Conflicting roles of 20-HETE in hypertension and renal end organ damage.

20-HETE is a cytochrome P450-derived metabolite of arachidonic acid that has both pro- and anti-hypertensive actions that result from modulation of vascular and kidney function. In the vasculature, 20-HETE sensitizes vascular smooth muscle cells to constrictor stimuli and increases myogenic tone. By promoting smooth muscle cell migration and proliferation, as well as by acting on the vascular endothelium to cause endothelial dysfunction, angiotensin converting enzyme (ACE) expression, and inflammation, 20-HETE contributes to adverse vascular remodeling and increased blood pressure. A G protein-coupled receptor was recently identified as the effector for the vascular actions of 20-HETE. In addition, evidence suggests that 20-HETE contributes to hypertension via positive regulation of the renin-angiotensin-aldosterone system, as well as by causing renal fibrosis. On the other hand, 20-HETE exerts anti-hypertensive actions by inhibiting sodium reabsorption by the kidney in both the proximal tubule and thick ascending limb of Henle. This review discusses the pro- and anti-hypertensive roles of 20-HETE in the pathogenesis of hypertension-associated renal disease, the association of gene polymorphisms of cytochrome P450 enzymes with the development of hypertension and renal end organ damage in humans, and 20-HETE related pharmaceutical agents.

The isoforms of CYP enzymes that are responsible for the production of 20-HETE are different among species. CYP4A11, −4F2, and −4F3 are the isoforms that contribute to the production of 20-HETE in humans (Gainer et al., 2005;Hirani et al., 2008;Lasker et al., 2000;Powell et al., 1998). Among these isoforms, CYP4F2 is primarily responsible for the formation of 20-HETE in the kidney (Powell et al., 1998), and CYP4F3 is mainly expressed in polymorphonuclear leukocytes (PMNs) (Rosolowsky et al., 1996). CYP4A1, −4A2, −4A3, −4A8, −4F1, and −4F4 are the 20-HETE producing isoforms in rats (Kawashima et al., 1997;Kikuta et al., 1999;Nguyen et al., 1999;Williams et al., 2012;Xu et al., 2004). Among them, CYP4A1 exhibits the greatest catalytic activity (Xu et al., 2004). In mice, CYP4A10, −4A12a, −4A12b, and −4A14 are constitutively expressed, but only CYP4A12a is able to metabolize AA to 20-HETE (Dordea et al., 2016;Holla et al., 2001;Muller et al., 2007;Wu et al., 2013). However, unlike CYP4A10 and CYP4A14, CYP4A12 expression is weakly induced by fibrates and is also expressed differently in the tissues of male versus female mice (Holla et al., 2001). It should be noted that CYP4A genes are found in a single cluster on the same chromosome suggesting gene duplication. There are four genes of the 4A family in mice, rats, rabbits, and dogs. Man is the exception with only 2 isoforms and, unlike other species, has two related CYP4F genes on different chromosomes that produce 20-HETE. This could have occurred during a crossover event in evolution. Within the kidney, 20-HETE is expressed in pre-glomerular arterioles, glomeruli, proximal convoluted tubules, and pars recta. Of note, 20-HETE is the primary metabolite of AA in the thick ascending loop of Henle (TALH) in the nephron. activates MAPK. These signaling events ultimately lead to endothelial dysfunction as marked by deceased nitric oxide (NO) and increased reactive oxygen species due to uncoupling and/or loss of endothelial nitric oxide synthase (eNOS) (Fig. 1). 20-HETE also activates NF-κB signaling, which results in increased angiotensin-converting enzyme (ACE) expression that favors formation of hypertensive angiotensin II (Ang II). As discussed elsewhere (Fan and Roman, 2017), 20-HETE may also cause endothelial dysfunction and ACE expression via transactivation of the epidermal growth factor receptor (EGFR) (not shown).
In vascular smooth muscle cells (VSMCs), GPR75 activation is linked to protein kinase C (PKC)-mediated phosphorylation of the β subunit of the large conductance calcium-and voltage-activated potassium (BK) channels, which inhibits BK channel activity and causes vasoconstriction   (Fig. 1). GPR75 may explain the actions of 20-HETE in VSMCs and endothelial cells; however, this remains to be verified in proximal tubular and TALH cells, and to be determined whether GPR75 is the only 20-HETE receptor or whether others will be identified (Fan and Roman, 2017).
As discussed in our review and summarized in Table 1, 20-HETE has both pro-and antihypertensive actions. The former are attributed to its aforementioned actions on the endothelial cells and VSMC of both the renal and peripheral vasculature. The antihypertensive and extravascular actions of 20-HETE result from natriuretic and diuretic actions arising from inhibition of sodium reabsorption in both the proximal tubule (PT) and TALH. Confoundingly, the intra-renal, anti-hypertensive actions of 20-HETE are opposed by the renin-angiotensin-aldosterone-system (RAAS), which may be activated by 20-HETE.
The first implication of the relationship between 20-HETE and hypertension was reported in 1989 (Sacerdoti et al., 1989). The investigators found that selective depletion of renal cytochrome P450 and AA metabolites prevented elevated blood pressure in the Spontaneously Hypertensive Rat (SHR). Direct evidence was then provided in 1991 that SHR elevated in the kidney in SHR (Ishizuka et al., 2004;Kroetz et al., 1997;Omata et al., 1992a;Omata et al., 1992b;Schwartzman et al., 1996). Therefore, it seems that the hypertensive phenotype in the SHR is due to elevated renal 20-HETE formation and, thus, it would be expected that inhibition of renal production of 20-HETE would attenuate the degree of hypertension in this model. Indeed, induction of heme oxygenase (HO) reduced (Goodman et al., 2003) or blocked formation of 20-HETE and slowed development of hypertension in male Imig et al., 1993;Kroetz et al., 1997;Omata et al., 1992a;Schwartzman et al., 1996;Zhang et al., 2005) and post-menopausal female SHR (Yanes et al., 2011). Administration of dihydrotestosterone (DHT) in both male and female Sprague Dawley rats upregulated 20-HETE production in renal parenchymal and vascular tissues by elevating expression of CYP4A8 through the androgen receptor, and promoted development of hypertension (Singh et al., 2007;Singh and Schwartzman, 2008;Wu and Schwartzman, 2011).
The relationship of 20-HETE and hypertension was also investigated in hypertensive mouse models. Upregulation of CYP4A12 by exogenous DHT, or as is seen in nitric oxide (NO) receptor deficient sGCαl (−/−) mice, produced 20-HETE-dependent hypertension and vascular dysfunction (Dordea et al., 2016;Muller et al., 2007;Wu et al., 2013). CYP4A14 is highly expressed in female mice (Heng et al., 1997;Holla et al., 2001;Muller et al., 2007), but knockout of CYP4A14 (Fidelis et al., 2010;Holla et al., 2001;Muller et al., 2007) induced hypertension in male mice only. This was associated with an increase in plasma testosterone levels and renal CYP4A12 expression and 20-HETE formation, as well as reduced renal production of NO (Fidelis et al., 2010). These findings suggest that CYP4A14 may produce a metabolite that inhibits testosterone production. Hypertension in this model was reversed by castration (Holla et al., 2001) and the elevation in renal perfusion pressure to phenylephrine was blunted by an inhibitor of 20-HETE synthesis (Fidelis et al., 2010). More recent studies indicate that knock-in of human CYP4A11 (Savas et al., 2016) and CYP4F2 (Cai, 2009;Fava et al., 2009;Liu et al., 2009) in mice enhanced renal production of 20-HETE and promoted development of hypertension. Levels of 20-HETE were also elevated in various tissues including kidneys and endothelial cells in endothelial-specific human CYP4F2 transgenic mice (Cheng et al., 2014); however, blood pressure was not altered in this model. These studies indicate that increased formation of 20-HETE is associated with elevations in blood pressure in male, but not female mice, since it is linked to elevations in testosterone-induced CYP4A12 expression. The relationship between these findings and the influence of 20-HETE on the development of hypertension in man remain to be determined.
3. Impact of 20-HETE on hypertensive vascular remodeling and nephropathy 20-HETE plays a pro-fibrotic role in hypertensive nephropathy. In streptozotocin (STZ) treated diabetic CYP4A14 KO mice, the increased renal 20-HETE production (due to increased plasma testosterone levels and consequent induction of CYP4A12 gene expression) was associated with hypertension (Gangadhariah et al., 2015;Holla et al., 2001) and exacerbated renal injury. Increased urinary protein excretion, expansion of mesangial and glomerular basement membranes, and deposition of glomerular matrix were observed (Gangadhariah et al., 2015;Holla et al., 2001). These results are consistent with previous studies that enhanced CYP4A/20-HETE levels accompanied elevated reactive oxygen species production in cultured mouse podocytes (Eid et al., 2009) and rat proximal tubular epithelial cells (Eid et al., 2013). Increased expression of 20-HETE in STZ-treated mice and rats was also associated with increased reactive oxygen species generation, NADPH oxidase activity (Eid et al., 2009), transforming growth factor-β1 (TGF-β1) and fibronectin expression, as well as glomerular matrix formation, podocyte apoptosis, and urinary protein excretion (Eid et al., 2009;Elmarakby et al., 2013).
Vascular remodeling is one of the key pathophysiological processes in hypertension and is related to an increase in the media-to-lumen ratio of small arteries and arterioles, leading to vascular hyperactivity to constrictor stimuli and enhanced peripheral resistance (Renna et al., 2013). The renal expression of 20-HETE is increased in SHR, and 20-HETE is involved in the augmented renal vascular reactivity to Ang II, which results in profound vascular remodeling . 20-HETE also contributes to vascular hypertrophy in a CYP4A12 transgenic mouse independent of the increase in mean arterial pressure (Wu et al., 2013). These studies demonstrate that 20-HETE plays a role in vascular remodeling, a process that involves activation of multiple vascular components such as endothelium and VSMCs, and deposition of extracellular matrix (ECM) and basement membrane (McGrath et al., 2005).
Besides promoting proliferation of VSMCs Orozco et al., 2013), which has been implicated in restenosis, 20-HETE also stimulates mitogenesis of endothelial (Chen et al., 2012;Cheng et al., 2014;Guo et al., 2007) and renal epithelial cells . 20-HETE-induced endothelial cell proliferation may contribute to atherosclerotic neovascularization/angiogenesis and related plaque instability and rupture (Chen et al., 2012;Moreno et al., 2006;Sun, 2014), events that are associated with and exacerbated by hypertension (Picariello et al., 2011). Renal epithelial cell proliferation has significant implications for polycystic kidney disease (PKD) , which commonly is associated with hypertension, although the mechanism is unclear. 20-HETE is stimulated by pro-angiogenic factors such as hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) to promote cell migration and proliferation (Chen et al., 2014;Muthalif et al., 1998;Parmentier et al., 2001a;Stec et al., 2007a). Moreover, 20-HETE induces VEGF expression that drives endothelial cell proliferation in a signaling cascade involving apocynin-insensitive reactive oxygen species production and extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) activation (Chen et al., 2014;Guo et al., 2007). In kidney epithelial cells, 20-HETE was found to activate the mitogenic Raf/MEK/ERK and protein kinase B (PKB/Akt) signaling pathways via c-Src-mediated transactivation of EGFR . Whether 20-HETE also acts on renal epithelial cells through the same GPR75 receptor as on endothelial and VSMCs remains to be determined (Fan and Roman, 2017;Garcia et al., 2017). Overall, these studies suggest that 20-HETE plays a role in vascular or kidney remodeling, which might be associated with its effect to promote angiogenesis and endothelial or renal epithelial cell proliferation.
20-HETE has also been known to play a role in promoting vascular inflammation. Arteries that were treated with a biosynthesis inhibitor of 20-HETE, HET0016 resulted in attenuation of reactive oxygen species and vascular nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation, and reduction of vascular inflammation, which was associated with decreases in pro-inflammatory cytokine expression, such as tumor necrosis factor-alpha (TNFα), interleukin-1 beta (IL-1β), and IL-6 (Toth et al., 2013). 20-HETE has also been found to induce expression of multiple adhesion molecules such as monocyte chemotactic protein 1 (MCP-1), intercellular adhesion molecule 1 (ICAM-1), and vascular cell adhesion protein 1 (VCAM-1) in the vasculature (Hoopes et al., 2015). The adhesion molecules increase vascular inflammation by recruiting monocytes and macrophages to the vascular wall.

Interplay between 20-HETE and the renin-angiotensin-aldosterone system (RAAS) in hypertension and hypertensive nephropathy
The renin-angiotensin-aldosterone system, which acts either in a systemic endocrine or in a local paracrine/autocrine fashion, plays an important role in cardiovascular homeostasis (Harrison-Bernard, 2009). Ang II is the central bioactive component of the RAAS and exerts a crucial role in regulating vascular myogenic tone in normal physiology, as well as in the pathogenesis of hypertension and other cardiovascular disorders (Mehta and Griendling, 2007;Paul et al., 2006). Reduced arterial blood pressure, a decrease in sodium load, or activation of the sympathetic nervous system (SNS) all stimulate renin secretion (Paul et al., 2006). Renin cleaves angiotensinogen to produce Ang I, which is further converted to Ang II by ACE . Tissue-specific renin-or ACE-independent routes for Ang II formation have also been identified (Forrester et al., 2018). In addition, evidence has suggested that the kidney expresses all necessary components for Ang II formation and thus possesses a local renin-angiotensin-system, although recent reports question the intra-renal origins of angiotensinogen and other system components .
Emerging evidence suggests a complex interplay between 20-HETE and the RAAS. A positive feedback between 20-HETE and Ang II exists and contributes to vasoconstriction and hypertension (Alonso-Galicia et al., 2002;Chu et al., 2000;Croft et al., 2000;Fan et al., 2013b;Joly et al., 2006;Park et al., 2001). Ang II increases renal production of 20-HETE (Alonso-Galicia et al., 2002), while the RAAS is suppressed in a salt-sensitive hypertensive rat with decreased expression of glomerular CYP4A1 (Ito and Roman, 1999). Chronic deoxycorticosterone acetate (DOCA)-salt treatment suppresses the systemic renin-angiotensin system, and 20-HETE expression was reduced in a DOCA-salt hypertensive mouse model (Honeck et al., 2000); however, 20-HETE levels were elevated in the DOCAsalt hypertensive rat (Oyekan et al., 1999), perhaps implicating a direct role for the mineralocorticoid receptor in this model.
Recent studies demonstrated that 20-HETE activates the RAAS in part by inducing vascular expression of ACE downstream of NF-κB activation (Cheng et al., 2012;Garcia et al., 2016;Sodhi et al., 2010); however, 20-HETE-mediated microvascular remodeling in hypertension did not fully rely on ACE activity in the vascular endothelium (Cheng et al., 2012;. Moreover, increased 20-HETE may not necessarily be associated with enhanced RAAS activity. For instance, fenofibrate treatment induced intrarenal 20-HETE production, thereby attenuating hypertension in an Ang II-dependent mouse model via enhanced sodium excretion (see below, Role of 20-HETE in preventing hypertension and hypertensive nephropathy) (Vera et al., 2005). In contrast, fenofibrate increased renal production of 20-HETE and plasma renin activity in both Stroke-Prone Spontaneously Hypertensive Rats (SHRSP) and salt-sensitive hypertensive Dahl S rats (Shatara et al., 2000). In a humanderived 20-HETE-producing CYP4A11 transgenic mouse, 20-HETE enhanced the production of renal angiotensinogen and activation of Ang II type 1 (AT1) receptor and this enhancement paralleled an increase in plasma potassium level and in activities of the sodium chloride co-transporter (NCC) and serum/glucocorticoid regulated kinase 1 (SGK1), even though plasma aldosterone, Ang II, and renin activities remained unchanged (Savas et al., 2016). This investigation suggests that 20-HETE may contribute to hypertension and its complications via upregulation of sodium transport in the distal nephron secondary to increased activity of RAAS.
Hypertension in the SHR is dependent on both the RAAS and 20-HETE and is associated with elevated sympathetic tone. Little is known as to whether 20-HETE interacts with Ang II to increase sympathetic activity or potentiates the effects of norepinephrine at the level of smooth muscle. More studies are necessary to elucidate whether the link between 20-HETE and RAAS is mediated solely via changes in vascular reactivity, sodium retention activation of the SNS, or via combinational effects.

Hypertensive actions of 20-HETE summarized
20-HETE promotes hypertension by several means involving both the peripheral vasculature and kidney. It serves as an autocrine second messenger and enhances the vascular response to constrictor stimuli in peripheral VSMCs, as well as renal afferent arteries. It also promotes endothelial dysfunction, and induces vascular inflammation, and RAAS activation. Furthermore, 20-HETE promotes renal oxidative stress and fibrosis, directly or via apoptosis of kidney cells. These factors, in our opinion, mainly account for the role of 20-HETE in promoting hypertension and contributing to hypertension associated renal end organ damage.

Role of 20-HETE in preventing hypertension and hypertensive nephropathy
On the other hand, 20-HETE prevents hypertension by inhibiting sodium reabsorption and promoting natriuresis (Fig. 2). It inhibits Na + -K + -ATPase activity and internalizes sodiumhydrogen exchanger 3 (NHE3) in the PT, thereby diminishing sodium transport in renal tubules (Capdevila et al., 2003;Fan et al., 2016;Fan et al., 2015b;Roman, 2002). In the TALH, 20-HETE inhibits Na + reabsorption and induces natriuresis by several means: 20-HETE a) inhibits the basolateral Na + /K + -ATPase and luminal Na + -K + −2Cl − cotransporter; and b) inhibits both the luminal 70 pS K + channel responsible for K + back-leak that sustains cotransporter activity and the basolateral 50 pS K + channel that affects cotransporter activity by controlling the driving force for Cl − cellular exit Fan et al., 2015b;Gu and Wang, 2002;Roman, 2002;Yu et al., 2007) Induction of renal formation of 20-HETE with fibrates attenuates, rather than promotes, high blood pressure in SHRSP (Shatara et al., 2000) or SHR (Hou et al., 2010). The divergent results can be understood by the observation that fenofibrate increases renal 20-HETE and natriuresis, but does not alter vascular 20-HETE, because blood vessels do not express peroxisome proliferator-activated receptor alpha (PPAR-α) (Vera et al., 2005). This finding suggests that the 20-HETE produced in renal tubules may contribute to the blood pressurelowering effects of fibrates treatment in Ang II-dependent hypertension without affecting or overweighting its effects on vascular tone. This viewpoint is supported by more recent studies in the Dahl S rats.
The Dahl S rat is a low renin, salt-sensitive model of hypertension due to enhanced reabsorption of sodium in the PT and TALH. In the Dahl S rat, reduced levels of CYP4A and 20-HETE are associated with rapid development of hypertension with salt diet, impaired pressure natriuresis relationship, and abnormal sodium transport in the kidney (Williams et al., 2008;Williams et al., 2007b). These rats also have impaired renal microvascular function (Fan et al., 2013a;Ge et al., 2014). These findings are similar to another study in SHR, whereby the induction of 20-HETE with fibrates attenuated hypertension and reduced proteinuria (Shatara et al., 2000). Transfer of chromosome 5 which contains 4 isoforms of CYP4A enzymes from normotensive Lewis or Brown Norway (BN) strains or transfer of a single BN CYP4A1 gene to the Dahl S rat prevented development of hypertension, improved natriuresis, and rescued the impaired myogenic response of both renal and cerebral arterioles (Fan et al., 2013a;Fan et al., 2014;Ge et al., 2014;Murphy et al., 2013;Williams et al., 2012;Williams et al., 2008).
Dahl S rats exhibit a deficiency in the formation of 20-HETE (Fan et al., 2015a;Williams et al., 2012;Williams et al., 2008), an elevation in glomerular capillary pressure, and an increase in permeability of the glomerulus to albumin, which are associated with enhanced renal TGF-β1 expression and development of hypertension-induced chronic kidney disease (Fan et al., 2015a;Williams et al., 2012;Williams et al., 2008). These rats also have impaired renal myogenic and TGF responses, increased renal interstitial pressure in response to elevation of renal perfusion pressure, and a reset of pressure-natriuresis (Fan et al., 2013a;Ge et al., 2014;Ren et al., 2014). The renal protective effect of 20-HETE was confirmed in transgenic Dahl S rats in which the CYP4A gene(s) was knocked in or overexpressed Murphy et al., 2013;Williams et al., 2012;Williams et al., 2008). These rats exhibited diminished albumin permeability, rescued glomerular filtration rate (GFR), and attenuated glomerular capillary leakage (Dahly-Vernon et al., 2005;Williams et al., 2007b). More evidence was recently provided that 20-HETE, a physiological substrate of ADH in podocytes, protected the glomerular permeability barrier in ethanol treated mice in which CYP4A12a was upregulated by blocking cytoskeletal derangement and production of superoxide (McCarthy et al., 2015).
The available evidence suggests that elevated 20-HETE induces hypertension, but prevents renal injury due to elevation of renal vascular tone in models associated with involvement of RAAS. Results with a 20-HETE inhibitor in Lyon hypertensive rats further support this conclusion (Lantelme et al., 1997;Messer-Letienne et al., 1999;Williams et al., 2007a). Deficiencies in 20-HETE in the kidney increase tubular sodium reabsorption and promote salt-sensitive hypertension and renal injury due to decreased renal vascular reactivity.

Human genetic studies
In humans, CYP4F2 is the most potent isoform, followed by CYP 4A11, among the predominant 20-HETE producing enzymes: CYP4A11, −4A22, −4F2, and −4F3 (Gainer et al., 2005;Hirani et al., 2008;Lasker et al., 2000;Powell et al., 1998). A number of single nucleotide polymorphisms (SNPs) in the CYP4F2 (V433M, G421C, GA/AA) and CYP4A11 (T8590C) genes have been reported to play a role in the development of hypertension in several cohorts Laffer et al., 2008;Liu et al., 2008;Liu et al., 2006;Mayer et al., 2005;Ward et al., 2008;Williams et al., 2011). Among these SNPs, the V433M variant (Stec et al., 2007b) in CYP4F2 and the T8590C variant (Gainer et al., 2005) in CYP4A11 decrease the activities of these enzymes, and the later SNP is also associated with the pathogenesis of salt-sensitive hypertension (Williams et al., 2007b;Yanes et al., 2011). Other reports showed that the renal excretion of 20-HETE-glucuronide is elevated in hypertensive patients with CYP4F2 SNPs (Liu et al., 2008;Ward et al., 2008). These authors suggested that 20-HETE might promote hypertension by enhancing renal vasoconstriction, but this hypothesis remains to be validated because renal blood flow (RBF) or GFR was not measured in these hypertensive patients. Moreover, recent studies have indicated that urinary glucuronide conjugate-20-HETE is not of renal origin, since the amount of the conjugated form of 20-HETE is higher in the plasma than in urine when the fractional excretion is <1% (Dreisbach et al., 2014).
Overall, these studies indicate that 20-HETE plays an important role in the development of hypertension in humans. However, more studies are needed to determine to what extent changes in 20-HETE production contribute to the antihypertensive effects of diuretics, ACE inhibitors, AT1 receptor antagonists, and other antihypertensive agents.

The development of 20-HETE related pharmaceutical agents
Along the way in studying the role of 20-HETE in various pathological processes, a variety of 20-HETE-related pharmaceutical agents have been synthesized (Williams et al., 2010;Yu et al., 2004) (Fig. 3). These include CYP inhibitors and inducers, and 20-HETE agonists and antagonists. In the early period, several specific inhibitors of CYP4A enzymes were synthesized and used for evaluating the role of CYP metabolites of AA, such as 1aminobenzotriazole (ABT) and 17-octadecynoic acid (17-ODYA) (Knickle and Bend, 1992;Mathews et al., 1985;Zou et al., 1994). However, they were not satisfactory because they are not specific and could also block the formation of EETs (Knickle and Bend, 1992;Maier et al., 2000;Mathews et al., 1985;Zou et al., 1994), a group of AA metabolites with effects on vascular function generally opposite to 20-HETE. The second generation of inhibitors to specifically block formation of 20- HETE,12,, were synthesized by Dr. Falck (Alonso-Galicia et al., 1997;Wang et al., 1998). These compounds proved to completely inhibit formation of 20-HETE at a concentration of 10 μM, whereas the activity of EETs was only reduced by 10-20% under the same condition (Alonso-Galicia et al., 1997). The main limitation of these agents is their fatty acid property with a rather high albumin-binding rate in the plasma, which restricts distribution of these compounds to targeted tissues.
A new inhibitor of CYP4A enzymes, N-hydroxy-N'-(4-n-butyl-2-methylphenyl) formamidine (HET-0016) was created (Miyata et al., 2001). This compound could inhibit formation of 20-HETE in a potent and selective way for its IC 50 is only 8.9 nM and it has no effect on other enzymes that are responsible for AA metabolism such as COX, epoxygenase, LOX, or other CYP isoforms that are not involved in producing 20-HETE (Miyata et al., 2001). Later, a more potent and selective HET-0016 analog, TS011 was developed (Williams et al., 2010). In general, HET-0016 is commercially available and is the most widely used inhibitor of 20-HETE synthesis.
Very recently, a novel water-soluble 20- HETE antagonist,2,5,8,11,14,, 15(Z)-dienoate (20-SOLA) was synthesized. Administration of 20-SOLA was found to reduce blood pressure as a result of increased natriuresis in hypertensive CYP4A14 KO mice . This model of androgen-driven hypertension is associated with both 20-HETE-induced vasoconstriction and renal hypoperfusion, as well as excessive sodium and volume reabsorption due to Ang II-induced upregulation of NHE3 in the proximal tubule and NCC in the distal convoluted tubule. Increased renal Ang II is likely attributed to 20-HETE-driven vascular ACE or renal angiotensinogen expression. Thus, the anti-hypertensive actions of the 20-SOLA in this hypertensive model may have resulted from increased glomerular filtration and attenuation of the RAAS. Finally, Dr. Eric F. Johnson reported a more soluble 20-HETE antagonist than 6, 15-20-HEDE, sodium (S)-2-((6Z, 15Z)-20-hydroxyicosa-6, 15-dienamido)-succinate (AAA), which contributed to the reduced blood pressure in human CYP 4A11 transgenic mice (Savas et al., 2016). These compounds appear to be the most likely candidates for drug development for treatment of myocardial infarction, stroke, chronic kidney disease, neovascularization and other 20-HETE-associated cardiovascular complications.