Agmatine ameliorates diabetes type 2-induced nephropathy in rats

Objective:To assess the nephroprotective potential of agmatine in a rat model of streptozotocin-induced diabetic nephropathy.Methods:A single dose of streptozotocin(40 mg/kg)coupled with a fructose diet induced diabetes in Wistar rats.Agmatine(40 and 80 mg/kg)was administered to rats for 12 weeks.The body weight and fasting blood glucose were measured weekly.Insulin level,urine output,total protein,albumin,blood urea nitrogen,creatinine,and cystatin-C were also determined at the end of the experiment.Furthermore,superoxide dismutase,glutathione,interleukin-1β,interleukin-6,and tumor necrosis factor-alpha were evaluated in kidney tissue.Histopathological study was also performed using hematoxylin and eosin staining.Results:Agmatine at both doses significantly increased final body weight,and lowered fasting blood glucose,urine output,insulin,total protein,albumin,blood urea nitrogen,creatinine,and cystatin-C levels compared with the diabetic group(P<0.05).Inflammatory markers and antioxidant effect were significantly improved in agmatine-treated rats.Moreover,the histopathological changes in renal structure were ameliorated by agmatine treatment.Conclusions:Agmatine alleviates diabetic nephropathy by improving renal functions and reducing inflammation and oxidative stress.The molecular mechanisms of its nephroprotective actions need to be investigated in future study.

Neuroprotective effects of receptor imidazoline 2 and its endogenous ligand agmatine

Receptor imidazoline 2 （I2） is one of the imidazoline receptors with high affinity for [^3H]-idazoxan. Receptor I2, being classified into I2A and I28 subtypes, is mainly localized to the outer membrane of mitochondria in liver, kidney and brain. Receptor I2, displaying high similarity of sequence with monoamine oxidase-B （MAO-B）, is structurally related to MAO-B, but the I2 imidazoline binding site （IEBS） with ligand is distinct from the catalytic site of MAO-B. Agmatine is the endogenous ligand of receptor I2. Accumulating evidence have revealed that the activation of receptors I2 may produce neuroprotective effects by increasing expression of glial fibriUary acidic protein （GFAP） in astrocytes, inhibiting activity of MAO, reducing calcium overload in cells. Agmatine exerts neuroprotection against ischemia-hypoxia, injury, glutamateinduced neurotoxicity by activating imidazoline receptors, blocking N-methyl-D-aspartate （NMDA） receptor, inhibiting all isoforms of nitric oxide synthase （NOS）, and selectively blocking the voltage-gated calcium channels （VGCC）. It would be expected that agmatine is one of the potential neuroprotective agents.

Enzymatic Synthesis of Agmatine by Immobilized Escherichia coli Cells with Arginine Decarboxylase Activity

A new method for the enzymatic synthesis of agmatine by immobilized Escherichia coli cells with arginine decarboxylase（ADC） activity was established and a series of optimal reaction conditions was set down. The arginine decarboxylase showed the maximum activity when the pyridoxal phosphate（PLP） concentration was 50 mmol/L, pH=7 and 45 °C. The arginine decarboxylase exhibited the maximum production efficiency when the substrate concentration was 100 mmol/L and the reaction time was 15 h. It was also observed that the appropriate concentration of Mg2＋, especially at 0.5 mmol/L promoted the arginine decarboxylase activity; Mn2＋ had little effect on the arginine decarboxylase activity. The inhibition of Cu2＋ and Zn2＋ to the arginine decarboxylase activity was significant. The immobilized cells were continuously used 6 times and the average conversion rate during the six-time usage was 55.6%. The immobilized cells exhibited favourable operational stability. After optimization, the maximally cumulative amount of agmatine could be up to 20 g/L. In addition, this method can also catalyze D,L-arginine to agmatine, leaving the pure optically D-arginine simultaneously. The method has a very important guiding significance to the enzymatic preparation of agmatine.

Synthesis of Tritium and Deuterium Labelled Agmatine

An efficient procedure for the synthesis of agmatine labelled with tritium and deuterium is reported. The final tritiated product 4 was obtained with a specific activity of 40 Ci/mmol and a radiochemical purity of 95%.

Agmatine promotes expression of brain-derived neurotrophic factor in brainstem facial nucleus in the rat facial nerve injury model

BACKGROUND： Studies have shown that agmatine can reduce inhibition of neuronal regeneration by increasing cyclic adenosine monophosphate and brain-derived neurotrophic factor （BDNF） in the hippocampus of morphine-dependent rats. The hypothesis that agmatine exerts similar effects on facial nerve injury deserves further analysis. OBJECTIVE： To study the effects of peritoneal agmatine injection on BDNF levels in the rat brainstem after facial nerve injury. DESIGN, TIME AND SETTING： A controlled animal experiment was performed at the Department of Otolaryngology-Head and Neck Surgery at the Second Affiliated Hospital, Chongqing University of Medical Sciences （Chongqing, China）, between October and December in 2007. MATERIALS： Twenty-four male Sprague-Dawley rats were randomly divided into a control, a lesion, and an agmatine treatment group, with eight rats in each group. Bilateral facial nerve anastomosis was induced in the lesion and agmatine treatment groups, while the control group remained untreated. A rat BDNF Enzyme-linked immunosorbent assay kit was used to measure BDNF levels in the brainstem facial nucleus. METHODS： Starting on the day of lesion, the agmatine group received a peritoneal injection of 100 mg/kg agmatine, once per day, for a week, whereas rats in the lesion group received saline injections. MAIN OUTCOME MEASURES： BDNF levels in the brainstem containing facial nucleus were measured by ELISA. RESULTS： Twenty-four rats were included in the final analysis without any loss. Two weeks after lesion, BDNF levels were significantly higher in the lesion group than in the control group （P 〈 0.01）. A significant increase was noted in the agmatine group compared to the lesion group （P 〈 0.01）. CONCLUSION： Agmatine can substantially increase BDNF levels in the rat brainstem after facial nerve injury.

Agmatine induces gastric protection against ischemic injury by reducing vascular permeability in rats

AIM:To investigate the effect of administration of agmatine(AGM) on gastric protection against ischemia reperfusion(I/R) injury.METHODS:Three groups of rats(6/group);sham,gastric I/R injury,and gastric I/R + AGM(100 mg/kg,i.p.given 15 min prior to gastric ischemia) were recruited.Gastric injury was conducted by ligating celiac artery for 30 min and reperfusion for another 30 min.Gastric tissues were histologically studied and immunostained with angiopoietin 1(Ang-1) and Ang-2.Vascular endothelial growth factor(VEGF) and monocyte chemoattractant protein-1(MCP-1) were measured in gastric tissue homogenate.To assess whether AKt/phosphatidyl inositol-3-kinase(PI3K) mediated the effect of AGM,an additional group was pretreated with Wortmannin(WM)(inhibitor of Akt/PI3K,15 μg/kg,i.p.),prior to ischemic injury and AGM treatment,and examined histologically and immunostained.Another set of experiments was run to study vascular permeability of the stomach using Evan's blue dye.RESULTS:AGM markedly reduced Evan's blue dye extravasation(3.58 ± 0.975 μg/stomach vs 1.175 ± 0.374 μg/stomach,P < 0.05),VEGF(36.87 ± 2.71 pg/100 mg protein vs 48.4 ± 6.53 pg/100 mg protein,P < 0.05) and MCP-1 tissue level(29.5 ± 7 pg/100 mg protein vs 41.17 ± 10.4 pg/100 mg protein,P < 0.01).It preserved gastric histology and reduced congestion.Ang-1 and Ang-2 immunostaining were reduced in stomach sections of AGM-treated animals.The administration of WM abolished the protective effects of AGM and extensive hemorrhage and ulcerations were seen.CONCLUSION:AGM protects the stomach against I/R injury by reducing vascular permeability and inflammation.This protection is possibly mediated by Akt/PI3K.

Agmatine as a novel candidate for rapid-onset antidepressant response

Major depressive disorder(MDD)is a disabling and highly prevalent mood disorder as well as a common cause of suicide.Chronic stress,inflammation,and intestinal dysbiosis have all been shown to play crucial roles in the pathophysiology of MDD.Although conventional antidepressants are widely used in the clinic,they can take weeks to months to produce therapeutic effects.The discovery that ketamine promotes fast and sustaining antidepressant responses is one of the most important breakthroughs in the pharmacotherapy of MDD.However,the adverse psychomimetic/dissociative and neurotoxic effects of ketamine discourage its chronic use.Therefore,agmatine,an endogenous glutamatergic modulator,has been postulated to elicit fast behavioral and synaptogenic effects by stimulating the mechanistic target of rapamycin complex 1 signaling pathway,similar to ketamine.However,recent evidence has demonstrated that the modulation of the NLR family pyrin domain containing 3 inflammasome and gut microbiota,which have been shown to play a crucial role in the pathophysiology of MDD,may also participate in the antidepressant-like effects of both ketamine and agmatine.This review seeks to provide evidence about the mechanisms that may underlie the fast antidepressant-like responses of agmatine in preclinical studies.Considering the anti-inflammatory properties of agmatine,it may also be further investigated as a useful compound for the management of MDD associated with a pro-inflammatory state.Moreover,the fast antidepressant-like response of agmatine noted in animal models should be investigated in clinical studies.

Agmatine reduces nitric oxide synthase expression and peroxynitrite formation in the cerebral cortex in a rat model of transient global cerebral ischemia

Agmatine, an analog of L-arginine, is an endogenous substance synthesized by arginine decarboxylase, which has been shown to possess neuroprotective effects following brain ischemia. Nitric oxide is generated by sequential oxidation of the guanidinium group in L-arginine, and agmatine might protect the brain from ischemic injury by interfering with nitric oxide signaling. This study investigated the effects of agmatine on cerebral cortex neuronal injury following transient global cerebral ischemia and also detected nitric oxide synthase expression and peroxynitrite formation. Results demonstrated that intraperitoneal injection of agmatine in global cerebral ischemia/reperfusion alleviated ischemia/reperfusion-induced cerebral cortical cortex neuronal injury and cellular apoptosis, decreased neuronal and inducible nitric oxide synthase expression at 24, 48, and 72 hours following global cerebral ischemia and reperfusion, and greatly inhibited nitrotyrosine levels, which reflect the amount of peroxynitrite formed. These findings indicated that agmatine alleviates cerebral cortex neuronal injury following global cerebral ischemia and decreases nitric oxide synthase expression and peroxynitrite formation following ischemia/repeffusion.

Agmatine Prevents Adaptation of the Hippocampal Glutamate System in Chronic Morphine-Treated Rats

Abstract Chronic exposure to opioids induces adaptation of glutamate neurotransmission, which plays a crucial role in addiction. Our previous studies revealed that agmatine attenuates opioid addiction and prevents the adaptation of glutamate neurotransmission in the nucleus accumbens of chronic morphine-treated rats. The hippocampus is important for drug addiction; however, whether adaptation of glutamate neurotransmission is modulated by agmatine in the hippocampus remains unknown. Here, we found that continuous pretreatment of rats with ascending doses of morphine for 5 days resulted in an increase in the hip- pocampal extracellular glutamate level induced by nalox- one （2 mg/kg, i.p.） precipitation. Agmatine （20 mg/kg, s.c.） administered concurrently with morphine for 5 days attenuated the elevation of extracellular glutamate levels induced by naloxone precipitation. Furthermore, in the hippocampal synaptosome model, agmatine decreased the release and increased the uptake of glutamate in synapto- somes from chronic morphine-treated rats, which might contribute to the reduced elevation of glutamate levels induced by agrnatine. We also found that expression of the hippocampal NR2B subunit, rather than the NR1 subunit, of N-methyl-D-aspartate receptors （NMDARs） was down-regulated after chronic morphine treatment, and agmatine inhibited this reduction. Taken together, agmatine pre- vented the adaptation of the hippocampal glutamate system caused by chronic exposure to morphine, including mod- ulating extracellular glutamate concentration and NMDAR expression, which might be one of the mechanisms underlying the attenuation of opioid addiction by agmatine.

Functional roles of ornithine decarboxylase and arginine decarboxylase during the peri-implantation period of pregnancy in sheep

Background: Polyamines stimulate DNA transcription and m RNA translation for protein synthesis in trophectoderm cells, as well as proliferation and migration of cells; therefore, they are essential for development and survival of conceptuses(embryo/fetus and placenta). The ovine conceptus produces polyamines via classical and non-classical pathways. In the classical pathway, arginine(Arg) is transformed into ornithine, which is then decarboxylated by ornithine decarboxylase(ODC1) to produce putrescine which is the substrate for the production of spermidine and spermine. In the non-classical pathway, Arg is converted to agmatine(Agm) by arginine decarboxylase(ADC), and Agm is converted to putrescine by agmatinase(AGMAT).Methods: Morpholino antisense oligonucleotides(MAOs) were designed and synthesized to inhibit translational initiation of the m RNAs for ODC1 and ADC, in ovine conceptuses.Results: The morphologies of MAO control, MAO-ODC1, and MAO-ADC conceptuses were normal. Double knockdown of ODC1 and ADC(MAO-ODC1:ADC) resulted in two phenotypes of conceptuses; 33% of conceptuses appeared to be morphological y and functional y normal(phenotype a) and 67% of the conceptuses presented an abnormal morphology and functionality(phenotype b). Furthermore, MAO-ODC1:ADC(a) conceptuses had greater tissue concentrations of Agm,putrescine, and spermidine than MAO control conceptuses, while MAO-ODC1:ADC(b) conceptuses only had greater tissue concentrations of Agm. Uterine flushes from ewes with MAO-ODC1:ADC(a) had greater amounts of arginine, aspartate, tyrosine, citrulline, lysine, phenylalanine, isoleucine, leucine, and glutamine, while uterine flushes of ewes with MAO-ODC1:ADC(b) conceptuses had lower amount of putrescine, spermidine, spermine, alanine, aspartate,glutamine, tyrosine, phenylalanine, isoleucine, leucine, and lysine.Conclusions: The double-knockdown of translation of ODC1 and ADC m RNAs was most detrimental to conceptus development and their production of interferon tau(IFNT). Agm, polyamines, amino acids, and adequate secretion of IFNT are critical for establishment and maintenance of pregnancy during the peri-implantation period of gestation in sheep.