Agmatine attenuates brain edema through reducing the expression of aquaporin-1 after cerebral ischemia

Abstract

Brain edema is frequently shown after cerebral ischemia. It is an expansion of brain volume because of increasing water content in brain. It causes to increase mortality after stroke. Agmatine, formed by the decarboxylation of L-arginine by arginine decarboxylase, has been shown to be neuroprotective in trauma and ischemia models. The purpose of this study was to investigate the effect of agmatine for brain edema in ischemic brain damage and to evaluate the expression of aquaporins (AQPs). Results showed that agmatine significantly reduced brain swelling volume 22 h after 2 h middle cerebral artery occlusion in mice. Water content in brain tissue was clearly decreased 24 h after ischemic injury by agmatine treatment. Blood-brain barrier (BBB) disruption was diminished with agmatine than without. The expressions of AQPs-1 and -9 were well correlated with brain edema as water channels, were significantly decreased by agmatine treatment. It can thus be suggested that agmatine could attenuate brain edema by limiting BBB disruption and blocking the accumulation of brain water content through lessening the expression of AQP-1 after cerebral ischemia.

Figure 1

Brain edema and infarct volume on cerebral ischemia. Agmatine reduced infarct volume and brain swelling after ischemic injury. (A) Serial coronal sections (1.5 mm of thickness) of mouse brain stained with 2% triphenyl tetrazolium chloride solution. (B) Graph of brain swelling percent (%) 22 h after 2 h MCAO (^*P<0.05; ^**P<0.01 versus EC). Data were expressed as mean±s.d. Gray bar, noninfarct area; black bar, infarct area; EC (n=7), experimental control group; NC (n=4), normal control group; Agm (n=9), agmatine treatment group

Figure 2

Brain water content on cerebral ischemia. Brain water content was analyzed as a measure of brain edema of the ischemic hemisphere 22 h after 2 h MCAO. Agmatine decreased the total water content of ischemic injured brain to normal level (^**P<0.01 versus IS of EC; +P<0.05 and ++P<0.01 versus LS of EC). Data are expressed as mean±s.d. EC (n=3), experimental control group; NC (n=5), normal control group; Agm (n=4), agmatine treatment group; IS, ipsilateral ischemic side; LS, contralateral ischemic side.

Figure 3

Macrographs of AQP-1 immunofluorescence in the ischemic injured brain 22 h after 2 h MCAO with or without agmatine. Blood vessel marked with factorVIII (red) was stained with AQP-1 (green) in cortex (A) and striatum (B) of experimental control (EC), but was not merged with AQP-1 (green) in cortex (A) and striatum (B) of agmatine treatment group (Agm). AQP-1 (green) was boldly detected at blood vessel of the choroid plexus of ipsilateral side (Ipsi) in experimental control (EC) but was not in agmatine treatment group (Agm) (C). Scale bar is 50 μm. Contra, contralateral side.

Figure 4

The expression of AQPs in the ischemic injured brain 22 h after 2 h MCAO with or without agmatine by immunoblotting. Optical densites (OD) of AQPs-1, -4, and -9 are expressed as the band density of each group. Data are expressed as mean±s.d. Agmatine treatment significantly decreased the expression of AQPs-1 and -9 compared with experimental control (^*P<0.05 versus EC). NC (n=3), normal control group; EC (n=4), experimental control group; Agm (n=3), agmatine treatment group.