Exogenous agmatine has neuroprotective effects against restraint-induced structural changes in the rat brain

Preventive putative effect of agmatine on cognitive and molecular outcomes in ventral tegmental area of male offspring following physical and psychological prenatal stress

Prenatal stress (PS) results from a maternal experience of stressful events during pregnancy, which has been associated with an increased risk of behavioral disorders including substance abuse and anxiety in the offspring. PS is known to result in heightened dopamine release in the ventral tegmental area (VTA), in part through the effects of corticotropin-releasing hormone, which directly excites dopaminergic cells. It has recently been suggested that agmatine plays a role in modulating anxiety-like behaviors. In this study, we investigated whether agmatine could reduce negative cognitive outcomes in male mice prenatally exposed to psychological/physical stress, and whether this could be associated with molecular changes in VTA. Agmatine (37.5 mg/kg) was administrated 30 min prior to PS induction in pregnant Swiss mice. Male offspring were evaluated in a series of behavioral and molecular assays. Findings demonstrated that agmatine reduced the impairment in locomotor activity induced by both psychological and physical PS. Agmatine also decreased heightened conditioned place preference to morphine seen in PS offspring. Moreover, agmatine ameliorated the anxiety-like behavior and drug-seeking behavior induced by PS in the male offspring. Molecular effects were seen in VTA as the enhanced brain-derived neurotrophic factor (BDNF) induced by PS in the VTA was reduced by agmatine. Behavioral tests indicate that agmatine exerts a protective effect on PS-induced impairments in male offspring, which could be due in part to agmatine-associated molecular alterations in the VTA. Taken together, our data suggest that prenatal treatment with agmatine exerts protective effect against negative consequences of PS on the development of affective circuits in the offspring.

Effect of Agmatine on a mouse model of allergic airway inflammation: A comparative study

INTRODUCTION

Asthma is a chronic lung disease that injures and constricts the airways. This study evaluates the effects of agmatine on ovalbumin (OVA)-induced allergic inflammation of the airways.

METHODS

OVA sensitization by intraperitoneal injection was used to induce airway inflammation in mice on days 0 and 7; then the mice were challenged using beclomethasone (150 µg/kg, inhalation), a standard anti-asthmatic drug, from day 14 to day 16. Furthermore, agmatine (200 mg/kg) was intraperitoneally injected on day 0 and then daily for 16 days, followed by OVA challenge. The lung weight ratio, total and differential cell counts, TNF-α, interleukin-5 (IL-5) and IL-13 in bronchoalveolar lavage fluid (BALF), lung nitrite/nitrate (NO), and oxidative parameters were determined. Moreover, histopathological and immunohistochemical staining was employed.

RESULTS

Injection of agmatine (200 mg/kg) for 16 days significantly attenuated inflammation of the airways. The levels of BALF inflammatory cells, TNF-α, IL-5, IL-13, lung NO, and malondialdehyde (MDA), significantly decreased with concomitant elevation of superoxide dismutase (SOD) levels. Histological and immunohistochemical analyses of mast cells paralleled to biochemical improvements.

CONCLUSION

Finally, this study illustrated that agmatine attenuates the allergic inflammation of airways caused by OVA by mitigating cytokines release, NO expression, and oxidative stress.

Maintenance of the Neuroprotective Function of the Amino Group Blocked Fluorescence-Agmatine

Agmatine, an endogenous derivative of arginine, has been found to be effective in treating idiopathic pain, convulsion, stress-mediated behavior, and attenuate the withdrawal symptoms of drugs like morphine. In the early stages of ischemic brain injury in animals, exogenous agmatine treatment was found to be neuroprotective. Agmatine is also considered as a putative neurotransmitter and is still an experimental drug. Chemically, agmatine is called agmatine 1-(4-aminobutyl guanidine). Crystallographic study data show that positively-charged guanidine can bind to the protein containing Gly and Asp residues, and the amino group can interact with the complimentary sites of Glu and Ser. In this study, we blocked the amino end of the agmatine by conjugating it with FITC, but the guanidine end was unchanged. We compared the neuroprotective function of the agmatine and agmatine-FITC by treating them in neurons after excitotoxic stimulation. We found that even the amino end blocked neuronal viability in the excitotoxic condition, by NMDA treatment for 1 h, was increased by agmatine-FITC, which was similar to that of agmatine. We also found that the agmatine-FITC treatment reduced the expression of nitric oxide production in NMDA-treated cells. This study suggests that even if the amino end of agmatine is blocked, it can perform its neuroprotective function.

Up-regulation of HIF-1α is associated with neuroprotective effects of agmatine against rotenone-induced toxicity in differentiated SH-SY5Y cells

Agmatine, a metabolite generated by arginine decarboxylation, has been reported as neuromodulator and neuroactive substance. Several findings suggest that agmatine displays neuroprotective effects in several models of neurodegenerative disorders, such as Parkinson's disease (PD). It has been hypothesized that biogenic amines may be involved in neuroprotection by scavenging oxygen radicals, thus preventing the generation of oxidative stress. Mitochondrial dysfunction, that leads to a reduction of oxygen consumption, followed by activation of prolyl hydroxylase and decrease of hypoxia-inducible factor 1 alpha (HIF-1α) levels, has been demonstrated to play a role in PD pathogenesis. Using rotenone-treated differentiated SH-SY5Y cells as the in vitro PD model, we here investigated the molecular mechanisms underlying agmatine neuroprotective effects. Our results showed that the preliminary addition of agmatine induces HIF-1α activation, and prevents the rotenone-induced production of free radical species, and the activation of apoptotic pathways by inhibiting mitochondrial membrane potential decrease and caspase 3 as well as cytochrome c increase. Notably, these effects are mediated by HIF-1α, as indicated by experiments using a HIF-1α inhibitor. The present findings suggest that the treatment with agmatine is able to counteract the neuronal cell injury evoked by mitochondrial toxins.

Evaluation of plasma agmatine level and its metabolic pathway in patients with bipolar disorder during manic episode and remission period

Objectives: Agmatine is a cationic amine resulting from the decarboxylation of l-arginine. Agmatine has neuroprotective, anti-inflammatory, anti-stress, and anti-depressant properties. In this study, plasma agmatine, arginine decarboxylase, and agmatinase levels were measured during manic episode and remission period in patients with bipolar disorder. Methods: Thirty healthy volunteers and 30 patients who meet Bipolar Disorder Manic Episode diagnostic criteria were included in the study. Additionally, the changes in the patient group between manic episode and remission period were examined. We evaluated the relationship between levels of l-arginine and arginine decarboxylase in the agmatine synthesis pathway, and level of agmatinase that degrades agmatine. Results: Levels of agmatine and l-arginine were significantly increased than control group during manic episode (p < .01). All parameters were increased during manic episode compared to remission period (p < .05). Agmatinase was significantly decreased both during manic episode (p < .01) and remission period (p < .05) in comparison to the control group. Arginine decarboxylase levels did not show a significant difference between the groups (p > .05). Conclusions: This study indicate that there may be a relationship between bipolar disorder and agmatine and its metabolic pathway. Nonetheless, we believe more comprehensive studies are needed in order to reveal the role of agmatine in etiology of bipolar disorder. Key points Agmantine, agmatinase, l-arginine and arginine decarboxylase levels in BD have not been explored before. Various neuro-chemical mechanisms act to increase agmatine in BD; however, agmatine could have elevated to compensate agmatine deficit prior to the manifestation of the disease as in schizophrenia. Elevated agmatine degradation resulting from excess expression of agmatinase which is suggested to be effective in pathogenesis of mood disorders was compensated by this way. Elevated agmatine may be one of the causes which play a role in mania development. Elevated agmatine levels are also suggested to trigger psychosis and be related with the etiology of manic episode and lead to BD.

A novel comprehensive paradigm for the etiopathogenesis of multiple sclerosis: therapeutic approaches and future perspectives on its treatment

It is well recognized that variation in the geographical distribution of prevalence of multiple sclerosis (MS) exists: increasing the latitude its prevalence increases as well, but the underlying causes of such dissimilarity still remained elusive as of today. Currently, the most accredited hypothesis is that the closer to the equator the more pronounced is the amount of sunlight which, in turn, increases the production of vitamin D. Cholecalciferol is indeed deficient in MS patients, but this factor does not explain by itself the etiopathogenesis of the disease. In the present study, to search for a pattern and provide a model of the disease's etiology consistent with this regional factor, as well with its changing ethnic, sex-ratio, lifestyle variations and the other unexplained aspects of MS, an extensive analysis of peer-reviewed literature and data was conducted. The arisen hypothesis was that, increasing the latitude, the factor that varies and can have the stronger effect on the human organism, is the continuous and ever-increasing diversity of the natural light-dark cycle. The consequent effort of the suprachiasmatic nucleus to entrain the organism's circadian rhythm affects the hypothalamic-pituitary-adrenal axis resulting in desynchronizing the central and peripheral circadian clocks and pathologizing the immunitary system. To verify such hypothesis, a theoretical framework of the etiopathogenesis, coherent with the gathered literature, was conceived and a demonstration to corroborate it was eventually devised and performed. The results underscored that people living in countries subjected to a further circadian disruptive factor, as daylight saving time, have a 6.35 times higher prevalence of MS than States placed on their same latitude that do not observe it, thus strongly supporting the hypothesis. As further reinforcement of the conclusions, it is worth mentioning that the levels of polyamines rise abruptly in autoimmune diseases. Moreover, among their numerous roles, these polycations participate to the regulation of the circadian clock so their sudden variation might disrupt it. Following these interesting findings, new perspectives in therapies are, therefore, proposed.

Neuroprotective effect of agmatine (decarboxylated l-arginine) against oxidative stress and neuroinflammation in rotenone model of Parkinson's disease

Parkinson's disease (PD) is the second most common age-related neurodegenerative disease after Alzheimer's disease, characterized by loss of dopaminergic neurons in substantia nigra pars compacta, accompanied by motor and nonmotor symptoms. The neuropathological hallmarks of PD are well reported, but the etiology of the disease is still undefined; several studies assume that oxidative stress, mitochondrial defects, and neuroinflammation play vital roles in the progress of the disease. The current study was established to investigate the neuroprotective effect of agmatine on a rotenone (ROT)-induced experimental model of PD. Adult male Sprague Dawley rats were subcutaneously injected with ROT at a dose of 2 mg/kg body weight for 35 days. Agmatine was injected intraperitoneally at 50 and 100 mg/kg body weight, 1 h prior to ROT administration. ROT-treated rats that received agmatine showed better performance on beam walking and an elevated number of rears within the cylinder test. In addition, agmatine reduced midbrain malondialdehyde as an indication of lipid peroxidation, pro-inflammatory cytokines including tumor necrosis factor alpha and interleukin-1β, and glial fibrillary acidic protein. Moreover, agmatine was responsible for preventing loss of tyrosine hydroxylase-positive neurons. In conclusion, our study showed that agmatine possesses a dose-dependent neuroprotective effect through its antioxidant and anti-inflammatory activities. These findings need further clinical investigations of agmatine as a promising neuroprotective agent for the future treatment of PD.

Agmatine attenuates chronic unpredictable mild stress-induced anxiety, depression-like behaviours and cognitive impairment by modulating nitrergic signalling pathway

Agmatine, a neurotransmitter/neuromodulator, has shown to exert numerous effects on the CNS. Chronic stress is a risk factor for development of depression, anxiety and deterioration of cognitive performance. Compelling evidences indicate an involvement of nitric oxide (NO) pathway in these disorders. Hence, investigation of the beneficial effects of agmatine on chronic unpredictable mild stress (CUMS)-induced depression, anxiety and cognitive performance with the involvement of nitrergic pathway was undertaken. Mice were subjected to a battery of stressors for 28days. Agmatine (20 and 40mg/kg, i.p.) alone and in combination with NO modulators like L-NAME (15mg/kg, i.p.) and l-arginine (400mg/kg i.p.) were administered daily. The results showed that 4-weeks CUMS produces significant depression and anxiety-like behaviour. Stressed mice have also shown a significant high serum corticosterone (CORT) and low BDNF level. Chronic treatment with agmatine produced significant antidepressant-like behaviour in forced swim test (FST) and sucrose preference test, whereas, anxiolytic-like behaviour in elevated plus maze (EPM) and open field test (OFT) with improved cognitive impairment in Morris water maze (MWM). Furthermore, agmatine administration reduced the levels of acetylcholinesterase and oxidative stress markers. In addition, agmatine treatment significantly increased the BDNF level and inhibited serum CORT level in stressed mice. Treatment with L-NAME (15mg/kg) potentiated the effect of agmatine whereas l-arginine abolished the anxiolytic, antidepressant and neuroprotective effects of agmatine. Agmatine showed marked effect on depression and anxiety-like behaviour in mice through nitrergic pathway, which may be related to modulation of oxidative-nitrergic stress, CORT and BDNF levels.

Agmatine, a potential novel therapeutic strategy for depression

Major depressive disorder is the most common psychiatric disorder with lifetime prevalence of up to 20% worldwide. It is responsible for more years lost to disability than any other disorder. Despite the fact that current available antidepressant drugs are safe and effective, they are far from ideal. In addition to the need to administer the drugs for weeks or months to obtain clinical benefit, side effects are still a serious problem. Agmatine is an endogenous polyamine synthesized by the enzyme arginine decarboxylase. It modulates several receptors and is considered as a neuromodulator in the brain. In this review, studies demonstrating the antidepressant effects of agmatine are presented and discussed, as well as, the mechanisms of action related to these effects. Also, the potential beneficial effects of agmatine for the treatment of other neurological disorders are presented. In particular, we provide evidence to encourage future clinical studies investigating agmatine as a novel antidepressant drug.

Involvement of the agmatinergic system in the depressive-like phenotype of the Crtc1 knockout mouse model of depression

Recent studies implicate the arginine-decarboxylation product agmatine in mood regulation. Agmatine has antidepressant properties in rodent models of depression, and agmatinase (Agmat), the agmatine-degrading enzyme, is upregulated in the brains of mood disorder patients. We have previously shown that mice lacking CREB-regulated transcription coactivator 1 (CRTC1) associate behavioral and molecular depressive-like endophenotypes, as well as blunted responses to classical antidepressants. Here, the molecular basis of the behavioral phenotype of Crtc1(-/-) mice was further examined using microarray gene expression profiling that revealed an upregulation of Agmat in the cortex of Crtc1(-/-) mice. Quantitative polymerase chain reaction and western blot analyses confirmed Agmat upregulation in the Crtc1(-/-) prefrontal cortex (PFC) and hippocampus, which were further demonstrated by confocal immunofluorescence microscopy to comprise an increased number of Agmat-expressing cells, notably parvalbumin- and somatostatin-positive interneurons. Acute agmatine and ketamine treatments comparably improved the depressive-like behavior of male and female Crtc1(-/-) mice in the forced swim test, suggesting that exogenous agmatine has a rapid antidepressant effect through the compensation of agmatine deficit because of upregulated Agmat. Agmatine rapidly increased brain-derived neurotrophic factor (BDNF) levels only in the PFC of wild-type (WT) females, and decreased eukaryotic elongation factor 2 (eEF2) phosphorylation in the PFC of male and female WT mice, indicating that agmatine might be a fast-acting antidepressant with N-methyl-D-aspartate (NMDA) receptor antagonist properties. Collectively, these findings implicate Agmat in the depressive-like phenotype of Crtc1(-/-) mice, refine current understanding of the agmatinergic system in the brain and highlight its putative role in major depression.

Chronic agmatine treatment prevents behavioral manifestations of nicotine withdrawal in mice

Smoking cessation exhibits an aversive withdrawal syndrome characterized by both increases in somatic signs and affective behaviors including anxiety and depression. In present study, abrupt withdrawal of daily nicotine injections (2mg/kg, s.c., four times daily, for 10 days) significantly increased somatic signs viz. rearing, grooming, jumping, genital licking, leg licking, head shakes with associated depression (increased immobility in forced swim test) as well as anxiety (decreased the number of entries and time spent in open arm in elevated plus maze) in nicotine dependent animals. The peak effect was observed at 24h time point of nicotine withdrawal. Repeated administration of agmatine (40-80µg/mouse, i.c.v.) before the first daily dose of nicotine from day 5 to 10 attenuated the elevated scores of somatic signs and abolished the depression and anxiety like behavior induced by nicotine withdrawal in dependent animals. However, in separate groups, its acute administration 30min before behavior analysis of nicotine withdrawal was ineffective. This result clearly shows the role of agmatine in development of nicotine dependence and its withdrawal. In extension to behavioral experiments, brain agmatine analyses, carried out at 24h time point of nicotine withdrawal demonstrated marked decrease in basal brain agmatine concentration as compared to control animals. Taken together, these data support the role of agmatine as common biological substrate for somatic signs and affective symptoms of nicotine withdrawal. This data may project therapies based on agmatine in anxiety, depression and mood changes associated with tobacco withdrawal.

Neuropeptide Y in the central nucleus of amygdala regulates the anxiolytic effect of agmatine in rats

In the present study, modulation of anxiolytic action of agmatine by neuropeptide Y (NPY) in the central nucleus of amygdala (CeA) is evaluated employing Vogel's conflict test (VCT) in rats. The intra-CeA administration of agmatine (0.6 and 1.2µmol/rat), NPY (10 and 20pmol/rat) or NPY Y1/Y5 receptors agonist [Leu(31), Pro(34)]-NPY (30 and 60pmol/rat) significantly increased the number of punished drinking licks following 15min of treatment. Combination treatment of subeffective dose of NPY (5pmol/rat) or [Leu(31), Pro(34)]-NPY (15pmol/rat) and agmatine (0.3µmol/rat) produced synergistic anxiolytic-like effect. However, intra-CeA administration of selective NPY Y1 receptor antagonist, BIBP3226 (0.25 and 0.5mmol/rat) produced anxiogenic effect. In separate set of experiment, pretreatment with BIBP3226 (0.12mmol/rat) reversed the anxiolytic effect of agmatine (0.6µmol/rat). Furthermore, we evaluated the effect of intraperitoneal injection of agmatine (40mg/kg) on NPY-immunoreactivity in the nucleus accumbens shell (AcbSh), lateral part of bed nucleus of stria terminalis (BNSTl) and CeA. While agmatine treatment significantly decreased the fibers density in BNSTl, increase was noticed in AcbSh. In addition, agmatine reduced NPY-immunoreactive cells in the AcbSh and CeA. Immunohistochemical data suggest the enhanced transmission of NPY from the AcbSh and CeA. Taken together, this study suggests that agmatine produced anxiolytic effect which might be regulated via modulation of NPYergic system particularly in the CeA.

Imidazoline binding sites mediates anticompulsive-like effect of agmatine in marble-burying behavior in mice

Agmatine is a cationic amine formed by decarboxylation of l-arginine by the mitochondrial enzyme arginine decarboxylase and widely distributed in mammalian brain. Although the precise function of endogenous agmatine has been largely remained unclear, its exogenous administration demonstrated beneficial effects in several neurological and psychiatric disorders. This study was planned to examine the role of imidazoline binding sites in the anticompulsive-like effect of agmatine on marble-burying behavior. Agmatine (20 and 40mg/kg, ip), mixed imidazoline I1/α2 agonists clonidine (60µg/kg, ip) and moxonidine (0.25mg/kg, ip), and imidazoline I2 agonist 2- BFI (10mg/kg, ip) showed significant inhibition of marble burying behavior in mice. In combination studies, the anticompulsive-like effect of agmatine (10mg/kg, ip) was significantly potentiated by prior administration of moxonidine (0.25mg/kg, ip) or clonidine (30µg/kg,) or 2-BFI (5mg/kg, ip). Conversely, efaroxan (1mg/kg, ip), an I1 antagonist and idazoxan (0.25mg/kg, ip), an I2 antagonist completely blocked the anticompulsive-like effect of agmatine (10mg/kg, ip). These drugs at doses used here did not influence the basal locomotor activity in experimental animals. These results clearly indicated the involvement of imidazoline binding sites in anti-compulsive-like effect of agmatine. Thus, imidazoline binding sites can be explored further as novel therapeutic target for treatment of anxiety and obsessive compulsive disorders.

Agmatine attenuates chronic unpredictable mild stress induced behavioral alteration in mice

Chronic stress exposure and resulting dysregulation of the hypothalamic pituitary adrenal axis develops susceptibility to variety of neurological and psychiatric disorders. Agmatine, a putative neurotransmitter has been reported to be released in response to various stressful stimuli to maintain the homeostasis. Present study investigated the role of agmatine on chronic unpredictable mild stress (CUMS) induced behavioral and biochemical alteration in mice. Exposure of mice to CUMS protocol for 28 days resulted in diminished performance in sucrose preference test, splash test, forced swim test and marked elevation in plasma corticosterone levels. Chronic agmatine (5 and 10 mg/kg, ip, once daily) treatment started on day-15 and continued till the end of the CUMS protocol significantly increased sucrose preference, improved self-care and motivational behavior in the splash test and decreased duration of immobility in the forced swim test. Agmatine treatment also normalized the elevated corticosterone levels and prevented the body weight changes in chronically stressed animals. The pharmacological effect of agmatine was comparable to selective serotonin reuptake inhibitor, fluoxetine (10mg/kg, ip). Results of present study clearly demonstrated the anti-depressant like effect of agmatine in chronic unpredictable mild stress induced depression in mice. Thus the development of drugs based on brain agmatinergic modulation may represent a new potential approach for the treatment of stress related mood disorders like depression.

Agmatine protects against scopolamine-induced water maze performance impairment and hippocampal ERK and Akt inactivation

Cholinergic brain activity plays a significant role in memory. Scopolamine a muscarinic cholinergic antagonist is known to induce impairment in Morris water maze performance, the task which is mainly dependent on the hippocampus. It is suggested that hippocampal ERK and Akt activation play roles in synaptic plasticity and some types of learning and memory. Agmatine, a polyamine derived from l-arginine decarboxylation, is recently shown to exert some neuroprotective effects. This study was aimed to investigate if agmatine could reverse scopolamine-induced memory impairment and possible hippocampal ERK and Akt activity alteration. Adult male Sprague-Dawley rats weighing 200-250 g were randomly assigned into 5 groups. The animals were trained for 3 days in Morris water maze and in day 4 their memory retention was assessed in probe trial which was consisted of a 60 s trial with no platform. Scopolamine (1 mg/kg/ip) or saline were injected 30 min and agmatine (20 or 40 mg/kg/ip) was administered 60 min before each session. The hippocampi were isolated after behavioral studies and western blotting studies on hippocampal lysates were done to determine the levels of activated ERK and Akt. Scopolamine treatment not only impaired water maze learning and memory, but also decreased the amount of phosphorylated (activated) ERK and Akt. Agmatine pre-treatment prevented both the learning impairment and hippocampal ERK and Akt inactivation induced by scopolamine. It seems that agmatine may act as a candidate substance against amnesia.

Agmatine effects on mitochondrial membrane potential and NF-κB activation protect against rotenone-induced cell damage in human neuronal-like SH-SY5Y cells

Agmatine, an endogenous arginine metabolite, has been proposed as a novel neuromodulator that plays protective roles in the CNS in several models of cellular damage. However, the mechanisms involved in these protective effects in neurodegenerative diseases are poorly understood. The present study was undertaken to investigate the effects of agmatine on cell injury induced by rotenone, commonly used in establishing in vivo and in vitro models of Parkinson's disease, in human-derived dopaminergic neuroblastoma cell line (SH-SY5Y). We report that agmatine dose-dependently suppressed rotenone-induced cellular injury through a reduction of oxidative stress. Similar effects were obtained by spermine, suggesting a scavenging effect for these compounds. However, unlike spermine, agmatine also prevented rotenone-induced nuclear factor-κB nuclear translocation and mitochondrial membrane potential dissipation. Furthermore, rotenone-induced increase in apoptotic markers, such as caspase 3 activity, Bax expression and cytochrome c release, was significantly attenuated with agmatine treatment. These findings demonstrate mitochondrial preservation with agmatine in a rotenone model of apoptotic cell death, and that the neuroprotective action of agmatine appears because of suppressing apoptotic signalling mechanisms. Thus, agmatine may have therapeutic potential in the treatment of Parkinson's disease by protecting dopaminergic neurons.

Beneficial effect of agmatine on brain apoptosis, astrogliosis, and edema after rat transient cerebral ischemia

Background

Although agmatine therapy in a mouse model of transient focal cerebral ischemia is highly protective against neurological injury, the mechanisms underlying the protective effects of agmatine are not fully elucidated. This study aimed to investigate the effects of agmatine on brain apoptosis, astrogliosis and edema in the rats with transient cerebral ischemia.

Methods

Following surgical induction of middle cerebral artery occlusion (MCAO) for 90 min, agmatine (100 mg/kg, i.p.) was injected 5 min after beginning of reperfusion and again once daily for the next 3 post-operative days. Four days after reperfusion, both motor and proprioception functions were assessed and then all rats were sacrificed for determination of brain infarct volume (2, 3, 5-triphenyltetrazolium chloride staining), apoptosis (TUNEL staining), edema (both cerebral water content and amounts of aquaporin-4 positive cells), gliosis (glial fibrillary acidic protein [GFAP]-positive cells), and neurotoxicity (inducible nitric oxide synthase [iNOS] expression).

Results

The results showed that agmatine treatment was found to accelerate recovery of motor (from 55 degrees to 62 degrees) and proprioception (from 54% maximal possible effect to 10% maximal possible effect) deficits and to prevent brain infarction (from 370 mm³ to 50 mm³), gliosis (from 80 GFAP-positive cells to 30 GFAP-positive cells), edema (cerebral water contents decreased from 82.5% to 79.4%; AQP4 positive cells decreased from 140 to 84 per section), apoptosis (neuronal apoptotic cells decreased from 100 to 20 per section), and neurotoxicity (iNOS expression cells decreased from 64 to 7 per section) during MCAO ischemic injury in rats.

Conclusions

The data suggest that agmatine may improve outcomes of transient cerebral ischemia in rats by reducing brain apoptosis, astrogliosis and edema.

Recombinant hexahistidine arginine decarboxylase (hisADC) induced endogenous agmatine synthesis during stress

The arginine decarboxylase (ADC) is a significant functional enzyme, synthesizes agmatine through arginine metabolism, and agmatine was reported to posses protective properties in various tissues. This study first optimized the conditions for efficient hexahistidine tagged human ADC (hisADC) gene delivery into mouse fibroblast cell line (NIH3T3) using retroviral vector (pLXSN). Later, the functionality of the delivered hisADC gene in synthesizing agmatine during H(2)O(2) injury in NIH3T3 was also elucidated. Amplification of hisADC gene was performed using hisADC specific primers under specified conditions. The hisADC PCR product (1.4 kb) was ligated with pLXSN considering the restriction enzyme sites. The complete hisADC pLXSN clone was transfected into PT67 cell line following CalPhos Mammalian transfection method. RT-PCR and western blot results showed the specific and strong detection of hisADC genes in hisADC PT67 transfected cells compared with normal control and pLXSN transfected PT67 cells. The retrovirus containing hisADC gene (vhisADC) was infected into NIH3T3 (vhisADC NIH) using polybrene reagent. Immunocytochemical results showed hisADC expression in the cytoplasm of vhisADC NIH. HPLC analysis revealed high agmatine concentration in the vhisADC NIH, and the induced agmatine synthesized from the retroviral gene delivery prevented vhisADC NIH from H(2)O(2) injury which is evident by the decrease in lactate dehydrogenase (P < 0.05) leakage into the medium and less number of propidium iodide positive cells during injury compared to control group. The obtained results provide compelling evidence that higher level of hisADC transgene expression completely triggered the endogenous agmatine synthesis during H(2)O(2) injury thus protecting NIH3T3 cells against cytotoxicity.

Agmatine prevents LPS-induced spatial memory impairment and hippocampal apoptosis

Neuroinflammation is associated with a number of neurodegenerative diseases. It is known that lipopolysaccharide (LPS) treatment induces neuroinflammation and memory deterioration. Agmatine, the metabolite of arginine by arginine decarboxylase, is suggested to be a neuroprotective agent. The aim of this study was to explore if agmatine can prevent LPS-induced spatial memory impairment and hippocampal apoptosis. Adult male Wistar rats (200-250 g) were trained in water maze for 4 days (3 days in hidden platform and the last day in visible platform task). Saline, LPS (250 microg/kg/ip) or (and) agmatine (5 or 10 mg/kg) were administered 4h before every training session. LPS treatment impaired water maze place learning while agmatine co-administration prevented it. Also western blot studies revealed that LPS induces hippocampal caspase-3 activation while agmatine treatment prevented it.

Neuroprotective effects of agmatine on oxygen-glucose deprived primary-cultured astrocytes and nuclear translocation of nuclear factor-kappa B

To better understand the neuroprotective actions of agmatine in ischemic insults, its effects on astrocytes were investigated using an in vitro oxygen-glucose deprivation (OGD) model. After primary culture, cortical astrocytes were moved into a closed anaerobic chamber and incubated in glucose-free culture media. 4 h later, the cells were restored to normoxic conditions and supplied with glucose for 20 h. The ability of agmatine to rescue astrocytes from OGD only and OGD followed by restoration (OGD-R) was assessed. Cell viability was monitored with or without 100 muM agmatine, using the lactate dehydrogenase (LDH) assay and annexin V flow cytometric assay. For morphological analysis, Hoechst 33258 and propidium iodide double nuclear staining was performed. Expression and phosphorylation of nuclear factor-kappa B (NF-kappaB) family proteins were also investigated by immunoblotting. Results showed that astrocytes had decreased viability following OGD and OGD-R and that agmatine treatment increased cell viability and induced NF-kappaB translocation into the nucleus. Finally, our studies revealed that agmatine can rescue astrocytes from death caused by ischemic and/or ischemic-perfusion neuronal injuries in vitro. Our findings provide new insights that may lead to a novel therapeutic strategy to reduce these kinds of neuronal injuries.

Repeated immobilization stress alters rat hippocampal and prefrontal cortical morphology in parallel with endogenous agmatine and arginine decarboxylase levels

Agmatine, an endogenous amine derived from decarboxylation of L-arginine catalyzed by arginine decarboxylase, has been proposed as a neurotransmitter or neuromodulator in the brain. In the present study, we examined whether agmatine has neuroprotective effects against repeated immobilization-induced morphological changes in brain tissues and possible effects of immobilization stress on endogenous agmatine levels and arginine decarboxylase expression in rat brains. Sprague-Dawley rats were subjected to 2h immobilization stress daily for 7 days. This paradigm significantly increased plasma corticosterone levels, and the glutamate efflux in the hippocampus as measured by in vivo microdialysis. Immunohistochemical staining with beta-tubulin III showed that repeated immobilization caused marked morphological alterations in the hippocampus and medial prefrontal cortex that were prevented by simultaneous treatment with agmatine (50mg/kg/day), i.p.). Likewise, endogenous agmatine levels measured by high-performance liquid chromatography in the prefrontal cortex, hippocampus, striatum and hypothalamus were significantly increased by immobilization, as compared to controls. The increased endogenous agmatine levels, ranging from 92 to 265% of controls, were accompanied by a significant increase of arginine decarboxylase protein levels in the same regions. These results demonstrate that the administration of exogenous agmatine protects the hippocampus and medial prefrontal cortex against neuronal insults caused by repeated immobilization. The parallel increase in endogenous brain agmatine and arginine decarboxylase protein levels triggered by repeated immobilization indicates that the endogenous agmatine system may play an important role in adaptation to stress as a potential neuronal self-protection mechanism.