Molecular basis for impaired collateral artery growth in the spontaneously hypertensive rat: insight from microarray analysis

Analysis of global gene expression in mesenteric control and collateral arteries was used to investigate potential molecules, pathways, and mechanisms responsible for impaired collateral growth in the Spontaneously Hypertensive Rat ( SHR ). A fundamental difference was observed in overall gene expression pattern in SHR versus Wistar Kyoto ( WKY ) collaterals; only 6% of genes altered in collaterals were similar between rat strains. Ingenuity ® Pathway Analysis ( IPA ) identified major differences between WKY and SHR in networks and biological functions related to cell growth and proliferation and gene expression. In SHR control arteries, several mechano‐sensitive and redox‐dependent transcription regulators were downregulated including JUN (−5.2×, P  = 0.02), EGR 1 (−4.1×, P  = 0.01), and NF ĸB1 (−1.95×, P  = 0.04). Predicted binding sites for NF ĸB and AP ‐1 were present in genes altered in WKY but not SHR collaterals. Immunostaining showed increased NF ĸB nuclear translocation in collateral arteries of WKY and apocynin‐treated SHR , but not in untreated SHR . si RNA for the p65 subunit suppressed collateral growth in WKY , confirming a functional role of NF kB. Canonical pathways identified by IPA in WKY but not SHR included nitric oxide and renin–angiotensin system signaling. The angiotensin type 1 receptor ( AGTR 1) exhibited upregulation in WKY collaterals, but downregulation in SHR ; pharmacological blockade of AGTR 1 with losartan prevented collateral luminal expansion in WKY . Together, these results suggest that collateral growth impairment results from an abnormality in a fundamental regulatory mechanism that occurs at a level between signal transduction and gene transcription and implicate redox‐dependent modulation of mechano‐sensitive transcription factors such as NF ĸB as a potential mechanism.