Agmatine reduces infarct area in a mouse model of transient focal cerebral ischemia and protects cultured neurons from ischemia-like injury

Agmatine attenuates stress- and lipopolysaccharide-induced fever in rats

Physiological stress evokes a number of responses, including a rise in body temperature, which has been suggested to be the result of an elevation in the thermoregulatory set point. This response seems to share similar mechanisms with infectious fever. The aim of the present study was to investigate the effect of agmatine on different models of stressors [(restraint and lipopolysaccharide (LPS)] on body temperature. Rats were either restrained for 4 h or injected with LPS, both of these stressors caused an increase in body temperature. While agmatine itself had no effect on body temperature, treatment with agmatine (20, 40, 80 mg/kg intraperitoneally) dose dependently inhibited stress- and LPS-induced hyperthermia. When agmatine (80 mg/kg) was administered 30 min later than LPS (500 microg/kg) it also inhibited LPS-induced hyperthermia although the effect became significant only at later time points and lower maximal response compared to simultaneous administration. To determine if the decrease in body temperature is associated with an anti-inflammatory effect of agmatine, the nitrite/nitrate levels in plasma was measured. Agmatine treatment inhibited LPS-induced production of nitrates dose dependently. As an endogenous molecule, agmatine has the capacity to inhibit stress- and LPS-induced increases in body temperature.

Reduction in levels of matrix metalloproteinases and increased expression of tissue inhibitor of metalloproteinase-2 in response to mild hypothermia therapy in experimental stroke

OBJECT

Mild hypothermia is a robust neuroprotectant, and the results of prospective clinical trials have indicated that it may improve neurological outcome in certain instances. One aspect of this protection has been associated with the prevention of blood-brain barrier (BBB) disruption. Matrix metalloproteinases (MMPs) have been implicated in BBB disruption because they can degrade the extracellular matrix. In this study the authors explored the relationship between hypothermia and MMPs and whether BBB preservation resulting from mild hypothermia therapy is due to alterations in MMP expression.

METHODS

Rats were subjected to middle cerebral artery occlusion for 2 hours; the animals were maintained in a state of normothermia or mild hypothermia (33 degrees C) immediately after the onset of ischemia. The animals' brains were collected 2, 6, and 24 hours after ischemia began. Contrast-enhanced T1-weighted magnetic resonance imaging was performed at 24 hours to assess the extent of BBB disruption. Consistent with prior reports, areas of BBB disruption detected on T1-weighted images were smaller in the brains of rats maintained in a state of hypothermia (normothermia group 8.6 +/- 3% of the brain; hypothermia group 0.2 +/-0.1% of the brain; p < 0.01). Expression of both MMP-2 and MMP-9 at the transcriptional and translational levels was reduced in hypothermic brains at 6 hours and 24 hours after ischemic injury. Matrix metalloproteinase-9 was primarily localized to cells of monocytic origin but was also observed in neurons and astrocytes. Matrix metalloproteinase-2 was found in some neurons and astrocytes but not in inflammatory cells. In addition, hypothermia increased the levels of the endogenous MMP inhibitor, tissue inhibitor of metalloproteinases-2.

CONCLUSIONS

The authors conclude that mild hypothermia attenuates BBB disruption, decreases MMP expression, and suppresses MMP activity.

Agmatine reduces extracellular glutamate during pentylenetetrazole-induced seizures in rat brain: a potential mechanism for the anticonvulsive effects

Glutamate has been implicated in the initiation and spread of seizure activity. Agmatine, an endogenous neuromodulator, is an antagonist of NMDA receptors and has anticonvulsive effects. Whether agmatine regulate glutamate release, as measured by in vivo microdialysis, is not known. In this study, we used pentylenetetrazole (PTZ)-induced seizure model to determine the effect of agmatine on extracellular glutamate in rat brain. We also determined the time course and the amount of agmatine that reached brain after peripheral injection. After i.p. injection of agmatine (50 mg/kg), increase of agmatine in rat cortex and hippocampus was observed in 15 min with levels returning to baseline in one hour. Rats, naïve and implanted with microdialysis cannula into the cortex, were administered PTZ (60 mg/kg, i.p.) with prior injection of agmatine (100 mg/kg, i.p.) or saline. Seizure grades were recorded and microdialysis samples were collected every 15 min for 75 min. Agmatine pre-treatment significantly reduced the seizure grade and increased the onset time. The levels of extracellular glutamate in frontal cortex rose two- to three-fold after PTZ injection and agmatine significantly inhibited this increase. In conclusion, the present data suggest that the anticonvulsant activity of agmatine, in part, could be related to the inhibition glutamate release.

Effect of C-reactive protein on gene expression in vascular endothelial cells

C-reactive protein (CRP) is significantly associated with the risk of ischemic cardiovascular disease in epidemiological studies. To explore if CRP has a functional role, we investigated its effect on the gene expression profile of vascular endothelial cells. Human vascular endothelial cells (human umbilical vein endothelial cells and human aortic endothelial cells) were incubated with CRP at various concentrations (0–10 μg/ml). Microarray analysis showed that a total of 11 genes increased (IL-8, core promoter element binding protein, activin A, monocyte chemoattractant protein 1, Exostoses 1, Cbp/p300-interacting transactivator with Glu/Asp-rich COOH-terminal domain 2, plasminogen activator inhibitor 1, fibronectin-1, gravin, connexin43, and sortilin-related receptor-1) and 6 genes decreased (methionine adenosyltransferase 2A, tryptophan-rich basic protein, reticulocalbin 1, membrane-associated RING-CH protein VI, cytoplasmic dynein1, and annexin A1) by more than twofold for their mRNA levels. IL-8 was the most significantly upregulated gene (13.6-fold), which demonstrated a clear dose- and time-dependent pattern revealed by quantitative real-time PCR. Cell adhesion assay showed that CRP enhanced the monocyte adhesion to endothelial cell monolayer by 2-fold ( P < 0.01), which was partially blocked by an anti-IL-8 antibody (34.2% inhibition, P < 0.01). Inhibition of ERK MAPK pathway using U0126 prevented CRP-induced IL-8 upregulation, and Western blot analysis revealed a rapid activation of ERK1/2 after CRP stimulation. These data showed that CRP can significantly influence gene expressions in vascular endothelium. The CRP-responsive genes suggested that CRP may have a broad functional role in cell growth and differentiation, vascular remodeling and solid tumor development.