- Email: [email protected]
Arachidonic acid cytochrome P450 4F2 in hypertension: what can we learn from a transgenic mouse model??
co m m e nta r y
clinical indices of renal injury are manifest, one has to look for other VEGF parameters. As it is possible that the serum level of VEGF increases before the renal content of VEGF decreases, this could allow precise timing of intervention. It is important to test this hypothesis in the clinical setting. Understanding the complex regulation of VEGF metabolism in lupus patients could provide physicians with invaluable information for the treatment or prevention of lupus nephritis. DISCLOSURE The author declared no competing interests. REFERENCES 1.
Yung S, Chan TM. Anti-DNA antibodies in the pathogenesis of lupus nephritis — the emerging mechanisms. Autoimmun Rev 2008; 7: 317–321. 2. Belmont HM, Abramson SB, Lie JT. Pathology and pathogenesis of vascular injury in systemic lupus erythematosus. Interactions of inflammatory cells and activated endothelium. Arthritis Rheum 1996; 39: 9–22. 3. Isenberg DA, Manson JJ, Ehrenstein MR et al. Fifty years of anti-ds DNA antibodies: are we approaching journey’s end? Rheumatology 2007; 46: 1052–1056. 4. Daniel L, Sichez H, Giorgi R et al. Tubular lesions and tubular cell adhesion molecules for the prognosis of lupus nephritis. Kidney Int 2001; 60: 2215–2221. 5. Avihingsanon Y, Benjachat T, Tassanarong A et al. Decreased renal expression of vascular endothelial growth factor in lupus nephritis is associated with worse prognosis. Kidney Int 2009; 75: 1340–1348. 6. Robak E, Sysa-Jedrzejewska A, Robak T. Vascular endothelial growth factor and its soluble receptors VEGFR-1 and VEGFR-2 in the serum of patients with systemic lupus erythematosus. Mediators Inflamm 2003; 12: 293–298. 7. Izui S, Lambert PH, Miescher PA. In vitro demonstration of a particular affinity of glomerular basement membrane and collagen for DNA. A possible basis for a local formation of DNA-anti-DNA complexes in systemic lupus erythematosus. J Exp Med 1976; 144: 428–443. 8. Simon M, Grone HJ, Johren O et al. Expression of vascular endothelial growth factor and its receptors in human renal ontogenesis and in adult kidney. Am J Physiol Renal Physiol 1995; 268: F240–F250. 9. Feliers D, Duraisamy S, Barnes JL et al. Translational regulation of vascular endothelial growth factor expression in renal epithelial cells by angiotensin II. Am J Physiol Renal Physiol 2005; 288: F521–F529. 10. Yung S, Tsang RC, Sun Y et al. Effect of human anti-DNA antibodies on proximal renal tubular epithelial cell cytokine expression: implications on tubulointerstitial inflammation in lupus nephritis. J Am Soc Nephrol 2005; 16: 3281–3294. 11. Lindenmeyer MT, Kretzler M, Boucherot A et al. Interstitial vascular rarefaction and reduced VEGF-A expression in human diabetic nephropathy. J Am Soc Nephrol 2007; 18: 1765–1776. Kidney International (2009) 75
see original article on page 1288
Arachidonic acid cytochrome P450 4F2 in hypertension: what can we learn from a transgenic mouse model? Yiqiang Cai1 The cytochrome P450-derived 20-hydroxyeicosatetraenoic acid (20-HETE) has known function that plays opposite roles in blood pressure: prohypertensive and antihypertensive. Liu et al. report that the CYP4F2 transgene, driven under an exogenous promoter, increases 20-HETE production and is associated with increased blood pressure in vivo. This study provides evidence for the first time that overexpression of P450 4F2 enzyme results in higher production of 20-HETE, which promotes hypertension. The significance of this transgenic mouse model is further discussed. Kidney International (2009) 75, 1253–1254. doi:10.1038/ki.2009.82
Arachidonic acid (AA) has long been found to be metabolized by cyclooxygenase and lipoxygenase enzymes to prostaglandins, prostacyclin, thromboxane, leukotrienes, and 5-, 12-, and 15-hydroxyeicosatetraenoic acid (HETE). Recently, it was found that AA is also metabolized by the -hydroxylase cytochrome P450 (CYP) enzymes to form epoxyeicosatrienoic acids, dihydroxyeicosatetraenoic acids, 19-HETE, 20-HETE, and other forms of HETE. The metabolites of AA generated by the P450 enzymes have been found to play important roles in the regulation of vascular tone in renal, cerebral, coronary, and skeletal muscle arterioles and in pulmonary circulation. 1,2 More than 500 CYP genes have been identified; among them, CYP4F2, CYP4A11, and CYP4F3B are thought to be the major 1Section of Nephrology, Department of Internal
Medicine, Yale University School of Medicine, New Haven, Connecticut, USA Correspondence: Yiqiang Cai, Section of Nephrology, Department of Internal Medicine, Yale University School of Medicine, 300 Cedar Street, New Haven, CT 6510, USA. E-mail: [email protected]
genes involved in metabolizing AA to form 20-HETE.1,2 20-HETE is a potent constrictor of small arteries and arterioles; however, in the kidney, 20-HETE also regulates tubular sodium reabsorption in the proximal tubule, as well as in the thick ascending limb of Henle’s loop via inhibition of Na + -K + -ATPase activities or Na + -K + -2Cl– cotransport. Therefore, the influence of 20-HETE on blood pressure remains difficult to predict: it could play either a prohypertensive or an antihypertensive role, depending on its action as a vasoconstrictor or a sodium reabsorption inhibitor in renal tubules. 1,3 In addition, studies in human and animal models also suggest diverse effects of CYP gene function on blood pressure. In humans, functional polymorphism analysis demonstrated that diverse consequences resulted from genetic polymor phism: t he CYP4F2 GA / AA genotype was significantly associated with an increase in both 20-HETE excretion and systolic blood pressure, whereas the CYP4A11 CC/TC genotype was significantly associated with a reduction in 20-HETE excretion but 1253
com m enta r y
CYP4F2 ↑
20-HETE ↑
?
?
Elevated blood pressure
Figure 1 | Model of CPY4F2 gene function. Increased expression of CYP4F2 that caused increased production of 20-HETE was associated with elevated blood pressure. However, the mechanism(s) underlying the link between increased 20-HETE and hypertension, and whether other factors contributed to the elevated blood pressure, remain unknown.
was not associated with changes in blood pressure. 3 Furthermore, the CYP4F2 M433 variant caused decreased production of 20-HETE.4 On the other hand, the transfer of the CYP4A region of chromosome 5 from Lewis to Dahl salt-sensitive rats increased production of 20-HETE but attenuated the development of hypertension and renal disease. 5 These data combined indicate that further investigation is needed to better understand the overall effect of the functioning of CYP genes and 20HETE on blood pressure in vivo. Liu and colleagues6 (this issue) established a novel transgenic mouse model in which the human CYP4F2 gene was overexpressed under regulation of the mouse kidney androgen-regulated protein promoter. The authors showed overexpression of the CYP4F2 transgene in proximal tubules of the kidney but also in other organs. They found increased -hydroxylase activities and renal 20-HETE production in transgenic mice. Of importance, among three transgenic mouse lines, two were found to have significantly elevated 1254
systolic blood pressure that was positively ass o ciated with increas ed CYP4F2 expression and 20-HETE production. This study provides a novel gain-of-function mouse model showing for the first time that increased expression of the wild-type CYP4F2 gene results in increased production of 20-HETE and a positive association with elevated blood pressure in vivo . Considering the many potential effects that 20-HETE may have on blood pressure, the study by Liu et al. 6 suggests that increased production of 20-HETE has a prohypertensive role in vivo . In addition, previous studies showed that functional polymorphism of CYP4F2 could result in either increased or d e c re as e d 2 0 - H E T E pro du c t i on depending on the type of variation.3,4 The study by Liu et al. 6 suggests that the change in 20-HETE production, which links to a CYP4F2 polymorphism, may result from changes in the activity of the P450 4F2 enzyme. Currently, the mechanism or mechanisms that link CYP4F2 -derived increased 20-HETE production and elevated blood pressure remain unclear in this transgenic model (Figure 1). It was reported for the first time by Ward et al. that urinary 20-HETE is associated with endothelial dysfunction in humans.7 Moreover, an experimental study in rats further revealed that vascular P450 4A expression and 20-HETE synthesis contribute to endothelial dysfunction in androgen-induced hypertension. 8 Whether endothelial dysfunction resulted from the P450 4F2-derived increased 20-HETE production in the mouse model of Liu et al.6 remains undetermined. It is noteworthy that one transgenic mouse line in their study, F0-6, has slightly higher urinary 20-HETE than the transgenic line F0-56, which has elevated blood pressure but lacks significant elevated blood pressure in male mice. Whether this phenomenon results from genetic variation or reflects involvement of other factors such as endothelial dysfunction in the hypertensive phenotype remains to be determined. Another possibility is that increased CYP4F2 gene expression may also result in
increased production of 19-HETE, another metabolite of AA, which may act as a competitive antagonist of the inhibitory effects of 20-HETE on sodium reabsorption in the kidney. Further studies to address the above possibilities would help in understanding the mechanism(s) that links increased expression of CYP4F2 and 20-HETE production to elevated blood pressure in this transgenic model. Finally, transgene expression driven by the exogenous promoter might not faithfully recapitulate the native distribution profile of the target gene, which may result in functional consequences not seen in wild-type circumstances. In this regard, transgenic mouse overexpression of a bacterial artificial chromosome (BAC)CYP4F2 gene that carries the endogenous promoter may serve as a faithful model to establish the link between P450 4F2-derived 20-HETE production and changes in blood pressure in vivo. DISCLOSURE The author declared no competing interests.
REFERENCES 1.
2.
3.
4.
5.
6.
7.
8.
Roman RJ. P-450 metabolites of arachidonic acid in the control of cardiovascular function. Physiol Rev 2002; 82: 131–185. Miyata N, Roman RJ. Role of 20hydroxyeicosatetraenoic acid (20-HETE) in vascular system. J Smooth Muscle Res 2005; 41: 175–193. Ward NC, Tsai IJ, Barden A et al. A single nucleotide polymorphism in the CYP4F2 but not CYP4A11 gene is associated with increased 20-HETE excretion and blood pressure. Hypertension 2008; 51: 1393–1398. Stec DE, Roman RJ, Flasch A et al. Functional polymorphism in human CYP4F2 decreases 20HETE production. Physiol Genomics 2007; 30: 74–81. Williams JM, Sarkis A, Hoagland KM et al. Transfer of the CYP4A region of chromosome 5 from Lewis to Dahl S rats attenuates renal injury. Am J Physiol Renal Physiol 2008; 295: F1764–F1777. Liu X, Zhao Y, Wang L et al. Overexpression of cytochrome P450 4F2 in mice increases 20-hydroxyeicosatetraenoic acid production and arterial blood pressure. Kidney Int 2009; 75: 1288–1296. Ward NC, Rivera J, Hodgson J et al. Urinary 20hydroxyeicosatetraenoic acid is associated with endothelial dysfunction in humans. Circulation 2004; 110: 438–443. Singh H, Cheng J, Deng H et al. Vascular cytochrome P450 4A expression and 20-hydroxyeicosatetraenoic acid synthesis contribute to endothelial dysfunction in androgen-induced hypertension. Hypertension 2007; 50: 123–129. Kidney International (2009) 75
clinical indices of renal injury are manifest, one has to look for other VEGF parameters. As it is possible that the serum level of VEGF increases before the renal content of VEGF decreases, this could allow precise timing of intervention. It is important to test this hypothesis in the clinical setting. Understanding the complex regulation of VEGF metabolism in lupus patients could provide physicians with invaluable information for the treatment or prevention of lupus nephritis. DISCLOSURE The author declared no competing interests. REFERENCES 1.
Yung S, Chan TM. Anti-DNA antibodies in the pathogenesis of lupus nephritis — the emerging mechanisms. Autoimmun Rev 2008; 7: 317–321. 2. Belmont HM, Abramson SB, Lie JT. Pathology and pathogenesis of vascular injury in systemic lupus erythematosus. Interactions of inflammatory cells and activated endothelium. Arthritis Rheum 1996; 39: 9–22. 3. Isenberg DA, Manson JJ, Ehrenstein MR et al. Fifty years of anti-ds DNA antibodies: are we approaching journey’s end? Rheumatology 2007; 46: 1052–1056. 4. Daniel L, Sichez H, Giorgi R et al. Tubular lesions and tubular cell adhesion molecules for the prognosis of lupus nephritis. Kidney Int 2001; 60: 2215–2221. 5. Avihingsanon Y, Benjachat T, Tassanarong A et al. Decreased renal expression of vascular endothelial growth factor in lupus nephritis is associated with worse prognosis. Kidney Int 2009; 75: 1340–1348. 6. Robak E, Sysa-Jedrzejewska A, Robak T. Vascular endothelial growth factor and its soluble receptors VEGFR-1 and VEGFR-2 in the serum of patients with systemic lupus erythematosus. Mediators Inflamm 2003; 12: 293–298. 7. Izui S, Lambert PH, Miescher PA. In vitro demonstration of a particular affinity of glomerular basement membrane and collagen for DNA. A possible basis for a local formation of DNA-anti-DNA complexes in systemic lupus erythematosus. J Exp Med 1976; 144: 428–443. 8. Simon M, Grone HJ, Johren O et al. Expression of vascular endothelial growth factor and its receptors in human renal ontogenesis and in adult kidney. Am J Physiol Renal Physiol 1995; 268: F240–F250. 9. Feliers D, Duraisamy S, Barnes JL et al. Translational regulation of vascular endothelial growth factor expression in renal epithelial cells by angiotensin II. Am J Physiol Renal Physiol 2005; 288: F521–F529. 10. Yung S, Tsang RC, Sun Y et al. Effect of human anti-DNA antibodies on proximal renal tubular epithelial cell cytokine expression: implications on tubulointerstitial inflammation in lupus nephritis. J Am Soc Nephrol 2005; 16: 3281–3294. 11. Lindenmeyer MT, Kretzler M, Boucherot A et al. Interstitial vascular rarefaction and reduced VEGF-A expression in human diabetic nephropathy. J Am Soc Nephrol 2007; 18: 1765–1776. Kidney International (2009) 75
see original article on page 1288
Arachidonic acid cytochrome P450 4F2 in hypertension: what can we learn from a transgenic mouse model? Yiqiang Cai1 The cytochrome P450-derived 20-hydroxyeicosatetraenoic acid (20-HETE) has known function that plays opposite roles in blood pressure: prohypertensive and antihypertensive. Liu et al. report that the CYP4F2 transgene, driven under an exogenous promoter, increases 20-HETE production and is associated with increased blood pressure in vivo. This study provides evidence for the first time that overexpression of P450 4F2 enzyme results in higher production of 20-HETE, which promotes hypertension. The significance of this transgenic mouse model is further discussed. Kidney International (2009) 75, 1253–1254. doi:10.1038/ki.2009.82
Arachidonic acid (AA) has long been found to be metabolized by cyclooxygenase and lipoxygenase enzymes to prostaglandins, prostacyclin, thromboxane, leukotrienes, and 5-, 12-, and 15-hydroxyeicosatetraenoic acid (HETE). Recently, it was found that AA is also metabolized by the -hydroxylase cytochrome P450 (CYP) enzymes to form epoxyeicosatrienoic acids, dihydroxyeicosatetraenoic acids, 19-HETE, 20-HETE, and other forms of HETE. The metabolites of AA generated by the P450 enzymes have been found to play important roles in the regulation of vascular tone in renal, cerebral, coronary, and skeletal muscle arterioles and in pulmonary circulation. 1,2 More than 500 CYP genes have been identified; among them, CYP4F2, CYP4A11, and CYP4F3B are thought to be the major 1Section of Nephrology, Department of Internal
Medicine, Yale University School of Medicine, New Haven, Connecticut, USA Correspondence: Yiqiang Cai, Section of Nephrology, Department of Internal Medicine, Yale University School of Medicine, 300 Cedar Street, New Haven, CT 6510, USA. E-mail: [email protected]
genes involved in metabolizing AA to form 20-HETE.1,2 20-HETE is a potent constrictor of small arteries and arterioles; however, in the kidney, 20-HETE also regulates tubular sodium reabsorption in the proximal tubule, as well as in the thick ascending limb of Henle’s loop via inhibition of Na + -K + -ATPase activities or Na + -K + -2Cl– cotransport. Therefore, the influence of 20-HETE on blood pressure remains difficult to predict: it could play either a prohypertensive or an antihypertensive role, depending on its action as a vasoconstrictor or a sodium reabsorption inhibitor in renal tubules. 1,3 In addition, studies in human and animal models also suggest diverse effects of CYP gene function on blood pressure. In humans, functional polymorphism analysis demonstrated that diverse consequences resulted from genetic polymor phism: t he CYP4F2 GA / AA genotype was significantly associated with an increase in both 20-HETE excretion and systolic blood pressure, whereas the CYP4A11 CC/TC genotype was significantly associated with a reduction in 20-HETE excretion but 1253
com m enta r y
CYP4F2 ↑
20-HETE ↑
?
?
Elevated blood pressure
Figure 1 | Model of CPY4F2 gene function. Increased expression of CYP4F2 that caused increased production of 20-HETE was associated with elevated blood pressure. However, the mechanism(s) underlying the link between increased 20-HETE and hypertension, and whether other factors contributed to the elevated blood pressure, remain unknown.
was not associated with changes in blood pressure. 3 Furthermore, the CYP4F2 M433 variant caused decreased production of 20-HETE.4 On the other hand, the transfer of the CYP4A region of chromosome 5 from Lewis to Dahl salt-sensitive rats increased production of 20-HETE but attenuated the development of hypertension and renal disease. 5 These data combined indicate that further investigation is needed to better understand the overall effect of the functioning of CYP genes and 20HETE on blood pressure in vivo. Liu and colleagues6 (this issue) established a novel transgenic mouse model in which the human CYP4F2 gene was overexpressed under regulation of the mouse kidney androgen-regulated protein promoter. The authors showed overexpression of the CYP4F2 transgene in proximal tubules of the kidney but also in other organs. They found increased -hydroxylase activities and renal 20-HETE production in transgenic mice. Of importance, among three transgenic mouse lines, two were found to have significantly elevated 1254
systolic blood pressure that was positively ass o ciated with increas ed CYP4F2 expression and 20-HETE production. This study provides a novel gain-of-function mouse model showing for the first time that increased expression of the wild-type CYP4F2 gene results in increased production of 20-HETE and a positive association with elevated blood pressure in vivo . Considering the many potential effects that 20-HETE may have on blood pressure, the study by Liu et al. 6 suggests that increased production of 20-HETE has a prohypertensive role in vivo . In addition, previous studies showed that functional polymorphism of CYP4F2 could result in either increased or d e c re as e d 2 0 - H E T E pro du c t i on depending on the type of variation.3,4 The study by Liu et al. 6 suggests that the change in 20-HETE production, which links to a CYP4F2 polymorphism, may result from changes in the activity of the P450 4F2 enzyme. Currently, the mechanism or mechanisms that link CYP4F2 -derived increased 20-HETE production and elevated blood pressure remain unclear in this transgenic model (Figure 1). It was reported for the first time by Ward et al. that urinary 20-HETE is associated with endothelial dysfunction in humans.7 Moreover, an experimental study in rats further revealed that vascular P450 4A expression and 20-HETE synthesis contribute to endothelial dysfunction in androgen-induced hypertension. 8 Whether endothelial dysfunction resulted from the P450 4F2-derived increased 20-HETE production in the mouse model of Liu et al.6 remains undetermined. It is noteworthy that one transgenic mouse line in their study, F0-6, has slightly higher urinary 20-HETE than the transgenic line F0-56, which has elevated blood pressure but lacks significant elevated blood pressure in male mice. Whether this phenomenon results from genetic variation or reflects involvement of other factors such as endothelial dysfunction in the hypertensive phenotype remains to be determined. Another possibility is that increased CYP4F2 gene expression may also result in
increased production of 19-HETE, another metabolite of AA, which may act as a competitive antagonist of the inhibitory effects of 20-HETE on sodium reabsorption in the kidney. Further studies to address the above possibilities would help in understanding the mechanism(s) that links increased expression of CYP4F2 and 20-HETE production to elevated blood pressure in this transgenic model. Finally, transgene expression driven by the exogenous promoter might not faithfully recapitulate the native distribution profile of the target gene, which may result in functional consequences not seen in wild-type circumstances. In this regard, transgenic mouse overexpression of a bacterial artificial chromosome (BAC)CYP4F2 gene that carries the endogenous promoter may serve as a faithful model to establish the link between P450 4F2-derived 20-HETE production and changes in blood pressure in vivo. DISCLOSURE The author declared no competing interests.
REFERENCES 1.
2.
3.
4.
5.
6.
7.
8.
Roman RJ. P-450 metabolites of arachidonic acid in the control of cardiovascular function. Physiol Rev 2002; 82: 131–185. Miyata N, Roman RJ. Role of 20hydroxyeicosatetraenoic acid (20-HETE) in vascular system. J Smooth Muscle Res 2005; 41: 175–193. Ward NC, Tsai IJ, Barden A et al. A single nucleotide polymorphism in the CYP4F2 but not CYP4A11 gene is associated with increased 20-HETE excretion and blood pressure. Hypertension 2008; 51: 1393–1398. Stec DE, Roman RJ, Flasch A et al. Functional polymorphism in human CYP4F2 decreases 20HETE production. Physiol Genomics 2007; 30: 74–81. Williams JM, Sarkis A, Hoagland KM et al. Transfer of the CYP4A region of chromosome 5 from Lewis to Dahl S rats attenuates renal injury. Am J Physiol Renal Physiol 2008; 295: F1764–F1777. Liu X, Zhao Y, Wang L et al. Overexpression of cytochrome P450 4F2 in mice increases 20-hydroxyeicosatetraenoic acid production and arterial blood pressure. Kidney Int 2009; 75: 1288–1296. Ward NC, Rivera J, Hodgson J et al. Urinary 20hydroxyeicosatetraenoic acid is associated with endothelial dysfunction in humans. Circulation 2004; 110: 438–443. Singh H, Cheng J, Deng H et al. Vascular cytochrome P450 4A expression and 20-hydroxyeicosatetraenoic acid synthesis contribute to endothelial dysfunction in androgen-induced hypertension. Hypertension 2007; 50: 123–129. Kidney International (2009) 75