3-hydroxi-anthranilic acid is early expressed in stroke

Abstract

Using an immunohistochemical technique, we have studied the distribution of 3-OH-anthranilic acid (3-HAA) in the rat brain. Our study was carried out in control animals and in rats in which a stroke model (single transient middle cerebral artery occlusion) was performed. A monoclonal antibody directed against 3-HAA was also developed. 3-HAA was exclusively observed in the infarcted regions (ipsilateral striatum/cerebral cortex), 2, 5 and 21 days after the induction of stroke. In control rats and in the contralateral side of the stroke animals, no immunoreactivity for 3-HAA was visualized. Under pathological conditions (from early phases of stroke), we reported for the first time the presence of 3-HAA in the mammalian brain. By double immunohistochemistry, the coexistence of 3-HAA and GFAP was observed in astrocytes. The distribution of 3-HAA matched perfectly with the infarcted regions. Our findings suggest that, in stroke, 3-HAA could be involved in the tissue damage observed in the infarcted regions, since it is well known that 3-HAA exerts cytotoxic effects.

Figure 1.

Low-power magnification (cerebral cortex: 21 days). Photographs were taken using a Leica microscope/ Neurolucida software. A) Section stained with IBA-1, a pan-microglia marker. B) Section stained with 3-HAA. Arrowheads indicate the infarcted region.

Figure 2.

A) Infarcted region (ipsilateral side; cerebral cortex: 21 days) stained with anti-IBA-1. B) Infarcted region; microglia containing IBA-1. C) Infarcted region; coronal contiguous section to that shown in Figure 1A. D) Higher-power magnification of the rectangle showed in Figure 1C; GFAP-immunoreactive astrocytes. E) Infarcted region; coronal contiguous section to that shown in Figure 1C; 3-HAA is observed in astrocytes. F) Higher-power magnification of the region delimited by a rectangle in Figure 1E. L, lateral; V, ventral.

Figure 3.

Infarcted region (ipsilateral side; cerebral cortex: 21 days) stained with anti-IBA-1 (A) or anti-3-HAA (B). Photographs in Figure 2A and B were taken from contiguous sections. The border of the infarcted region is clearly observed in Figure 2B. 3-HAAimmunoreactive astrocytes are exclusively found in the infarcted region. C) Higher-power magnification of the region delimited by a rectangle in Figure 2B. D). Contralateral cerebral cortex of the same section shown in Figure 2B; note the absence of immunoreactivity for 3-HAA. E, F) High-power magnification of the infarcted region; 3-HAA-immunoreactive astrocytes can be observed. L, lateral; M, medial; V, ventral.

Figure 4.

Infarcted region (ipsilateral side; cerebral cortex: 21 days); double-labeling immunohistochemistry. In astrocytes, the coexistence of GFAP (blue labelling, arrowheads) and 3-HAA (brown labelling) is observed.