Temporal mRNA Expression of Purinergic P2 Receptors in the Brain Following Cerebral Ischemia and Reperfusion: Similarities and Distinct Variations Between Rats and Mice

Abstract

Purinergic P2 receptors are crucial in energy utilization and cellular signaling, making them key targets for stroke therapies. This study examines the temporal mRNA expression of all P2 receptors in rats and mice. Both species exhibited a common subset of P2X and P2Y receptors with elevated expression following cerebral ischemia and reperfusion (I/R), highlighting conserved mechanisms across these species. The receptors with upregulated expression in both species were P2X3, P2X4, P2X7, P2Y2, and P2Y6. While these similarities were observed, notable differences in receptor expression emerged between rats and mice. Rats exhibited a broader receptor profile, with five additional receptors (P2X1, P2Y1, P2Y12, P2Y13, and P2Y14) significantly upregulated compared to only two receptors (P2X2 and P2Y4) in mice, highlighting species-specific regulation of receptor expression distinct from the shared receptors. Following cerebral I/R, P2Y12 was the most upregulated receptor in rats, while P2Y2 was the most upregulated in mice. These findings reveal both conserved and species-specific changes in P2 receptor expression following cerebral I/R. Targeting purinergic receptors, particularly those conserved and upregulated in response to stroke, may represent a promising therapeutic approach.

Keywords: brain; expression; ischemia; purinergic; receptor; reperfusion; stroke.

Figure 1

Relationship between the mRNA expression of purinergic P2X and P2Y receptors in the brains of rats and mice under baseline conditions. (A) The column scatterplots show the quantified baseline mRNA expression for various purinergic P2X receptors (P2X1 through P2X7) and P2Y receptors (P2Y1 through P2Y14) in mice expressed as fold change relative to their expression in rats. * p < 0.05, ** p < 0.01, *** p < 0.001. ns—not significant. (B) The scatterplots show the log2-transformed relative expression (group means; n = 5–6) for each of the studied P2X receptors (left panel) and P2Y receptors (right panel) in rats versus mice. In the plots, less negative log2 values (i.e., closer to −12) indicate higher expression, while more negative values indicate lower expression. The green line in each plot represents the line of best fit. Pearson’s correlation analysis of the log2-transformed relative expression values between rats and mice indicated no significant relationship for P2X receptors (r = 0.279, p = 0.545), but a strong positive linear relationship was observed for P2Y receptors (r = 0.923, p = 0.003). Baseline expression values in both species were obtained from sham animals euthanized on day 7 post-surgery.

Figure 2

Temporal mRNA expression of purinergic P2X receptors in the ipsilateral brains of rats and mice following ischemic stroke. The column scatterplots show the quantified mRNA expression of purinergic P2X receptors (P2X1 through P2X7) as fold changes relative to day-7 sham in the ischemic brains of stroke-induced rats and mice. Animals were subjected to the right middle cerebral artery occlusion (2 h for rats and 1 h for mice) and euthanized at predetermined time points following stroke (days 1, 3, 5, and 7). * p < 0.05; ** p < 0.01; *** p < 0.001; **** p < 0.0001 vs. sham group.

Figure 3

Summary of purinergic P2X receptor upregulation in rodents following ischemic stroke. (A) The bar graphs depict the highest observed mRNA expression levels (group means) for each purinergic P2X receptor at one of the tested time points in the ischemic brains of stroke-induced rats and mice. The horizontal lines in both bar graphs indicate the threshold above which increases in mRNA expression are considered biologically significant, provided they also reach statistical significance. (B) The Venn diagram illustrates the similarities and differences among the upregulated P2X receptors that demonstrate both biological and statistical significance at one or more of the tested time points (days 1, 3, 5, and 7 post-ischemia) in the ipsilateral brains of stroke-induced rats and mice.

Figure 4

Temporal mRNA expression of purinergic P2Y receptors in the ipsilateral brains of rats and mice following ischemic stroke. The column scatterplots show the quantified mRNA expression of purinergic P2Y receptors (P2Y1 through P2Y14) as fold changes relative to day-7 sham in the ipsilateral brains of rats and mice. Animals were subjected to the right middle cerebral artery occlusion (2 h for rats and 1 h for mice) and euthanized at predetermined time points following stroke (days 1, 3, 5, and 7). * p < 0.05; ** p < 0.01; *** p < 0.001; **** p < 0.0001 vs. sham group.

Figure 5

Summary of purinergic P2Y receptor upregulation in rodents following ischemic stroke. (A) The bar graphs depict the highest observed mRNA expression levels (group means) for each of the purinergic P2Y receptors at one of the tested time points in the ischemic brains of stroke-induced rats and mice. The horizontal lines in both bar graphs indicate the threshold above which increases in mRNA expression are considered biologically significant, provided they also reach statistical significance. (B) The Venn diagram illustrates the similarities and differences among the upregulated purinergic P2Y receptors that demonstrate both biological and statistical significance at one or more of the tested time points (days 1, 3, 5, and 7 post-ischemia) in the ipsilateral brains of stroke-induced rats and mice.

Figure 6

Schematic illustration of experimental design. Rats and mice were subjected to transient right middle cerebral artery occlusion (MCAO). Animals from designated experimental groups were euthanized at various time points (post-ischemic days 1, 3, 5, and 7), and their ipsilateral brains were collected and processed for real-time PCR analysis. This figure was created with BioRender.com (accessed on 29 September 2024) under a paid subscription.