Reduction of Gstm1 Expression in the Stroke-Prone Spontaneously Hypertension Rat Contributes to Increased Oxidative Stress

Abstract

Abstract-Human essential hypertension is a classic example of a complex, multifactorial, polygenic disease with a substantial genetic influence in which the underlying genetic components remain unknown. The stroke-prone spontaneously hypertension rat (SHRSP) is a well-characterized experimental model for essential hypertension and endothelial dysfunction. Previous work, identified glutathione S-transferase type 1, a protein involved in detoxification of reactive oxygen species, as a positional and functional candidate gene. Quantitative real-time polymerase chain reaction showed a highly significant, 4-fold reduction of glutathione S-transferase type 1 mRNA expression in 5-and 16-week-old SHRSP compared with the congenic and normotensive Wistar Kyoto rats. This suggests that differential expression is not attributable to long-term changes in blood pressure. DNA sequencing identified one coding single nucleotide polymorphism (R202H) and multiple single nucleotide polymorphisms in the promoter region. mRNA expression changes were reflected at the protein level, with significant reductions in the SHRSP glutathione S-transferase type 1. Protein was colocalized with aquaporin 2 to the principle cells of the renal collecting ducts.Coupled to significant increases in nitrotyrosine levels in the kidney, this suggests a pathophysiological role of this protein in hypertension and oxidative stress. Similar processes may underlie oxidative stress in the vasculature. Key Words: rats, stroke-prone SHR Ⅲ hypertension, genetic Ⅲ gene expression Ⅲ oxidative stress H uman essential hypertension is a classic example of a complex, multifactorial, polygenic disease with a substantial genetic influence in which the underlying genetic components remain unknown. [1][2][3][4] The methodological difficulties in studying the genetic determinants of hypertension have given a major impetus for development of similar but inherently simpler paradigms in rodent models of genetic hypertension that remain under complex control. 5-7 Genetic heterogeneity can be reduced by the use of inbred strains with complete control over environmental influences. Moreover, the ability to produce genetic crosses and analyze large numbers of progeny facilitate genetic analysis, including genetic dissection of complex phenotypes, gene-gene and gene-environment interactions. 8 -10 The stroke-prone spontaneously hypertensive rat (SHRSP) is a well-characterized experimental model for essential hypertension and endothelial dysfunction. 11-13 Genome-wide scans performed on several rat crosses have identified quantitative trait loci (QTLs), which are involved in blood pressure regulation. 5 However, these represent large chromosomal regions and contain too many putative candidate genes to pursue classic positional cloning strategies. More recently, generation of congenic strains in which blood pressure QTLs from a normotensive strain have been introgressed into a hypertensive background has allowed genetic dissection of QTLs in hypertensive strains. [13][14][15][16] ...

An association between resistant hypertension and the null GSTM1 genotype

“…1 It has been recently observed that stroke-prone spontaneously hypertensive rats had significantly reduced levels of glutathione S-transferase (GST) (m type 1) M1 expression. 7 Lower glutathione Stransferase m type 1 (GSTM1) expression levels were associated with increased superoxide levels and reduced nitric oxide bioavailability in the rat renal medulla and cortex. 7 It has been suggested but not shown that human participants who have a GSTM1 null genotype may be prone to atherosclerosis and endothelial dysfunction and subsequent development of hypertension.…”

“…7 Lower glutathione Stransferase m type 1 (GSTM1) expression levels were associated with increased superoxide levels and reduced nitric oxide bioavailability in the rat renal medulla and cortex. 7 It has been suggested but not shown that human participants who have a GSTM1 null genotype may be prone to atherosclerosis and endothelial dysfunction and subsequent development of hypertension. 7 We therefore hypothesized that variations in human GSTM1 may determine susceptibility to hypertension and resistant primary hypertension.…”

“…7 It has been suggested but not shown that human participants who have a GSTM1 null genotype may be prone to atherosclerosis and endothelial dysfunction and subsequent development of hypertension. 7 We therefore hypothesized that variations in human GSTM1 may determine susceptibility to hypertension and resistant primary hypertension.…”

The genetics of cardiovascular disease

“…Amongst the classes of GST enzymes the mu class is particularly involved in detoxification of free radicals. GSTM enzymes protect against oxidative stress, and or reduced expression of Gstm1 has been found to be associated with hypertension in rats [23,34,35]. This text box shows major mechanisms but is by no means a comprehensive overview of the pathogenesis of hypertension.…”

“…First, WTCCC was the first large-scale genome 24 scan using dense SNP markers across the genome. Previous genome scans were limited by the 25 in SHRSP and chromosome 2 congenic strains [34,35], GSTM genes were subject to association 1 studies in humans [39][40][41] due to the fundamental role of the oxidative stress pathway in 2 cardiovascular pathophysiology [42,43]. While there is agreement on the involvement of genetic 3 variants of GSTMs in the development of cancer [44,45], studies on the role of GSTMs in 4 cardiovascular diseases are less consistent [40,41].…”