Measurement of oxidative stress in stroke-prone spontaneously hypertensive rat brain usingin vivoelectron spin resonance spectroscopy

Abstract

A number of researchers have reported that free radicals generated in the brain are involved in various brain dysfunctions, including ischemia-reperfusion injury, brain tumors, and neurodegenerative diseases. It has been reported that the spin probe MC-PROXYL can penetrate the blood-brain barrier and can be useful for evaluating oxidative stress in the brain. Preliminary comparisons were made by ESR imaging of the heads of live mice and isolated rat brains using the spin probe MC-PROXYL and the blood-brain-barrier impermeable probe carbamoyl-PROXYL. The results showed that MC-PROXYL, but not carbamoyl-PROXYL, was widely distributed in the brain. These methods were also applied for the imaging of brains from stroke-prone spontaneously hypertensive rats (SHRSPs). The rapid decay of 2D ESR images of MC-PROXYL in isolated SHRSP-brain was observed, compared to Wistar-Kyoto rats (WKYs), using the ESR imaging system. Furthermore, we provide evidence, by using L-band ESR non-invasively, that the decay rate of MC-PROXYL in the head region is faster in live SHRSPs than in live WKYs. Taken together, the high oxidative stress sustained by oxygen radical generation in SHRSPs may cause the alteration of MC-PROXYL metabolism in the brain. Our results suggest that in vivo ESR could be applied to the assessment of antioxidant effects on oxidative stress in the brain in animal disease models, such as the SHRSP.

Assessment of Oxidative Stress in the Spontaneously Hypertensive Rat Brain Using Electron Spin Resonance (ESR) Imaging and in Vivo L-Band ESR

“…1-3). We previously confirmed that the decay rate of MC-PROXYL in the isolated brains of SHRSP, a hypertensive reference strain (38) in which cerebral ischemia-reperfusion is known to occur due to oxidative stress (39,40), was also significantly faster than in the brain of WKY (29). Thus, the present study demonstrated a difference in the degree of oxidative stress between SHR and SHRSP brains.…”

“…ESR imaging is particularly useful for determining the in vivo spatial distribution of free radicals in animals. It has been suggested that MC-PROXYL is a suitable spin probe for the study of free radical reactions in the brain by in vivo ESR detection (23,29,30,33,34). Our data show that MC-PROXYL, but not carbamoyl-PROXYL, is well distributed in the brain and that the ESR signal decays in a time-dependent fashion.…”

“…It has also been shown by in vivo fluorescence microscopy that blood vessels of SHR generate excessive amounts of O2 (28). We previously measured oxidative stress in the brains of stroke prone SHR (SHRSP) in comparison with normal male Wistar Kyoto rats (WKY) (29). However, we were unable to detect a difference in oxidative stress in the brain among SHR, WKY and SHRSP.…”

“…3. Further, the K1 of SHRSP was significantly faster than in SHR, suggesting that the oxidative stress in SHR was only moderate compared to that in SHRSP, the latter being the oxidative stress model reported in our previous study (29).…”

“…Only the right side of the brain was observed in 2D (data not shown), further indicating that MC-PROXYL is distributed in the brain. It has also been reported that MC-PROXYL is a suitable spin probe for the study of free radical reactions in the rodent brain by in vivo ESR detection (23,29,30,33,34). Thus, these methods were also used to compare images from the brains of WKY, SHR, and SHRSP.…”