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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Research on the biochemistry and physiology of l-arginine has remained an attractive area for scientists over the last 100 years due to its diverse physiological functions in mammals. Research on l-arginine was boosted after the identification of nitric oxide (NO) and agmatine and their physiological importance. NO directly modulates ion channels, activates soluble guanylyl cyclase and other important proteins by ADP ribosylation and nitrosylation and binding to heme or iron-sulfur clusters. These modifications and interaction with heme might activate or inhibit various protein kinases, phosphatases and modulate transcription of various nuclear factors to possibly cause cardiovascular diseases like hypertension, ischemia, diabetes, atherosclerosis and angiogenesis. Agmatine holds the key to prevent the toxic effects associated with induction of NO synthesis by its ability to inhibit inducible nitric oxide synthase (iNOS). Agmatine is also synthesized from l-arginine by the enzyme arginine decarboxylase and displays a significant potential in cardiovascular system. Agmatine, with the myriad of effects on calcium homeostasis, seems to modulate various functions in the heart, brain and vasculature. The present review compiles the recent development to improve the understanding the role played by l-arginine-metabolic pathways in cardiovascular system. Though l-arginine and its metabolites are well known to affect various cardiovascular physiologies, the currently available literature is still not sufficient to validate the prophylactic/therapeutic efficacy of l-arginine. l-Arginine and its metabolites, NO and agmatine still hold the key for future research in cardiovascular system.
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PMID:Vascular regulation by the L-arginine metabolites, nitric oxide and agmatine. 1499 49

Brain edema is frequently shown after cerebral ischemia. It is an expansion of brain volume because of increasing water content in brain. It causes to increase mortality after stroke. Agmatine, formed by the decarboxylation of L-arginine by arginine decarboxylase, has been shown to be neuroprotective in trauma and ischemia models. The purpose of this study was to investigate the effect of agmatine for brain edema in ischemic brain damage and to evaluate the expression of aquaporins (AQPs). Results showed that agmatine significantly reduced brain swelling volume 22 h after 2 h middle cerebral artery occlusion in mice. Water content in brain tissue was clearly decreased 24 h after ischemic injury by agmatine treatment. Blood-brain barrier (BBB) disruption was diminished with agmatine than without. The expressions of AQPs-1 and -9 were well correlated with brain edema as water channels, were significantly decreased by agmatine treatment. It can thus be suggested that agmatine could attenuate brain edema by limiting BBB disruption and blocking the accumulation of brain water content through lessening the expression of AQP-1 after cerebral ischemia.
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PMID:Agmatine attenuates brain edema through reducing the expression of aquaporin-1 after cerebral ischemia. 2002 50

Earlier investigations from our laboratory demonstrated that the expression of matrix metalloproteinases (MMPs) was down-regulated by exogenously administered agmatine against ischemia-like injuries in the murine brain capillary endothelial (bEnd.3) cells. In our present study, we intended to investigate the mechanism involved in the inhibition of MMPs in bEnd.3 cells infected with retroviral containing human arginine decarboxylase (hADC) gene which can synthesize agmatine endogenously (ADCDeltabEnd.3 cells). The ADCDeltabEnd.3 cells were subjected to oxygen glucose deprivation (OGD, 6 hrs) with reperfusion (18 hrs). High performance liquid chromatography (HPLC) analysis revealed the high levels of agmatine in the ADCDeltabEnd.3 cells compared to other experimental groups. The results demonstrated significant decrease in cell death and increase in the nitric oxide (NO) production in the ADCDeltabEnd.3 cells. The increased expression of MMP-2 and MMP-9, and decreased expression of endothelial nitric oxide synthase (eNOS) by ischemic injury was attenuated in ADCDeltabEnd.3 cells. Moreover, the expression of activating transcription factor 3 (ATF3) was increased significantly in ADCDeltabEnd.3 cells. In addition, the suppression of the MMP-2 and MMP-9 expression in ADCDeltabEnd.3 cells was prevented with ATF3 small interfering RNA (siRNA) treatment. These results suggest that the endogenous agmatine in ADCDeltabEnd.3 cells inhibits the MMPs expression mediated via the regulation of eNOS, NO and ATF3.
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PMID:Endogenous agmatine inhibits cerebral vascular matrix metalloproteinases expression by regulating activating transcription factor 3 and endothelial nitric oxide synthesis. 2056 Aug 78

Nitric oxide (NO) production by endothelial nitric oxide synthase (eNOS) plays a protective role in cerebral ischemia by maintaining vascular permeability, whereas NO derived from neuronal and inducible NOS is neurotoxic and can participate in neuronal damage occurring in ischemia. Matrix metalloproteinases (MMPs) are up-regulated by ischemic injury and degrade the basement membrane if brain vessels to promote cell death and tissue injury. We previously reported that agmatine, synthesized from L-arginine by arginine decarboxylase (ADC) which is expressed in endothelial cells, has shown a direct increased eNOS expression and decreased MMPs expression in bEnd3 cells. But, there are few reports about the regulation of eNOS by agmatine in ischemic animal model. In the present study, we examined the expression of eNOS and MMPs by agmatine treatment after transient global ischemia in vivo. Global ischemia was induced with four vessel occlusion (4-VO) and agmatine (100 mg/kg) was administered intraperitoneally at the onset of reperfusion. The animals were euthanized at 6 and 24 hours after global ischemia and prepared for other analysis. Global ischemia led severe neuronal damage in the rat hippocampus and cerebral cortex, but agmatine treatment protected neurons from ischemic injury. Moreover, the level and expression of eNOS was increased by agmatine treatment, whereas inducible NOS (iNOS) and MMP-9 protein expressions were decreased in the brain. These results suggest that agmatine protects microvessels in the brain by activation eNOS as well as reduces extracellular matrix degradation during the early phase of ischemic insult.
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PMID:Regulation of endothelial nitric oxide synthase by agmatine after transient global cerebral ischemia in rat brain. 2121 63

Agmatine, a cationic polyamine synthesized after decarboxylation of L-arginine by the enzyme arginine decarboxylase, is an endogenous neuromodulator that emerges as a potential agent to manage diverse central nervous system (CNS) disorders. Consistent with its neuromodulatory and neuroprotective properties, there is increasing number of preclinical studies demonstrating the beneficial effects of exogenous agmatine administration on depression, anxiety, hypoxic ischemia, nociception, morphine tolerance, memory, Parkinson`s disease, Alzheimer`s disease, traumatic brain injury related alterations/disorders and epilepsy. The aim of this review is to summarize the knowledge about the effects of agmatine in CNS and point out its potential as new pharmacological treatment for diverse neurological and neurodegenerative diseases. Moreover, some molecular mechanisms underlying the neuroprotective effects of agmatine will be discussed.
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PMID:Role of agmatine in neurodegenerative diseases and epilepsy. 2489 10

Ischemic preconditioning (IP) is one of the most important endogenous mechanisms that protect the cells against ischemia-reperfusion (I/R) injury. However, the exact molecular mechanisms remain unclear. In this study, we showed that changes in the level of agmatine were correlated with ischemic tolerance. Changes in brain edema, infarct volume, level of agmatine, and expression of arginine decarboxylase (ADC) and nitric oxide synthases (NOS; inducible NOS [iNOS] and neural NOS [nNOS]) were analyzed during I/R injury with or without IP in the rat brain. After cerebral ischemia, brain edema and infarct volume were significantly reduced in the IP group. The level of agmatine was increased before and during ischemic injury and remained elevated in the early reperfusion phase in the IP group compared to the experimental control (EC) group. During IP, the level of plasma agmatine was increased in the early phase of IP, but that of liver agmatine was abruptly decreased. However, the level of agmatine was definitely increased in the ipsilateral and contralateral hemisphere of brain during the IP. IP also increased the expression of ADC-the enzyme responsible for the synthesis of endogenous agmatine-before, during, and after ischemic injury. In addition, ischemic injury increased endogenous ADC expression in the EC group. The expression of nNOS was reduced in the I/R injured brain in the IP group. These results suggest that endogenous increased agmatine may be a component of the ischemic tolerance response that is induced by IP. Agmatine may have a pivotal role in endogenous ischemic tolerance.
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PMID:Endogenous Agmatine Induced by Ischemic Preconditioning Regulates Ischemic Tolerance Following Cerebral Ischemia. 2930 5