribution in phenol-injured rats. Furthermore, in insulin-resistant model rats, the down-regulation of CGRP nerves was likely due to the depression of phosphoinositide 3-kinase (PI3K)-dependent Akt activation. Administration of candesartan improves CGRPergic function via the PI3K–Akt pathway in insulin-resistant rats. Thus, clarification of the mechanisms of CGRP nerve defects may constitute future therapeutic targets.

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Up-regulation of kidney α₂-adrenoceptor expression has been implicated in the development of hypertension in spontaneously hypertensive rats (SHR). This study was carried out to evaluate renal sodium excretion in response to clonidine administration in SHR and control normotensive Wistar-Kyoto (WKY) rats. SHR and WKY rats (12-week-old) were placed in metabolic cages for 4 days: the first 2 days in control conditions and the following 2 days under oral clonidine treatment (100 μg/kg body weight). Clonidine produced a similar reduction in systolic blood pressure values in SHR and WKY rats, although SHR remained hypertensive. At the end of the study SHR and WKY rats presented similar noradrenaline plasma levels. However, noradrenaline kidney tissue levels were significantly higher in SHR compared to WKY rats. Under control conditions, SHR presented lower urine flow compared to WKY rats. Clonidine produced a significant decrease in urine flow in WKY rats but not in SHR. Furthermore, clonidine also produced a significant reduction in urinary sodium, potassium, and creatinine excretion in WKY rats, but had no effect in SHR. In conclusion, in SHR the reduction in systolic blood pressure and sympathetic activity produced by clonidine was not accompanied by a decrease in urine volume and sodium excretion.

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We hypothesized that aliskiren provides renoprotection in diabetic animals that did not receive sufficient renoprotection by AT₁-receptor antagonist treatment. Type 2 diabetic KKAy mice were treated with group 1: vehicle or group 2: valsartan (15 mg/kg per day) from 12 to 16 weeks of age. The mice were subsequently divided into 4 groups and treated with the following combinations of drugs for another 6 weeks: 1: group 1 kept receiving vehicle, 2: group 2 continuously received 15 mg/kg per day of valsartan (Val-Val15), 3: group 2 received 50 mg/kg per day of valsartan (Val-Val50), 4: group 2 continuously received 15 mg/kg per day of valsartan with 25 mg/kg per day of aliskiren (Val-Val+Ali). Aliskiren exerted significant anti-albuminuric effects, whereas valsartan failed to ameliorate the albuminuria in the first four weeks. Surprisingly, the increasing dosage of valsartan in the Val-Val50 group showed non-significant tendencies to attenuate the albuminuria compared with vehicle infusion. Val-Val+Ali significantly suppressed the development of albuminuria and podocyte injury. Val-Val50 and Val-Val+Ali showed similar suppression of angiotensin II contents in the kidney of KKAy mice. In conclusion, the anti-albuminuric effect that was observed in the type 2 diabetic mice showing no anti-albuminuric effect by valsartan can be attributed to the add-on aliskiren.

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The neointima formation inside of polytetrafluoroethylene (PTFE) grafts may be associated with the migration of outside fibroblasts to the luminal surfaces. This study aimed to verify whether blockade of fibroblast migration can prevent neointima formation by testing two types of prosthetic vessels, the porous PTFE graft and the impermeable Grasil graft, respectively. After implantation of the PTFE graft in dogs, a time-dependent migration of outside fibroblasts to the luminal side occurred. Compared with the PTFE grafts, the total neointima formation in the Grasil grafts was significantly less. Although the neointima formation at the arterial or venous anastomotic regions did not significantly differ between the two grafts, the neointima at the middle region of the PTFE grafts was significantly evident than the Grasil grafts. The components of the renin–angiotensin system (RAS), such as angiotensin II and its receptor AT₁, as well as the forming enzymes of the RAS (angiotensin-converting enzyme and chymase), were all detectable in the grafts’ surrounding tissues. Neointima formation at the middle region of the prosthetic vessels could be suppressed almost completely by the blockade of outside fibroblast migration, indicating that outside fibroblasts play a key role in the formation of neointima in this region.

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The pharmacological activity of SU11274 is primarily due to its inhibition of hepotocyte growth factor receptor (c-Met) kinase overexpression. In this study, we demonstrated that the pathway involved in SU11274-induced autophagy was presumably through inhibition of c-Met and its down-stream pathways, including phosphatidylinositol 3-kinases – Akt (PI3K–Akt) and the growth factor receptor bound protein-2 / son of sevenless – Ras – p38 MAPK (Grb2/SOS–Ras–p38) pathway. SU11274 time-dependently induced the generation of superoxide anion (O₂^•−) and hydrogen peroxide (H₂O₂). There is a negative feedback loop between reactive oxygen species (ROS) induction and SU11274. Then, we investigated the role of ROS in protecting cells against SU11274-induced autophagic cell death in A549 cells. O₂^•− and H₂O₂ generation activated c-Met–PI3K–Akt and c-Met–Grb2/SOS–Ras–p38 signaling pathways, which were suppressed by O₂^•− scavenger superoxide dismutase (SOD) and H₂O₂ scavenger catalase. In conclusion, O₂^•− and H₂O₂ evoked cell resistance to SU11274 via activating c-Met–PI3K–Akt and c-Met–Grb2/SOS–Ras–p38 pathways in A549 cells. SU11274 also induced ROS generation in Caenorhabditis elegans.

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The senescence accelerated prone mouse strain 8 (SAMP8) develops age-related deficits in learning and memory. Effects of the azaindolizinone derivative ZSET1446/ST101, a newly synthesized cognitive enhancer, on cognitive impairment and deposition of amyloid β (Aβ) were assessed in the SAMP8. ZSET1446 was administered in drinking water at estimated doses of 0.002, 0.01, and 0.1 mg/kg per day from the age of 8 months. The SAMP8 at the age of 8 months showed cognitive impairment in a novel object recognition task compared with young SAMP8 at the age of 8 weeks. Further, grading scores were gradually increased from 9 to 12 months and Aβ-like immunoreactivity in the hippocampus was increased at the age of 10 months. ZSET1446 ameliorated cognitive deficits of SAMP8 after 4, 8, 12, and 16 weeks of treatment in a novel object recognition test. ZSET1446 also reduced grading scores of SAMP8 after 16 weeks of treatment. Further, 8-week treatment of ZSET1446 significantly reduced the total number of Aβ-positive granules in the hippocampus. These results suggest that ZSET1446 shows ameliorating effects on SAMP8 partly due to the suppression of an increase of Aβ-deposition in the hippocampus.

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The present study was carried out to investigate the protective effects of tempol on renal function and the underlying mechanism in streptozotocin-induced diabetic rats. The diabetic rats were randomly divided into the model group (without tempol) and tempol group (1 mM tempol in drinking water for 6 weeks). Nondiabetic rats were served as the Control group. The mRNA expression of canonical transient receptor potential 6 (TRPC6), transforming growth factor (TGF)-β₁, and type IV collagen (Col IV) were examined. The malondialdehyde (MDA) level, activities of superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) in renal tissues were measured to assess redox status in kidneys. We found that tempol significantly reduced 24-h urine output and urine albuminuria excretion in the diabetic rats. Compared with the model group, the concentration of MDA was significantly lower in the tempol group. In addition, diabetes decreased activities of SOD and GSH-Px and these responses were prevented by tempol treatment. Moreover, in diabetic rats, the mRNA expression levels of TGF-β₁ and Col IV were upregulated. TRPC6 mRNA expression level was down-regulated in diabetic kidneys. However, all of these diabetic effects were significantly suppressed by tempol treatment. These results suggest that chronic treatment of diabetic rats with tempol can protect kidneys, possibly by reducing expression of TGF-β₁, Col IV, and upregulating TRPC6 expression level.

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In the present study, we investigated the effect of melatonin on the GABA-induced current (I_GABA) and GABAergic miniature inhibitory postsynaptic currents (mIPSCs) in cultured rat hippocampal neurons using the whole-cell patch-clamp technique. We found that melatonin rapidly and reversibly enhanced I_GABA in a dose-dependent manner, with an EC₅₀ of 949 μM. Melatonin markedly enhanced the peak amplitude of a subsaturating I_GABA but not that of a saturating I_GABA. Interestingly, melatonin was effective only when GABA and melatonin were applied together. Furthermore, the effect of melatonin on I_GABA was voltage-independent and did not change the ion selectivity of the GABA_A receptor. The melatonin enhancement on I_GABA can not be blocked by luzindole, a melatonin receptor antagonist, indicating that melatonin-induced I_GABA enhancement was not via activation of its own membrane receptors. However, this enhancement may be mediated via high-affinity benzodiazepine sites as it was inhibited by the classical benzodiazepine antagonist flumazenil, suggesting an allosteric modulation of melatonin by binding to the sites of GABA_A receptors. In addition, melatonin increased both amplitude and frequency of GABAergic mIPSCs, indicating that melatonin enhances GABAergic inhibitory transmission. Hence, our observation that melatonin has an enhancing effect on the GABAergic system may implicate a potential pathway for the neuroprotective effects of melatonin.

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In this study, we explored whether phloroglucinol (1,3,5-trihydroxybenzene) exerts protective effects against oxidative stress–induced cytotoxicity in SH-SY5Y cells, a neuroblastoma cell line. The central nervous system is especially vulnerable to oxidative stress because the brain consumes large amounts of energy to perform its complicated functions, but contains a lower level of anti-oxidant enzymes compared with other peripheral tissues. In SH-SY5Y cultures, pretreatment with 10 μg/ml of phloroglucinol attenuates the cytotoxicity of hydrogen peroxide. In addition, when assessed with 2′,7′-dichlorofluorescein diacetate dye, the increase in reactive oxygen species (ROS) induced by hydrogen peroxide was significantly reduced by pretreatment with phloroglucinol. ROS is known to cause lipid peroxidation of the cell membranes, the carbonylation of intracellular proteins, and DNA damage, which can lead to various cellular dysfunctions and eventually cellular death. We found that pretreatment with phloroglucinol down-regulated the levels of 8-isoprostane, protein carbonylation, and 8-hydroxy deoxyguanine caused by hydrogen peroxide treatment in SH-SY5Y cells. These results indicate that phloroglucinol exerts protective effects against oxidative stress-induced cell damage in SH-SY5Y cells.

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