Developmental Maturation and Alpha-1 Adrenergic Receptors-Mediated Gene Expression Changes in Ovine Middle Cerebral Arteries

Abstract

The Alpha Adrenergic Signaling Pathway is one of the chief regulators of cerebrovascular tone and cerebral blood flow (CBF), mediating its effects in the arteries through alpha1-adrenergic receptors (Alpha1AR). In the ovine middle cerebral artery (MCA), with development from a fetus to an adult, others and we have shown that Alpha1AR play a key role in contractile responses, vascular development, remodeling, and angiogenesis. Importantly, Alpha1AR play a significant role in CBF autoregulation, which is incompletely developed in a premature fetus as compared to a near-term fetus. However, the mechanistic pathways are not completely known. Thus, we tested the hypothesis that as a function of maturation and in response to Alpha1AR stimulation there is a differential gene expression in the ovine MCA. We conducted microarray analysis on transcripts from MCAs of premature fetuses (96-day), near-term fetuses (145-day), newborn lambs, and non-pregnant adult sheep (2-year) following stimulation of Alpha1AR with phenylephrine (a specific agonist). We observed several genes which belonged to pro-inflammatory and vascular development/angiogenesis pathway significantly altered in all of the four age groups. We also observed age-specific changes in gene expression-mediated by Alpha1AR stimulation in the different developmental age groups. These findings imply complex regulatory mechanisms of cerebrovascular development.

Figure 1

Flowchart demonstrates the number of genes altered in middle cerebral arteries at different developmental ages.

Figure 2

Bar graphs demonstrating mRNA expression of upregulated genes by quantitative real-time PCR in response to Alpha1AR specific agonist phenylephrine (PHE) and Alpha1AR specific antagonist (Prazosin). N = 4 for each experiment and * denotes P < 0.05.

Figure 3

Bar graphs demonstrating mRNA expression of downregulated genes by quantitative real-time PCR in response to Alpha1AR specific agonist phenylephrine (PHE) and Alpha1AR specific antagonist (Prazosin). N = 4 for each experiment and * denotes P < 0.05.

Figure 4

Venn diagram demonstrating the number of (A) genes altered (B) pathways altered and (C) upstream regulators altered in response to Alpha1AR activation in middle cerebral arterial segments from sheep at different developmental age groups.

Figure 5

Bar graph demonstrating canonical pathways commonly altered in response to Alpha1AR activation in middle cerebral arterial segments from all four developmental age group studied.

Figure 6

Bar graphs demonstrating canonical pathways altered in response to Alpha1AR activation in middle cerebral arterial segments exclusively in (A) premature fetus and (B) near-term fetus.

Figure 7

Overall schematic demonstrating pathways altered commonly in all four groups and in age specific manner.