The microbial metabolite agmatine acts as an FXR agonist to promote polycystic ovary syndrome in female mice.

Polycystic ovary syndrome (PCOS), an endocrine disorder afflicting 6-20% of women of reproductive age globally, has been linked to alterations in the gut microbiome. We previously showed that in PCOS, elevation of Bacteroides vulgatus in the gut microbiome was associated with altered bile acid metabolism. Here we show that B. vulgatus also induces a PCOS-like phenotype in female mice via an alternate mechanism independent of bile acids. We find that B. vulgatus contributes to PCOS-like symptoms through its metabolite agmatine, which is derived from arginine by arginine decarboxylase. Mechanistically, agmatine activates the farnesoid X receptor (FXR) pathway to subsequently inhibit glucagon-like peptide-1 (GLP-1) secretion by L cells, which leads to insulin resistance and ovarian dysfunction. Critically, the GLP-1 receptor agonist liraglutide and the arginine decarboxylase inhibitor difluoromethylarginine ameliorate ovarian dysfunction in a PCOS-like mouse model. These findings reveal that agmatine-FXR-GLP-1 signalling contributes to ovarian dysfunction, presenting a potential therapeutic target for PCOS management.

Efficacy of Agmatine Treatment in Experimental Acute Pancreatitis Rat Model.

BACKGROUND/AIMS: Acute pancreatitis which is characterized by pancreatic inflammation can sometimes be difficult to treat because of limited therapeutic options. The purpose of the study was to assess the effects of agmatine in the acute pancreatitis experimental rat model. MATERIALS AND METHODS: An acute pancreatitis model was created with the administration of cerulein in 40 female Sprague-Dawley rats. Agmatine was administered as a protective agent at 5 mg/kg (low dose) and 10 mg/kg (high dose). The rats were divided into 5 groups, each with 8 rats: group 1 (acute pancreatitis); group 2 (acute pancreatitis+low-dose agmatine 5 mg/kg); group 3 (acute pancreatitis+high-dose agmatine 10 mg/kg); group 4 (placebo, acute pancreatitis+saline); and group 5 (sham and saline infusion). All rats were sacrificed 24 hours after the last injection, and the levels of superoxide dismutase, interleukin-1 beta, and tumor necrosis factor-alpha were assessed in blood samples collected via cardiac puncture. Histopathological examination was performed by a pathologist, who was blind to the groups, according to the Schoenberg's pancreatitis scoring index. RESULTS: The amylase (16.67 and 37.89 U/L), glutathione peroxidase (13.62 and 18.44 ng/mL), tumor necrosis factor-α (39.68 and 64 ng/mL), interleukin-1 (484.73 and 561.83 pg/mL), and transforming growth factor-ß (110.52 and 126.34 ng/L) levels were significantly lower and superoxide dismutase (1.29 and 0.98 ng/L) and malondialdehyde (0.99 and 0.96 nmol/mL) levels were significantly higher in group 3 compared to group 1 (P < .05). Moreover glutathione peroxidase, tumor necrosis factor-α, and transforming growth factor-ß levels were lower, and malondialdehyde levels were higher in the group 3 compared to group 2 (P < .05). Although the Schoenberg's pancreatitis scoring index was not significantly different between the high- and low-dose treatment groups, rats who received high-dose treatment had significantly lower scores compared to those with acute pancreatitis group. CONCLUSION: This is the first study that evaluated the efficacy of agmatine in an experimental model of acute pancreatitis. Agmatine, an anti-inflammatory and antioxidant agent, had a protective effect in an experimental rat model of acute pancreatitis.

Agmatine prevents the memory impairment and the dysfunction of hippocampal GSK-3ß and ERK signaling induced by aluminum nanoparticle in mice.

The growing usage of aluminum nanoparticles (Al-NP) and their exposure may influence body function. Considering the proposed relationship between Al and the pathogenesis of Alzheimer's disease and the concern about the effect of this nanoparticle on brain health and cognitive function, the use of neuroprotective agents might be helpful. According to the reported neuroprotective effects of agmatine, in the present study, the possible protective effect of agmatine was assessed in mice model of Al-NP-induced memory impairment. In addition, due to the roles of hippocampal Glycogen synthase kinase-3 beta (GSK-3ß) and ERK signaling in memory and its disorders, these pathways were also investigated. Al-NP (10 mg/kg/p.o.) with/without agmatine (5 or 10 mg/kg/i.p.) was administered to adult male NMRI mice for 5 days. Novel object recognition (NOR) test session was used to assess cognitive function. Following the behavioral assessments, the hippocampi were used to determine the phosphorylated and total levels of GSK-3ß and ERK as well as GAPDH using western blot analysis. The results showed that Al-NP impaired NOR memory in mice while agmatine 10 mg/kg prevented the memory deficit induced by Al-NP. Furthermore, Al-NP activated GSK-3ß as well as ERK signals within the hippocampus while agmatine prevented the effects of Al-NP on GSK-3ß and ERK signals within the hippocampus. Besides supporting the neuroprotective effects of agmatine, these findings suggest the possibility of the connection of hippocampal GSK-3ß and ERK signaling in the neuroprotective effect of this polyamine against Al-NP.

Agmatine improves liver function, balance performance, and neuronal damage in a hepatic encephalopathy induced by bile duct ligation.

INTRODUCTION: In the current study, we investigate whether oral administration of agmatine (AGM) could effectively reduce motor and cognitive deficits induced by bile duct ligation (BDL) in an animal model of hepatic encephalopathy (HE) through neuroprotective mechanisms. METHODS: The Wistar rats were divided into four groups: sham, BDL, BDL+ 40 mg/kg AGM, and BDL+ 80 mg/kg AGM. The BDL rats were treated with AGM from 2 weeks after the surgery for 4 consecutive weeks. The open field, rotarod, and wire grip tests were used to assess motor function and muscle strength. The novel object recognition test (NOR) was performed to evaluate learning and memory. Finally, blood samples were collected for the analysis of the liver markers, the animals were sacrificed, and brain tissues were removed; the CA1 regions of the hippocampus and cerebellum were processed to identify apoptosis and neuronal damage rate using caspase-3 immunocytochemistry and Nissl staining. RESULTS: The serological assay results showed that BDL severely impaired the function of the liver. Based on histochemical findings, BDL increased the neuronal damage in CA1 and Purkinje cells, whereas apoptosis was significantly observed only in the cerebellum. AGM treatment prevented the increase of serum liver enzymes, balance deficits, and neuronal damage in the brain areas. Apoptosis partially decreased by AGM, and there were no differences in the performance of animals in different groups in the NOR. CONCLUSIONS: The study suggests AGM as a potential treatment candidate for HE because of its neuroprotective properties and/or its direct effects on liver function.

Cholestasis-Associated Pulmonary Inflammation, Oxidative Stress, and Tissue Fibrosis: The Protective Role of the Biogenic Amine Agmatine.

INTRODUCTION: Cholestasis is the stoppage of bile flow, leading to the accumulation of potentially cytotoxic bile components in the liver. These cytotoxic molecules affect many organs. Cholestasis-induced lung injury is a severe complication that could lead to tissue fibrosis and respiratory distress. Substantial evidence indicates the role of oxidative stress and inflammatory response in the pathogenesis of cholestasis-associated pulmonary damage. Agmatine (AGM; 1-amino-4-guanidinobutane) is a biogenic amine endogenously synthesized in the human body. This amine provides potent anti-inflammatory and antioxidant properties. METHODS: In the current study, a series (six C57BL/6J male mice/group) of bile duct-ligated (BDL) animals were monitored at scheduled intervals (7, 14, and 28 days after the BDL operation) to ensure inflammatory response in their lung tissue (by analyzing their bronchoalveolar lavage fluid [BALF]). It was found that the level of inflammatory cells, pro-inflammatory cytokines, and IgG in the BALF reached their maximum level on day 28 after the BDL surgery. Therefore, other research groups were selected as follows: 1) Sham-operated (2.5 mL/kg normal saline, i.p., for 28 consecutive days), 2) BDL, 3) BDL + AGM (1 mg/kg/day, i.p., for 28 consecutive days), and 4) BDL + AGM (10 mg/kg/day, i.p., for 28 consecutive days). Then, the BALF was monitored at scheduled time intervals (7, 14, and 28 days post-BDL). RESULTS: It was found that pro-inflammatory cytokines (TNF-α, IL-6, and IL-1ß), bile acids, bilirubin, and inflammatory cells (monocytes, neutrophils, and lymphocytes) were significantly increased in the BALF of BDL mice. Moreover, biomarkers of oxidative stress were significantly increased in the pulmonary tissue of cholestatic animals. Lung tissue histopathological changes, tissue collagen deposition, and increased TGF-ß were also detected. It was found that AGM significantly ameliorated cholestasis-induced lung injury. CONCLUSION: The effects of AGM on inflammatory indicators, oxidative stress biomarkers, and tissue fibrosis seem to play a pivotal role in its protective properties.

Agmatine prevents the manifestation of impulsive burying and depression-like behaviour in progesterone withdrawn female rats.

Premenstrual dysphoric disorder (PMDD) is characterized by various physical and affective symptoms, including anxiety, irritability, anhedonia, social withdrawal, and depression. The present study investigated the role of the agmatinergic system in animal model of progesterone withdrawal in female rats. Chronic progesterone exposure of female rats for 21 days and its abrupt withdrawal showed enhanced marble burying, increased immobility time, and reduced no. of entries in open arm as compared to control animals. The progesterone withdrawal-induced enhanced marble burying anxiety and immobility time was significantly attenuated by agmatine (5-20 mg/kg, i.p.), and its endogenous modulators like L-arginine (100 mg/kg, i.p.), amino-guanidine (25 mg/kg, i.p.) and arcaine (50 mg/kg, i.p.) by their once-daily administration from day 14-day 21 of the protocol. We have also analysed the levels of agmatine, progesterone, and inflammatory cytokines in the hippocampal region of progesterone withdrawn rats. There was a significant decline in agmatine and progesterone levels and an elevation in cytokine levels in the hippocampal region of progesterone withdrawn rats compared to the control animals. In conclusion, the present studies suggest the importance of the endogenous agmatinergic system in progesterone withdrawal-induced anxiety-like and depression-like behaviour. The data also projects agmatine as a potential therapeutic target for the premenstrual dysphoric disorder.

Long-term reversal of chronic pain behavior in rodents through elevation of spinal agmatine.

Chronic pain remains a significant burden worldwide, and treatments are often limited by safety or efficacy. The decarboxylated form of L-arginine, agmatine, antagonizes N-methyl-d-aspartate receptors, inhibits nitric oxide synthase, and reverses behavioral neuroplasticity. We hypothesized that expressing the proposed synthetic enzyme for agmatine in the sensory pathway could reduce chronic pain without motor deficits. Intrathecal delivery of an adeno-associated viral (AAV) vector carrying the gene for arginine decarboxylase (ADC) prevented the development of chronic neuropathic pain as induced by spared nerve injury in mice and rats and persistently reversed established hypersensitivity 266 days post-injury. Spinal long-term potentiation was inhibited by both exogenous agmatine and AAV-human ADC (hADC) vector pre-treatment but was enhanced in rats treated with anti-agmatine immunoneutralizing antibodies. These data suggest that endogenous agmatine modulates the neuroplasticity associated with chronic pain. Development of approaches to access this inhibitory control of neuroplasticity associated with chronic pain may yield important non-opioid pain-relieving options.

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.

Agmatine mitigates palmitate (PA)-induced mitochondrial and metabolic dysfunction in microvascular endothelial cells.

Agmatine is an arginine metabolite that has neuroprotective capacity. Recently, it has been found to ameliorate atherosclerosis progression in rabbits. However, further molecular mechanisms of its anti-atherosclerotic properties remain unclear. High plasma levels of free fatty acids (FFAs) are an important risk factor for atherosclerosis due to their detrimental effects on vascular endothelial cells (ECs). Here, we used palmitate (PA), a kind of FFA, to induce endothelial dysfunction in human microvascular endothelial cells (HMECs) to determine the possible biological functions of agmatine. We found that PA caused ECs dysfunction in HMEC-1 cells, decreased cell viability, and elevated lactate dehydrogenase (LDH) release which could be reversed by agmatine treatment. Agmatine also improved the nitric oxide (NO) production and endothelial nitric oxide synthase (eNOS) activity in PA-induced HMEC-1 cells. The PA-caused mitochondrial dysfunction of HMEC-1 cells was diminished after agmatine treatment, as proven by the increased intracellular Adenosine Triphosphate (ATP) level, decreased mitochondrial reactive oxygen species (ROS) level, and increased mitochondrial oxygen consumption rate (OCR). Further, agmatine could alleviate PA-caused lipid accumulation with increased levels of Triglyceride (TG) and total cholesterol (TC) in HMEC-1 cells. Furthermore, Western blot analysis revealed that agmatine administration markedly decreased the expression levels of phosphorylated-AMP-activated protein kinase α (p-AMPKα), p-protein kinase B (p-AKT), and p-eNOS in PA-induced HMEC-1 cells. Inhibition of AMPK by compound C reversed the protective effects of agmatine on PA-induced HMEC-1 cells. Taken together, we hypothesize that agmatine mitigated PA-induced HMEC-1 cell dysfunction by alleviating mitochondrial and metabolic dysfunction via the AMPK/PI3K/Akt/eNOS signaling pathway.

Protective Effect of Agmatine Against Cisplatin- Induced Cellular Apoptosis in an Auditory Cell Line.

BACKGROUND: The aims of this study were to evaluate the protective effects of agmatine against cisplatin-induced cellular apoptosis in an audi- tory cell line and to prove the protective mechanism of agmatine. METHODS: The House Ear Institute-Organ of Corti 1 cells were co-treated with agmatine at different concentrations and 15 µM of cisplatin for 48 hours. Cell viability and proliferation were measured. Annexin V-fluorescein isothiocyanate /propidium iodide staining was performed to analyze apoptosis. The levels of intracellular reactive oxygen species were measured using flow cytometry. The expression of BCL2-associated X protein and the enzymatic activity of caspase-3 was measured to examine the pathway of apoptosis induction. RESULTS: In normal conditions, the maximal protective effect occurred with 10 mM of agmatine. However, in the presence of cisplatin, the maximal protective effect was observed from 8 mM of agmatine. Thus, 8 mM was chosen as the ideal agmatine concentration for the analysis of protective effects against cisplatin-induced cytotoxicity. Agmatine exerted a significant protective effect against 15 µM of cisplatin when applied for 48 hours and reduced the proportion of necrotic and late apoptotic cells. Agmatine did not significantly reduce the cisplatin-induced increase in reactive oxygen species but decreased the expression of BCL2-associated X protein and the activity of caspase-3. CONCLUSION: Agmatine protected against cisplatin-induced cellular apoptosis in an auditory cell line. These effects were mediated by the pro- tection of mitochondrial function and inhibition of apoptosis.

Agmatine Mitigates Inflammation-Related Oxidative Stress in BV-2 Cells by Inducing a Pre-Adaptive Response.

Neuroinflammation and microglial activation, common components of most neurodegenerative diseases, can be imitated in vitro by challenging microglia cells with Lps. We here aimed to evaluate the effects of agmatine pretreatment on Lps-induced oxidative stress in a mouse microglial BV-2 cell line. Our findings show that agmatine suppresses nitrosative and oxidative burst in Lps-stimulated microglia by reducing iNOS and XO activity and decreasing O2- levels, arresting lipid peroxidation, increasing total glutathione content, and preserving GR and CAT activity. In accordance with these results, agmatine suppresses inflammatory NF-kB, and stimulates antioxidant Nrf2 pathway, resulting in decreased TNF, IL-1 beta, and IL-6 release, and reduced iNOS and COX-2 levels. Together with increased ARG1, CD206 and HO-1 levels, our results imply that, in inflammatory conditions, agmatine pushes microglia towards an anti-inflammatory phenotype. Interestingly, we also discovered that agmatine alone increases lipid peroxidation end product levels, induces Nrf2 activation, increases total glutathione content, and GPx activity. Thus, we hypothesize that some of the effects of agmatine, observed in activated microglia, may be mediated by induced oxidative stress and adaptive response, prior to Lps stimulation.

Agmatine Alleviates Cisplatin-Induced Ototoxicity by Activating PI3K/AKT Signaling Pathway.

Cisplatin-induced ototoxicity can be partially attributed to excessive reactive oxygen species (ROS) production, and agmatine is well-known for the activation of the phosphoinositide-3-kinase (PI3K)/protein kinase B (AKT) pathway to inhibit ROS production. Whether agmatine could be used to alleviate cisplatin-induced ototoxicity is investigated. Cisplatin-exposed House Ear Institute-Organ of Corti 1 (HEI-OC1) cells and cochlear explants showed increased ROS production detected by 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining and decreased cell viability detected by Cell Counting Kit-8 (CCK-8) or Myosin 7a staining, which could be reversed by the agmatine pretreatment. Cisplatin intraperitoneally injected C57BL/6 mice demonstrated damaged auditory function as indicated by distortion products otoacoustic emissions (DPOAEs) and auditory brainstem response (ABR) assays, and trans-tympanically administrated agmatine in the left ears could partly prevent the auditory function loss. Mechanistically, downregulated B-cell lymphoma 2 (Bcl-2) expression, upregulated Bcl2-associated x (Bax) expression, and diminished p-PI3K and p-AKT expression were detected in cisplatin-exposed HEI-OC1 cells and cochlear explants, which could be prevented by the pretreatment with agmatine. Our investigation demonstrates that agmatine pretreatment could alleviate cisplatin-induced ototoxicity with the activation of PI3K/AKT signaling pathway.

Agmatine prevents development of tolerance to anti-nociceptive effect of ethanol in mice.

Drug tolerance is directly correlated with drug abuse and physical dependence. The development of tolerance is manifested as the decline in pharmacological responses of drugs following repeated administration of the constant dose. The present study evaluated the effect of agmatine in ethanol-induced anti-nociception and tolerance in the tail-flick assay in mice. In an acute protocol, ethanol (1 and 2 g/kg, i.p. [intraperitoneally]) and agmatine (20 and 40 µg/mouse, i.c.v. [intracerebroventricularly]) produced significant analgesic effects in mice, as was evident from the increased baseline tail-flick latency when tested 20 minutes after their administration. Agmatine in a per se non-effective dose (5 µg/mouse, i.c.v.), L-arginine (40 µg/mouse, i.c.v.), and arcaine (25 µg/mouse, i.c.v.) significantly potentiated the anti-nociceptive effect of ethanol. Blood ethanol analysis showed no significant differences in blood ethanol concentration between ethanol/saline- and ethanol/agmatine-treated mice, suggesting that the effects of agmatine were not due to any possible effects on the pharmacokinetics of ethanol. In a separate study, mice were injected with ethanol (2 g/kg, i.p., 12%) or saline (1 mL/kg, i.p.) once daily for 9 days. On days 1, 3, 5, 7, and 9 of the experiment, they were subjected to the tail-flick test. Agmatine (5-20 µg/mouse, i.c.v.), L-arginine (40 µg/mouse, i.c.v.), arcaine (25 µg/mouse, i.c.v.), aCSF (2 µL/mouse, i.c.v.), or saline (1 mL/kg, i.p.) was administered daily prior to the first daily ethanol or saline injections, and reaction latencies were determined in the tail-flick assay. Injections of agmatine, L-arginine, and arcaine prevented the development of tolerance to ethanol-induced analgesia. Given that agmatine and its endogenous modulation can prevent tolerance to the anti-nociceptive effects of ethanol, these data suggest it as a possible new therapeutic strategy for the treatment of alcohol use disorder and associated complications.

Progesterone and interferon tau regulate expression of polyamine enzymes during the ovine peri-implantation period†.

Progesterone (P4) and interferon tau (IFNT) are important for establishment and maintenance of pregnancy in ruminants. Agmatine and polyamines (putrescine, spermidine, and spermine) have important roles in the survival, growth, and development of mammalian conceptuses. This study tested the hypothesis that P4 and/or IFNT stimulate the expression of genes and proteins involved in the metabolism and transport of polyamines in the ovine endometrium. Rambouillet ewes (n = 24) were surgically fitted with intrauterine catheters on Day 7 of the estrous cycle. They received daily intramuscular injections of 50 mg P4 in corn oil vehicle and/or 75-mg progesterone receptor antagonist (RU486) in corn oil vehicle from Days 8-15, and twice daily intrauterine injections (25 µg/uterine horn/day) of either control serum proteins (CX) or IFNT from Days 11-15, resulting in four treatment groups: (i) P4 + CX; (ii) P4 + IFNT; (iii) RU486 + P4 + CX; or (iv) RU486 + P4 + IFNT. On Day 16, ewes were hysterectomized. The total amounts of arginine, citrulline, ornithine, agmatine, and putrescine in uterine flushings were affected (P < 0.05) by P4 and/or IFNT. P4 increased endometrial expression of SLC22A2 (P < 0.01) and SLC22A3 (P < 0.05) mRNAs. IFNT affected endometrial expression of MAT2B (P < 0.001), SAT1 (P < 0.01), and SMOX (P < 0.05) mRNAs, independent of P4. IFNT increased the abundance of SRM protein in uterine luminal (LE), superficial glandular (sGE), and glandular epithelia (GE), as well as MAT2B protein in uterine LE and sGE. These results indicate that P4 and IFNT act synergistically to regulate the expression of key genes required for cell-specific metabolism and transport of polyamines in the ovine endometrium during the peri-implantation period of pregnancy.

The effects of subchronic agmatine on passive avoidance memory, anxiety-like behavior and hippocampal Akt/GSK-3ß in mice.

Agmatine, a polyamine derived from l-arginine, has been suggested to modulate memory. However, the available evidence regarding the effect of agmatine on the memory of intact animals is contradictory. This study aimed to assess the dose-response effect of subchronic agmatine on passive avoidance memory and anxiety-like parameters of elevated plus maze in adult intact mice. Furthermore, considering the roles of Akt/GSK-3ß signaling pathway in memory and Alzheimer's disease, the hippocampal contents of phosphorylated and total forms of Akt and GSK-3ß proteins were determined using the western blot technique. Agmatine was administered intraperitoneally at the doses of 10, 20, 30, 40 and 80 mg/kg/daily to adult male NMRI mice for 10 days after which the behavioral assessments were performed. Upon completion of the passive avoidance test, the hippocampi were removed for western blot analysis to detect the phosphorylated and total levels of Akt and GSK-3ß proteins. Results showed the biphasic effect of agmatine on passive avoidance memory; in lower doses (10, 20 and 30 mg/kg), agmatine impaired memory whereas in higher ones (40 and 80 mg/kg) improved it. Though, agmatine in none of the doses affected animals' anxiety-like parameters in an elevated plus maze. Moreover, the memory-improving doses of agmatine augmented Akt/GSK-3ß pathway. This study showed the biphasic effect of agmatine on passive avoidance memory and an augmentation of hippocampal Akt/GSK-3ß signaling pathway following the memory-improving doses of this polyamine.

Retinoprotective effect of agmatine in streptozotocin-induced diabetic rat model: avenues for vascular and neuronal protection : Agmatine in diabetic retinopathy.

Diabetic retinopathy (DR) is the most common diabetic neurovascular complication, and the leading cause of preventable blindness among working-age individuals. Recently, agmatine, the endogenous decarboxylated L-arginine, has gained attention as a pleiotropic agent that modulates the diabetes-associated decline in quality of life, and exhibited varied protective biological effects. Diabetes was induced by a single streptozotocin (STZ, 50 mg/kg, i.p.) injection. When diabetes was verified, the animals were randomly allocated into three groups (16 rat each); diabetic, agmatine-treated diabetic (1 mg/kg, daily, for 12 weeks), and control group. Blood glucose homeostasis, retinal redox status, apoptotic parameters, nitric oxide synthase (NOS), nitric oxide (NO), vascular endothelial growth factor (VEGF), glutamate, glutamine, glutamine synthase (GS) activity, nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB), and mitogen-activated protein kinase (MAPKs) pathways were assayed biochemically. Retinal vascular permeability was measured. Retinal morphology was evaluated by hematoxylin and eosin staining. Retinal N-methyl-D-aspartic acid receptor1 (NMDAR1) and glutamate aspartate transporter (GLAST) mRNA were quantified. Glucose transporter 1, pro-caspase3, and glial fibrillary acidic protein (GFAP) expression were quantified by immunohistochemistry. Chronic agmatine treatment abrogated STZ-induced retinal neurodegeneration features including gliosis, and neuronal apoptosis, restored retinal vascular permeability, mostly through antioxidant, anti-apoptotic capacity, abolishing glutamate excitotoxicity, modulating the activity of NMDARs, MAPKs/NFκB, and NOS/NO pathways. By restoring the molecular and functional background of retinal neurovascular homeostatic balance, agmatine would be appropriate therapeutic option acting upstream of the DR, impeding its progression.

Agmatine potentiates antidepressant and synaptic actions of ketamine: Effects on dendritic arbors and spines architecture and Akt/S6 kinase signaling.

We investigated the ability of agmatine to potentiate the antidepressant-like and synaptic effects of ketamine in mice. Agmatine (0.1 and 1 mg/kg, p.o.) and ketamine (1 and 10 mg/kg, i.p.) produced an antidepressant-like effect in the tail suspension test. The combination of agmatine (0.01 mg/kg, p.o.) and ketamine (0.1 mg/kg, i.p.), at subthreshold doses, produced an antidepressant-like effect 1 h, 24 h and 7d after treatment. Western blot analysis from prefrontal cortex tissue showed that the combined treatment, after 1 h, increased p70S6K and GluA1, and reduced synapsin 1 phosphorylation. Additionally, after 24 h, Akt, p70S6K, GluA1, and synapsin 1 phosphorylation; and PSD95 immunocontent increased (which persisted for up to 7d). Dendritic architecture analysis of the prefrontal cortex revealed that the combined treatment improved dendritic arbor complexity (after 24 h, up to 7d), and increased spine density (after 1 h, up to 24 h). Morphometric analysis revealed a filopodia-shaped dendrite spine upregulation after 1 h. A predominance of stubby, mushroom, branched and filopodia; and a reduction in thin protrusions were observed after 24 h. Finally, mushroom-shaped dendritic spines predominance increased after 7d. Agmatine potentiated ketamine's antidepressant, and dendritic arbors and spines remodeling effects in a time-dependent manner. Our data indicate Akt/p70S6K signaling as a likely target for these effects.

Involvement of hippocampal agmatine in ß1-42 amyloid induced memory impairment, neuroinflammation and BDNF signaling disruption in mice.

Alzheimer's disease (AD) is a chronic and progressive neurodegenerative disorder characterized by abnormal accumulation of extracellular ß-amyloid (Aß) plaques and neuronal damage. The present study investigated the effect of chronic intra-hippocampal agmatine administration on ß-Amyloid (Aß) induced memory impairment in mice. Aß1-42 peptide injected mice demonstrated impairment of cognitive abilities evaluated as reference memory error and working memory error in radial arm maze (RAM) and decreased exploration time for novel object as well as recognition index in novel object recognition (NOR) test along with elevation in Aß1-42 peptide, ß-Site APP cleaving enzyme 1 (BACE 1), microtubule-associated protein tau (MAPt), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and reduction in neprilysin and brain derived neurotrophic factor (BDNF) immunocontent within hippocampus and prefrontal cortex. Importantly, this was associated with a reduction in the agmatine levels following Aß1-42 peptide administration. Chronic administration of agmatine from day 8-27, prevented the memory impairment in mice and normalized the neurochemical alteration within prefrontal cortex and hippocampus induced by Aß1-42 peptide administration. However, it did not modulate the amyloid precursor protein and BACE expression. This study suggests that agmatine improves learning and memory impairment possibly through the down regulation of neuroinflammatory pathways in AD.

Agmatine Attenuates Liver Ischemia Reperfusion Injury by Activating Wnt/ß-catenin Signaling in Mice.

BACKGROUND: Liver ischemia reperfusion injury (LIRI) is a common problem during surgical procedures of the liver. It causes severe inflammatory responses and cell death, eventually leading to serious liver damage. Agmatine (AGM) is an endogenous polyamine with analgesic, anti-inflammatory, and antiapoptotic effects. However, it is still unknown whether AGM can protect the liver from damage caused by LIRI. METHODS: For the in vivo experiments, a mouse model of partial warm hepatic ischemia reperfusion was established using C57BL/6J mice and then serum transaminase concentrations were analyzed. Histopathology was used to evaluate the degree of liver injury and quantitative real-time PCR was used to measure the amount of inflammatory cytokines. For the in vitro experiments, a cellular model of cobalt chloride (CoCl2)-induced hypoxia was established using AML12 cells. Flow cytometry was performed to measure the apoptosis levels. Western blotting analysis was conducted to measure the levels of proteins involved in apoptosis and Wnt/ß-catenin signaling. We also chose 2 inhibitors of the Wnt/ß-catenin signaling to elucidate the relationship between AGM and the Wnt/ß-catenin signaling. RESULTS: AGM showed protective effects against LIRI-induced liver damage, inflammatory responses, and cell apoptosis along with alleviation of CoCl2-induced hepatocyte injury. AGM activated the Wnt/ß-catenin signaling pathway during LIRI and CoCl2-induced hepatocyte injury; however, when the Wnt/ß-catenin pathway was inhibited, the protective effects of AGM declined. CONCLUSIONS: AGM showed protective effects against LIRI by activating the Wnt/ß-catenin signaling pathway.