Corticosterone metabolism and effects on angiotensin II receptors in vascular smooth muscle

Intrarenal Renin Angiotensin System Imbalance During Postnatal Life Is Associated With Increased Microvascular Density in the Mature Kidney

Environmental stress during early life is an important factor that affects the postnatal renal development. We have previously shown that male rats exposed to maternal separation (MatSep), a model of early life stress, are normotensive but display a sex-specific reduced renal function and exacerbated angiotensin II (AngII)-mediated vascular responses as adults. Since optimal AngII levels during postnatal life are required for normal maturation of the kidney, this study was designed to investigate both short- and long-term effect of MatSep on (1) the renal vascular architecture and function, (2) the intrarenal renin-angiotensin system (RAS) components status, and (3) the genome-wide expression of genes in isolated renal vasculature. Renal tissue and plasma were collected from male rats at different postnatal days (P) for intrarenal RAS components mRNA and protein expression measurements at P2, 6, 10, 14, 21, and 90 and microCT analysis at P21 and 90. Although with similar body weight and renal mass trajectories from P2 to P90, MatSep rats displayed decreased renal filtration capacity at P90, while increased microvascular density at both P21 and P90 (p < 0.05). MatSep increased renal expression of renin, and angiotensin type 1 (AT1) and type 2 (AT2) receptors (p < 0.05), but reduced ACE2 mRNA expression and activity from P2-14 compared to controls. However, intrarenal levels of AngII peptide were reduced (p < 0.05) possible due to the increased degradation to AngIII by aminopeptidase A. In isolated renal vasculature from neonates, Enriched Biological Pathways functional clusters (EBPfc) from genes changed by MatSep reported to modulate extracellular structure organization, inflammation, and pro-angiogenic transcription factors. Our data suggest that male neonates exposed to MatSep could display permanent changes in the renal microvascular architecture in response to intrarenal RAS imbalance in the context of the atypical upregulation of angiogenic factors.

Dexamethasone in the era of COVID-19: friend or foe? An essay on the effects of dexamethasone and the potential risks of its inadvertent use in patients with diabetes

BACKGROUND

The disclosure in the media of a benefit with the use of dexamethasone in patients with COVID-19 infection sets precedents for self-medication and inappropriate use of corticosteroids.

METHODS

This is a critical interpretive synthesis of the data available in the literature on the effects of the use of corticosteroids and the impact that their indiscriminate use may have on patients with diabetes. Reviews and observational and experimental studies published until June 18, 2020 were selected.

RESULTS

Corticosteroids are substances derived from cholesterol metabolism that interfere with multiple aspects of glucose homeostasis. Interactions between corticoid receptors and target genes seem to be among the mechanisms responsible for the critical functions of glucocorticoids for survival and anti-inflammatory effects observed with these medications. Corticosteroids increase hepatic gluconeogenesis, reduce peripheral use of glucose and increase insulin levels. Previous studies have shown that glucocorticoids have a pro-adipogenic function, increasing deposition of abdominal fat, and lead to glucose intolerance and hypertriglyceridemia. In addition, these drugs play a role in controlling liver metabolism and can lead to the development of hepatic steatosis. Glucocorticoids reduce the recruitment of osteoblasts and increase the number of osteoclasts, which results in increased bone resorption and greater bone fragility. Moreover, these medications cause water and sodium retention and increase the response to circulating vasoconstrictors, which results in increased blood pressure levels. Chronic or high-dose use of corticosteroids can, by itself, lead to the onset of diabetes. For those who were already diagnosed with diabetes, studies show that chronic use of corticosteroids leads to a 94% higher risk of hospitalization due to diabetes complications. In addition to the direct effects on glycemic control, the effects on arterial pressure control, lipids and bone metabolism also have a potential for severe consequences in patients with diabetes.

CONCLUSION

Fear and uncertainty toward a potentially serious infection may lead people to self-medication and the inappropriate and abusive use of corticosteroids. More than ever, it is necessary for health professionals to be alert and able to predict damages related to the use of these drugs, which is the first step to minimize the potential damages to come.

An alternative explanation of hypertension associated with 17α-hydroxylase deficiency syndrome

The syndrome of 17α-hydroxylase deficiency is due to the inability to synthesize cortisol and is associated with enhanced secretion of both corticosterone and 11-deoxy-corticosterone (DOC). In humans, corticosterone and its 5α-Ring A-reduced metabolites are excreted via the bile into the intestine and transformed by anaerobic bacteria to 21-dehydroxylated products: 11β-OH-progesterone or 11β-OH-(allo)-5α-preganolones (potent inhibitors of 11β-HSD2 and 11β-HSD1 dehydrogenase). Neomycin blocks the formation of these steroid metabolites and can blunt the hypertension in rats induced by either ACTH or corticosterone. 3α,5α-Tetrahydro-corticosterone, 11β-hydroxy-progesterone, and 3α,5α-tetrahydro-11β-hydroxy-progesterone strongly inhibit 11β-HSD2 and 11β-HSD1 dehydrogenase activity; all these compounds are hypertensinogenic when infused in adrenally intact rats. Urine obtained from a patient with 17α-hydroxylase deficiency demonstrated markedly elevated levels of endogenous glycyrrhetinic acid-like factors (GALFs) that inhibit 11β-HSD2 and 11β-HSD1 dehydrogenase activity (>300 times greater, and >400 times greater, respectively, than those in normotensive controls). Thus, in addition to DOC, corticosterone and its 5α-pathway products as well as the 11-oxygenated progesterone derivatives may play a previously unrecognized role in the increased Na(+) retention and BP associated with patients with 17α-hydroxylase deficiency.

Endogenous inhibitors (GALFs) of 11beta-hydroxysteroid dehydrogenase isoforms 1 and 2: derivatives of adrenally produced corticosterone and cortisol

Two isoforms of 11beta-HSD exist; 11beta-HSD1 is bi-directional (the reductase usually being predominant) and 11beta-HSD2 functions as a dehydrogenase, conferring kidney mineralocorticoid specificity. We have previously described endogenous substances in human urine, "glycyrrhetinic acid-like factors (GALFs)", which like licorice, inhibit the bi-directional 11beta-HSD1 enzyme as well as the dehydrogenase reaction of 11beta-HSD2. Many of the more potent GALFs are derived from two major families of adrenal steroids, corticosterone and cortisol. For example, 3alpha5alpha-tetrahydro-corticosterone, its derivative, 3alpha5alpha-tetrahydro-11beta-hydroxy-progesterone (produced by 21-deoxygenation of corticosterone in intestinal flora); 3alpha5alpha-tetrahydro-11beta-hydroxy-testosterone (produced by side chain cleavage of cortisol); are potent inhibitors of 11beta-HSD1 and 11beta-HSD2-dehydrogenase, with IC50's in range 0.26-3.0 microM, whereas their 11-keto-3alpha5alpha-tetrahydro-derivatives inhibit 11beta-HSD1 reductase, with IC50's in range 0.7-0.8 microM (their 3alpha5beta-derivatives being completely inactive). Inhibitors of 11beta-HSD2 increase local cortisol levels, permitting it to act as a mineralocorticoid in kidney. Inhibitors of 11beta-HSD1 dehydrogenase/11beta-HSD1 reductase serve to adjust the set point of local deactivation/reactivation of cortisol in vascular and other glucocorticoid target tissues, including adipose, vascular, adrenal tissue, and the eye. These adrenally derived 11-oxygenated C21- and C19 -steroidal substances may serve as 11beta-HSD1- or 11beta-HSD2-GALFs. We conclude that adrenally derived products are likely regulators of local cortisol bioactivity in humans.

Mechanisms of vascular angiotensin II surface receptor regulation by epidermal growth factor

We investigated mechanisms by which epidermal growth factor (EGF) reduces angiotensin II (AngII) surface receptor density and stimulated actions in vascular smooth muscle cells (VSMC). EGF downregulated specific AngII radioligand binding in intact cultured rat aortic smooth muscle cells but not in cell membranes and also inhibited AngII-stimulated contractions of aortic segments. Inhibitors of cAMP-dependent kinases, PI-3 kinase, MAP kinase, cyclooxygenase, and calmodulin did not prevent EGF-mediated downregulation of AngII receptor binding, whereas the EGF receptor kinase inhibitor AG1478 did. Total cell AngII AT1a receptor protein content of EGF-treated and untreated cells, measured by immunoblotting, did not differ. Actinomycin D or cytochalasin D, which interacts with the cytoskeleton, but not the protein synthesis inhibitor cycloheximide, prevented EGF from downregulating AngII receptor binding. Consistently, EGF inhibited AngII-stimulated formation of inositol phosphates in the presence of cycloheximide but not in the presence of actinomycin D or cytochalasin D. In conclusion, EGF needs an intact signal transduction pathway to downregulate AngII surface receptor binding, possibly by altering cellular location of the receptors.

Effect of chenodeoxycholic acid on 11beta-hydroxysteroid dehydrogenase in various target tissues

Glucocorticoids are metabolized by isoforms of the enzyme 11beta-hydroxysteroid dehydrogenase (11beta-HSD). There is some controversy concerning the bile acid, chenodeoxycholic acid (CDCA), as a potential endogenously produced inhibitor of 11beta-HSD. The present experiments were designed to determine the relative specificity of CDCA for both isoforms of 11beta-HSD and to assess the biological relevance of inhibition in vascular tissue. IC(50) values (concentrations which inhibit 50% of the enzyme reaction) were calculated using rat liver microsomes as a source of 11beta-HSD1 dehydrogenase, Leydig cells for 11beta-HSD1 dehydrogenase and reductase, aorta for 11beta-HSD1 dehydrogenase and reductase, and sheep kidney for 11beta-HSD2 dehydrogenase. In each case, CDCA functioned as a potent inhibitor of 11beta-HSD1 dehydrogenase with IC(50) values of ranging from 0.2 to 7 micromol/L in contrast to 37 to 200 micromol/L for 11beta-HSD1 reductase. CDCA exhibited relatively weak inhibitory activity against 11beta-HSD2 from sheep kidney with an IC(50) of 70 micromol/L. The effect of CDCA on vascular contraction was studied in aortic rings isolated from Spague-Dawley rats incubated in medium containing corticosterone 10 nmol/L +/- CDCA (1 micromol/L) for 24 hours. Rings were stimulated with graded concentrations of phenylephrine (PE) (10 nmol/L, 100 nmol/L, and 1 micromol/L). Rings exposed to corticosterone and CDCA consistently demonstrated a greater contractile response at lower doses of PE (63% at PE 10 nmol/L, P <.001; 20% at PE 100 nmol/L, P <.025; and 10% at PE 1 micromol/L, not significant [NS]) compared to control preparations incubated with cortiosterone alone. These studies demonstrate (1) that CDCA preferentially affects 11beta-HSD1 dehydrogenase; (2) CDCA does inhibit 11beta-HSD2 dehydrogenase and 11beta-HSD1 reductase but only at high(er) concentrations exceeding 70 micromol/L and 37 micromol/L, respectively; and (3) inhibition of 11beta-HSD1 dehydrogenase in aortic rings by CDCA (1 micromol/L) enhances the contractile response of corticosterone plus PE.

The functional roles of 11 beta-HSD1: vascular tissue, testis and brain

Glucocorticoid hormones bind both glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) exerting a broad spectrum of actions in various tissues. The concentrations of glucocorticoid hormones in the target cells are regulated by 11 beta-hydroxysteroid dehydrogenases, type 1 (11 beta-HSD1) and type 2 (11 beta-HSD2). 11 beta-HSD2 is a unidirectional dehydrogenase, which inactivates biologically active glucocorticoid into inert metabolite, while 11 beta-HSD1 is a bi-directional oxidoreductase, which either inactivates biologically active glucocorticoid or activates inert metabolite into active forms. GRs and MRs are present in various tissues and mediate a broad spectrum of physiological actions. The co-existence of 11 beta-HSD1 with these two types of receptors plays an important role in regulation of glucocorticoid actions. This review examines the roles of 11 beta-HSD1 in vascular tissues, testis, brain and other tissues such as placental, retinal and adipose tissues.

11 beta-Hydroxysteroid dehydrogenase antisense affects vascular contractile response and glucocorticoid metabolism

Glucocorticoids (GC's) are metabolized in vascular tissue by two isoforms of 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD). 11 beta-HSD2 is unidirectional and metabolizes GC's to their respective inactive 11-dehydro derivatives. 11 beta-HSD1 is bi-directional, also possessing reductase activity and thus the ability to regenerate active GC from the 11-dehydro derivatives. In vascular tissue, GC's amplify the pressor responses to catecholamines and angiotensin II and may down-regulate certain depressor systems such as nitric oxide and prostaglandins. We hypothesize that both 11 beta-HSD2 and 11 beta-HSD1 regulate GC levels in vascular tissue and are part of additional mechanisms that control vascular tone. We examined the effects of specific antisense oligomers to 11 beta-HSD2 and 11 beta-HSD1 on GC metabolism and contractile response to phenylephrine (PE) in rat aortic rings. In aortic rings incubated (24 h) with corticosterone (B) (10 nmol/l) and 11 beta-HSD2 antisense (3 micromol/l), the contractile response to graded concentrations of PE (PE: 10 nmol/l - 1 micromol/l) were significantly (P < 0.05) increased compared to rings incubated with B and 11 beta-HSD2 nonsense. 11 beta-HSD1 antisense oligomers also enhanced the ability of B to amplify the contractile response to PE. In addition, 11 beta-HSD2 and 11 beta-HSD1 antisense also decreased the metabolism of B to 11-dehydro-B. 11-Dehydro-B (100 nmol/l) also amplified the contractile response to PE in aortic rings (P < 0.01), most likely due to the generation of active corticosterone by 11 beta-HSD1-reductase; this effect was significantly attenuated by 11 beta-HSD1 antisense. 11 beta-HSD1 antisense also caused a marked decrease in the metabolism of 11-dehydro-B back to B by 11 beta-HSD1-reductase. These findings underscore the importance of 11 beta-HSD2 and 11 beta-HSD1 in regulating local concentrations of GC's in vascular tissue. They also indicate that decreased 11 beta-HSD2 activity may be a possible mechanism in hypertension and that 11 beta-HSD1-reductase may be a possible target for anti-hypertensive therapy.

Glycyrrhetinic acid decreases plasma potassium concentrations in patients with anuria

ABSTRACT. Licorice-associated hypertension is thought to be due to increased renal sodium retention. The active compound of licorice, glycyrrhetinic acid (GA), inhibits renal 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) and by that mechanism increases access of cortisol to the mineralocorticoid receptor that causes renal sodium retention and potassium loss. In addition, a direct vascular effect of 11beta-HSD activity has recently been incriminated to promote hypertension, a contention based on in vitro observations. This investigation was designed to establish whether this extrarenal effect of 11beta-HSD is relevant for BP regulation and potassium concentrations in plasma. In a prospective, double-blind, cross-over study, seven patients with anuria on chronic hemodialysis were randomly assigned after a baseline period of 2 wk to placebo or GA (1 g/d) for 2 wk, separated by a washout phase of 3 wk. The ratio of plasma cortisol/cortisone, determined by gas chromatography-mass spectrometry, increased in all patients after GA intake (F = 9.705; P < 0.004), which indicates inhibition of 11beta-HSD. Twenty-four-hour BP values did not change throughout the study. The increase of the plasma cortisol/cortisone ratio was paralleled by a decline in the plasma potassium concentration in every patient. The mean +/- SD plasma potassium concentration decreased from 5.5 +/- 0.6 mM/L at baseline to 4.9 +/- 0.7 and 4.5 +/- 0.8 mM/L after 1 and 2 wk on GA, respectively (F = 9.934, P < 0.003). Extrarenal 11beta-HSD activity influences serum potassium concentrations but does not regulate BP independently of renal sodium retention.

Insights Into Glucocorticoid-Associated Hypertension

The association between excess glucocorticoids and hypertension has been much discussed but poorly understood. From both clinical observations and laboratory studies, it is clear that glucocorticoids exert their effects at many different sites responsible for blood pressure regulation. Isoforms of the enzyme 11ss-hydroxysteroid dehydrogenase (11ss-HSD), located in steroid-responsive tissues, metabolize endogenously produced glucocorticoids. These enzymes limit steroid access to mineralocorticoid and/or glucocorticoid receptors. In the kidney, synthetic and endogenous glucocorticoids are capable of enhancing transepithelial sodium transport in the presence of 11ss-HSD inhibition. Proximal tubule reabsorption of sodium can be indirectly augmented after chronic exposure to glucocorticoids. In this segment, steroids have a permissive effect, increasing the expression of both Na(+), K(+) adenosine triphosphatase along the basolateral membrane and Na(+)-H(+) exchanger along the apical membrane of epithelial cells. Although glucocorticoids themselves produce no increase in sodium reabsorption in this segment, angiotensin II-stimulated sodium transport is significantly greater in proximal tubular cells pretreated with glucocorticoids. The increased transport in distal renal segments is more direct and stems in part from glucocorticoid cross-over binding to mineralocorticoid receptors. In vascular tissue, synthetic and endogenous glucocorticoids, after inhibition of the dehydrogenase reaction, magnify the response to circulating vasoconstrictors. The effects of glucocorticoids in vascular tissue is indirect, upregulating the expression of receptors to many vasoconstrictors and downregulating the effects of potential vasodilators. Thus, glucocorticoids have the potential to alter both circulating volume and vascular resistance.

Immunohistochemical and molecular characterization of the rat 11 beta-hydroxysteroid dehydrogenase type II enzyme

Mineralocorticoid action is facilitated by 11 beta-hydroxysteroid dehydrogenase type II (11 beta HSD2), which metabolizes glucocorticoids and allows aldosterone to bind to the nonselective mineralocorticoid receptor. We have recently demonstrated the presence of the 11 beta HSD2 protein in a wide range of human epithelia, suggesting that it is the sole isoform endowing specificity in man. In the present study we have used an immunopurified polyclonal antibody (RAH23) raised against a C-terminal peptide derived from the cloned rat 11 beta HSD2 protein to perform immunohistochemical and molecular analysis in rat tissues. In frozen sections of rat kidney, strong staining was seen with the RAH23 antibody in the distal tubule; weaker staining was observed in the thick ascending loop of Henle and the medullary and papillary collecting ducts. Punctate cortical staining was observed in the fetus at 20 days gestation and in 8-day-old rats, with a noticeable increase in the staining pattern at 16 days of age. The kidney did not attain the adult pattern of staining until 28 days of age. Epithelia of ileum and colon also stained with RAH23, as did excretory ducts of the submandibular gland. Intrahepatic and excretory bile ducts displayed strong immunoreactivity in the epithelial lining. Rat adrenal glands showed evidence of the 11 beta HSD2 antigen in the zona fasciculata and zona reticularis, but not in the zona glomerulosa or medulla. Western blot analysis with the RAH23 antibody revealed strong bands in the kidney, colon, adrenal gland, and submandibular gland at 40 kDa, colinear with the migration of the cloned 11 beta HSD2 enzyme. A band of medium intensity was also seen at this size in the pancreas, whereas a band of moderate intensity was seen in the bile duct, and weaker bands were noticed in the stomach, small intestine, and liver, with a diffuse band at 36-42 kDa in the prostate. Strong bands were seen in the pancreas and prostate at 78 kDa, with weaker signals in the colon, adrenal, stomach, and bile duct. A number of tissues also displayed multiple bands at about 30 kDa. Enzymatic assays on tissue homogenates showed extensive conversion of corticosterone to its 11-dehydro product in an NAD-dependent manner in the submandibular gland, adrenal gland, and kidney, but not in the pancreas or prostate. This study confirms the ubiquitous presence of 11 beta HSD2 in sodium-transporting epithelia, demonstrates the high level of 11 beta HSD2 protein and enzyme activity in the rat adrenal, and suggests a possible role for the enzyme in the biliary system. Further studies are required to determine the relevance of the various molecular species to the activity, latency, and processing of the enzyme.

Vascular localization of the 11 beta-hydroxysteroid dehydrogenase type II enzyme

1. The enzyme 11 beta-hydroxysteroid dehydrogenase type II (11 beta HSD2) confers specificity on the non-specific mineralocorticoid receptor by converting cortisol to cortisone. 2. We have examined the localization of this enzyme in the human skin, myocardium and saphenous vein by immunohistochemical techniques. 3. High amounts of 11 beta HSD2 immunoreactivity were found in smooth muscle cells in the arterioles of the skin, heart and saphenous vein. Lower amounts of staining were also found in longitudinal and concentric smooth muscle cells lining the lumen of the saphenous vein.

The 11 beta-hydroxysteroid dehydrogenase type II enzyme: biochemical consequences of the congenital R337C mutation

The 11 beta-hydroxysteroid dehydrogenase type II enzyme (11 beta HSD2) converts cortisol to cortisone, allowing the non-selective mineralocorticoid receptor to bind aldosterone. When the activity of this enzyme is compromised, as occurs in licorice intoxication or in the congenital syndrome of apparent mineralocorticoid excess (AME), there is marked sodium retention, hypokalemia, and hypertension. The first proof that this enzyme was defective in AME came from the identification of the R337C mutation in a number of siblings with the syndrome. Subsequent expression studies showed that the mutant had a Km one order of magnitude higher than the wild-type enzyme while in the cell-free system it was without detectable activity. In the present work we have extended our studies on this mutant and provide evidence that the mutant protein may also partially inhibit the wild-type enzyme in heterozygotes. Furthermore, experiments incorporating the protein synthesis inhibitor cycloheximide show that the mutant enzyme is less stable than the wild-type activity in intact cells. These results suggest that mutations in the 11 beta HSD2 enzyme may have multiple consequences for the mineralocorticoid target cell.