Functional and pharmacological analysis of agmatine administration in different cerebral ischemia animal models

The development of a whole-cell biosensor enabled the identification of agmatine-producing Hafnia spp. in cheese

Agmatine, the decarboxylation product of arginine, is the precursor of putrescine - a harmful biogenic amine (BA) - that can accumulate in dairy products via bacterial metabolism involving the agmatine deiminase (AGDI) pathway. This first requires agmatine be produced via the decarboxylation of arginine and it remains unknown which microorganisms are responsible for this prior decarboxylation step. In addition, agmatine, as other BA, plays different physiological roles including those of co-transmitter and neuromodulator. Preclinical and clinical studies have shown agmatine to have a neuroprotective effect, rendering it of therapeutic interest being agmatine-producing bacteria proposed as psychobiotics. The identification of BA-producing microorganisms is based on the rise in pH due to the consumption of H+ during such decarboxylation reactions. However, in the detection of agmatine-producing microorganisms in cheese, this would lead to false positives since many bacteria possess arginine deiminase activity; this produces ornithine and ammonium from arginine, which also increases the pH. To overcome this problem, a whole-cell biosensor based on a previously developed agmatine-inducible transcription system was designed, and a protocol optimized for the successful identification of agmatine-producing microorganisms in cheese. The application of this protocol in cheese samples allowed for the isolation of agmatine-producing microorganisms identified as Hafnia spp. and unravels, for first time, the capacity of Hafnia paralvei to produce agmatine. This finding evidence the potential role of Hafnia spp. in putrescine accumulation in dairy products.

Post-stroke effects of IC87201 on neurobehavioral function and brain injuries: A stereological study

Objectives

Stroke is the second leading cause of global death and is characterized by excitotoxic neuronal death caused by NMDA (N-Methyl-D-Aspartate) receptor overactivation. The present study was conducted to investigate the therapeutic potential of IC87201, a novel small molecule interfering with the NMDA receptor intracellular signaling pathway, in reducing the extent of ischemic stroke-induced brain damage.

Materials and Methods

Cerebral ischemia was induced by the middle cerebral artery occlusion (MCAO) method in 24 anesthetized adult male rats for one hour. The animals were randomized into sham, MCAO, MCAO+ DXM (Dextromethorphan hydrobromide monohydrate) as an NMDA antagonist, and MCAO+ IC87201 groups which in the last two groups, DXM (50 mg/kg) and IC87201 (10 mg/kg) were injected intraperitoneally after ischemia. The neurobehavioral scores were appraised for 7 days and after that, brain tissue was appropriately prepared to perform the stereological evaluations.

Results

The administration of IC87201 significantly recovered post-ischemia damages, including neurobehavioral function, reduction of volume of the total hemisphere, cortex, and striatum in rat brain, and the percentage of infarcted areas. Additionally, in the striatum region, IC87201 caused an increase in the total number of neuronal and non-neuronal cells as well as a decrease in the total number of dead cells. Some of these parameters were improved by DXM, but in general, IC87201 outperformed that.

Conclusions

IC87201 was successful in minimizing ischemia-induced damage, especially in the striatal region. In addition, IC87201, as a molecule that acts on the intracellular signaling cascade of the NMDA receptor, performed better than DXM, as an antagonist of this receptor.

Neuroprotection by agmatine: Possible involvement of the gut microbiome?

Agmatine, an endogenous polyamine derived from L-arginine, elicits tremendous multimodal neuromodulant properties. Alterations in agmatinergic signalling are closely linked to the pathogeneses of several brain disorders. Importantly, exogenous agmatine has been shown to act as a potent neuroprotectant in varied pathologies, including brain ageing and associated comorbidities. The antioxidant, anxiolytic, analgesic, antidepressant and memory-enhancing activities of agmatine may derive from its ability to regulate several cellular pathways; including cell metabolism, survival and differentiation, nitric oxide signalling, protein translation, oxidative homeostasis and neurotransmitter signalling. This review briefly discusses mammalian metabolism of agmatine and then proceeds to summarize our current understanding of neuromodulation and neuroprotection mediated by agmatine. Further, the emerging exciting bidirectional links between agmatine and the resident gut microbiome and their implications for brain pathophysiology and ageing are also discussed.

Effects of imidazoline agents in a rat conditioned place preference model of addiction

Agmatine (AG), idazoxan (IDZ), and efaroxan (EFR) are imidazoline receptor ligands with beneficial effects in central nervous system disorders. The present study aimed to evaluate the interaction between AG, IDZ, and EFR with an opiate, tramadol (TR), in a conditioned place preference (CPP) paradigm. In the experiment, we used five groups with 8 adult male Wistar rats each. During the condition session, on days 2, 4, 6, and 8, the rats received the drugs (saline, or TR, or IDZ and TR, or EFR and TR, or AG and TR) and were placed in their least preferred compartment. On days 1, 3, 5, and 7, the rats received saline in the preferred compartment. In the preconditioning, the preferred compartment was determined. In the postconditioning, the preference for one of the compartments was reevaluated. TR increased the time spent in the non-preferred compartment. AG decreased time spent in the TR-paired compartment. EFR, more than IDZ, reduced the time spent in the TR-paired compartment, but without statistical significance. AG reversed the TR-induced CPP, while EFR and IDZ only decreased the time spent in the TR-paired compartment, without statistical significance.