Maternal adaptation in pregnant hypertensive rats: improvement of vascular and inflammatory variables and oxidative damage in the kidney

Prediction of the mechanisms of action of Shenkang in chronic kidney disease: A network pharmacology study and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine provides a unique curative treatment of complex chronic diseases, including chronic kidney disease (CKD), which is not effectively treated with the current therapies. The pharmacological mechanisms of Shenkang (SK), a herbal medicine containing rhubarb (Rheum palmatum L. or R. tanguticum Maxim. ex Balf.), red sage (Salvia miltiorrhiza Bunge), safflower (Carthamus tinctorius L.), and astragalus (Astragalus mongholicus Bunge), widely used to treat CKD in China, are still unclear.

AIM OF THE STUDY

In this study, the comprehensive approach used for elucidating the pharmacological mechanisms of SK included the identification of the effective constituents, target prediction and network analysis, by investigating the interacting pathways between these molecules in the context of CKD. These results were validated by performing an in vivo study and by comparison with literature reviews.

MATERIALS AND METHODS

This approach involved the following main steps: first, we constructed a molecular database for SK and screened for active molecules by conducting drug-likeness and drug half-life evaluations; second, we used a weighted ensemble similarity drug-targeting model to accurately identify the direct drug targets of the bioactive constituents; third, we constructed compound-target, target-pathway, and target-disease networks using the Cytoscape 3.2 software and determined the distribution of the targets in tissues and organs according to the BioGPS database. Finally, the resulting drug-target mechanisms were compared with those proposed by previous research on SK and validated in a mouse model of CKD.

RESULTS

By using Network analysis, 88 potential bioactive compounds in the four component herbs of SK and 85 CKD-related targets were identified, including pathways that involve the nuclear factor-κB, mitogen-activated protein kinase, transient receptor potential, and vascular endothelial growth factor, which were categorized as inflammation, proliferation, migration, and permeability modules. The results also included different tissues (kidneys, liver, lungs, and heart) and different disease types (urogenital, metabolic, endocrine, cardiovascular, and immune diseases as well as pathological processes) closely related to CKD. These findings agreed with those reported in the literature. However, our findings with the network pharmacology prediction did not account for all the effects reported for SK found in the literature, such as regulation of the hemodynamics, inhibition of oxidative stress and apoptosis, and the involvement of the transforming growth factor-β/SMAD3, sirtuin/forkhead box protein O (SIRT/FOXO) and B-cell lymphoma-2-associated X protein pathways. The in vivo validation experiment revealed that SK ameliorated CKD through antifibrosis and anti-inflammatory effects, by downregulating the levels of vascular cell adhesion protein 1, vitamin D receptor, cyclooxygenase-2, and matrix metalloproteinase 9 proteins in the unilateral ureteral obstruction mouse model. This was consistent with the predicted target and pathway networks.

CONCLUSIONS

SK exerted a curative effect on CKD and CKD-related diseases by targeting different organs, regulating inflammation and proliferation processes, and inhibiting abnormal extracellular matrix accumulation. Thus, pharmacological network analysis with in vivo validation explained the potential effects and mechanisms of SK in the treatment of CKD. However, these findings need to be further confirmed with clinical studies.

Stimulation of the ACE2/Ang-(1-7)/Mas axis in hypertensive pregnant rats attenuates cardiovascular dysfunction in adult male offspring

The aim of this study was to investigate whether treatment with diminazene aceturate (DIZE), a putative ACE2 activator, or with angiotensin-(1-7) during pregnancy could attenuate the development of cardiovascular dysfunction in the adult offspring of spontaneously hypertensive rats (SHRs). For this, pregnant SHRs received DIZE or Ang-(1-7) throughout gestation. The systolic blood pressure (SBP) was measured in the male offspring from the 6th to16th weeks of age by tail-cuff plethysmography. Thereafter, the left ventricular contractile function and coronary reactivity were evaluated by the Langendorff technique. Samples of the left ventricles (LVs) and kidneys were collected for histology and western blot assay in another batch of adult rat offspring. Maternal treatment with DIZE or Ang-(1-7) during pregnancy attenuated the increase in SBP in adult offspring. In addition, both DIZE and Ang-(1-7) treatments reduced the cardiomyocyte diameter and fibrosis deposition in the LV, and treatment with Ang-(1-7) also reduced the fibrosis deposition in the kidneys. Maternal treatment with DIZE, as well as Ang-(1-7), improved the coronary vasodilation induced by bradykinin in isolated hearts from adult offspring. However, no difference was observed in the contractile function of the LVs of these animals. The expression levels of AT1 and Mas receptors, ACE, ACE2, SOD, and catalase in the LV were not modified by maternal treatment with Ang-(1-7), but this treatment elicited a reduction in AT2 expression. These data show that treatment with DIZE or Ang-(1-7) during gestation promoted beneficial effects of attenuating hypertension and cardiac remodeling in adult offspring.

The Dahl salt-sensitive rat is a spontaneous model of superimposed preeclampsia

The mechanisms of the pathogenesis of preeclampsia, a leading cause of maternal morbidity and death worldwide, are poorly understood in part due to a lack of spontaneous animal models of the disease. We hypothesized that the Dahl salt-sensitive (S) rat, a genetic model of hypertension and kidney disease, is a spontaneous model of superimposed preeclampsia. The Dahl S was compared with the Sprague-Dawley (SD) rat, a strain with a well-characterized normal pregnancy, and the spontaneously hypertensive rat (SHR), a genetic model of hypertension that does not experience a preeclamptic phenotype despite preexisting hypertension. Mean arterial pressure (MAP, measured via telemetry) was elevated in the Dahl S and SHR before pregnancy, but hypertension was exacerbated during pregnancy only in Dahl S. In contrast, SD and SHR exhibited significant reductions in MAP consistent with normal pregnancy. Dahl S rats exhibited a severe increase in urinary protein excretion, glomerulomegaly, increased placental hypoxia, increased plasma soluble fms-like tyrosine kinase-1 (sFlt-1), and increased placental production of tumor necrosis factor-α (TNF-α). The Dahl S did not exhibit the expected decrease in uterine artery resistance during late pregnancy in contrast to the SD and SHR. Dahl S pups and litter sizes were smaller than in the SD. The Dahl S phenotype is consistent with many of the characteristics observed in human superimposed preeclampsia, and we propose that the Dahl S should be considered further as a spontaneous model to improve our understanding of the pathogenesis of superimposed preeclampsia and to identify and test new therapeutic targets for its treatment.

Pregnant rats treated with a high-fat/prooxidant Western diet with ANG II and TNF-α are resistant to elevations in blood pressure and renal oxidative stress

Oxidative stress and inflammation are risk factors for hypertension in pregnancy. Here, we examined the 24-h mean arterial pressure (MAP) via telemetry and the nitric oxide (NO) and redox systems in the kidney cortex, medulla, and aorta of virgin and pregnant rats treated with a high-fat/prooxidant Western diet (HFD), ANG II, and TNF-α. Female Sprague-Dawley rats were given a normal diet (ND) or a HFD for 8 wk before mating. Day 6 of pregnancy and age-matched virgins were implanted with minipumps infusing saline or ANG II (150 ng·kg(-1)·min(-1)) + TNF-α (75 ng/day) for 14 days. Groups consisted of Virgin + ND + Saline (V+ND) (n = 7), Virgin + HFD +ANG II and TNF-α (V+HFD) (n = 7), Pregnant + ND + Saline (P+ND) (n = 6), and Pregnant + HFD + ANG II and TNF-α (P+HFD) (n = 8). After day 6 of minipump implantation, V+HFD rats displayed an increase in MAP on days 7, 8, and 10-15 vs. V+ND rats. P+HFD rats, after day 6 of minipump implantation, showed an increase in MAP only on day 7 vs. P+ND rats. P+HFD rats had a normal fall in 24-h MAP, hematocrit, plasma protein concentration, and osmolality at late pregnancy. No change in kidney cortex, medulla, or aortic oxidative stress in P+HFD rats. P+HFD rats displayed a decrease in nNOSβ abundance, but no change in kidney cortex NOx content vs. P+ND rats. Pregnant rats subjected to a chronic HFD and prooxidant and proinflammatory insults have a blunted increase in 24-h MAP and renal oxidative stress. Our data suggest renal NO bioavailability is not altered in pregnant rats treated with a HFD, ANG II, and TNF-α.

Role of Inflammation and the Angiotensin Type 2 Receptor in the Regulation of Arterial Pressure During Pregnancy in Mice

During normal pregnancy the renin–angiotensin system is activated, yet pregnant women are resistant to the pressor effects of angiotensin II. Our aim was to determine the role of the angiotensin type 2 receptor (AT 2 R) in the regulation of arterial pressure, natriuresis, and immune cell infiltration during pregnancy. Mean arterial pressure was measured via telemetry, and flow cytometry was used to enumerate immune cell infiltration in 14-week-old wild-type and AT 2 R knockout mice during gestation. In wild-type mice, mean arterial pressure decreased during gestation, reaching a nadir at gestational day 9 (–6±2 mm Hg) and returned to near preconception levels during late gestation. In AT 2 R-deficient mice, the midgestational decrease in mean arterial pressure was absent. Furthermore, mean arterial pressure was significantly increased during late gestation compared with wild-type mice (≈10 mm Hg). As expected, circulating immune cell activation was suppressed during pregnancy. However, this response was absent in AT 2 R-deficient mice. While renal immune cell infiltration was similar between the genotypes, there was a significant T cell phenotypic switch toward a proinflammatory T-helper 1 phenotype in AT 2 R-deficient mice. These data indicate that the AT 2 R plays an important role in arterial pressure regulation and may modulate T cell activation and renal cytokine production during pregnancy. Therefore, deficits in AT 2 R expression may contribute to pregnancy-induced hypertension and thus represents a potential therapeutic target.

Targeting inflammation: new therapeutic approaches in chronic kidney disease (CKD)

Chronic inflammation and oxidative stress, features that are closely associated with nuclear factor (NF-κB) activation, play a key role in the development and progression of chronic kidney disease (CKD). Several animal models and clinical trials have clearly demonstrated the effectiveness of angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) therapy to improve glomerular/tubulointerstitial damage, reduce proteinuria, and decrease CKD progression, but CKD treatment still represents a clinical challenge. Bardoxolone methyl, a first-in-class oral Nrf-2 (nuclear factor erythroid 2-related factor 2) agonist that until recently showed considerable potential for the management of a range of chronic diseases, had been shown to improve kidney function in patients with advanced diabetic nephropathy (DN) with few adverse events in a phase 2 trial, but a large phase 3 study in patients with diabetes and CKD was halted due to emerging toxicity and death in a number of patients. Instead, palmitoylethanolamide (PEA) a member of the fatty acid ethanolamine family, is a novel non-steroidal, kidney friendly anti-inflammatory and anti-fibrotic agent with a well-documented safety profile, that may represent a potential candidate in treating CKD probably by a combination of pharmacological properties, including some activity at the peroxisome proliferator activated receptor alpha (PPAR-α). The aim of this review is to discuss new therapeutic approaches for the treatment of CKD, with particular reference to the outcome of two therapies, bardoxolone methyl and PEA, to improve our understanding of which pharmacological properties are responsible for the anti-inflammatory effects necessary for the effective treatment of renal disease.

Effect of transverse aortic constriction on cardiac structure, function and gene expression in pregnant rats

Background

There is an increased risk of heart failure and pulmonary edema in pregnancies complicated by hypertensive disorders. However, in a previous study we found that pregnancy protects against fibrosis and preserves angiogenesis in a rat model of angiotensin II induced cardiac hypertrophy. In this study we test the hypothesis that pregnancy protects against negative effects of increased afterload.

Methods

Pregnant (gestational day 5.5–8.5) and non-pregnant Wistar rats were randomized to transverse aortic constriction (TAC) or sham surgery. After 14.2±0.14 days echocardiography was performed. Aortic blood pressure and left ventricular (LV) pressure-volume loops were obtained using a conductance catheter. LV collagen content and cardiomyocyte circumference were measured. Myocardial gene expression was assessed by real-time polymerase chain reaction.

Results

Heart weight was increased by TAC (p<0.001) but not by pregnancy. Cardiac myocyte circumference was larger in pregnant compared to non-pregnant rats independent of TAC (p = 0.01), however TAC per se did not affect this parameter. Collagen content in LV myocardium was not affected by pregnancy or TAC. TAC increased stroke work more in pregnant rats (34.1±2.4 vs 17.5±2.4 mmHg/mL, p<0.001) than in non-pregnant (28.2±1.7 vs 20.9±1.5 mmHg/mL, p = 0.06). However, it did not lead to overt heart failure in any group. In pregnant rats, α-MHC gene expression was reduced by TAC. Increased in the expression of β-MHC gene was higher in pregnant (5-fold) compared to non-pregnant rats (2-fold) after TAC (p = 0.001). Nine out of the 19 genes related to cardiac remodeling were affected by pregnancy independent of TAC.

Conclusions

This study did not support the hypothesis that pregnancy is cardioprotective against the negative effects of increased afterload. Some differences in cardiac structure, function and gene expression between pregnant and non-pregnant rats following TAC indicated that afterload increase is less tolerated in pregnancy.

Renal redox response to normal pregnancy in the rat

Normal pregnancy involves increased renal sodium reabsorption, metabolism, and oxygen consumption, which can cause increased oxidative stress (OS). OS can decrease nitric oxide (NO) bioavailability and cause pregnancy complications. In this study we examined the NO synthases (NOS) and redox state in the kidney cortex and aorta in early (E), mid (M), and late (L) pregnant (P) (days 3, 12, 20) and 2-4 days postpartum (PP) rats compared with virgin rats (V). Protein abundance of endothelial NOS (eNOS) was unchanged and neuronal NOS (nNOS)α fell at LP in the kidney cortex. Kidney cortex nNOSβ was elevated at MP, LP, and PP. No changes in aortic NOS isoforms were observed. Kidney cortex nitrotyrosine (NT) abundance decreased in EP, MP, and PP, whereas aortic NT increased in EP, MP, and PP. The NADPH oxidase subunit p22phox decreased in the kidney cortex at EP while aortic p22phox increased in EP and LP. No changes in kidney cortex NADPH-dependent superoxide production or hydrogen peroxide levels were noted. Kidney cortex cytosolic (CuZn) superoxide dismutase (SOD) was unchanged, while mitochondrial SOD decreased at EP and extracellular SOD decreased at MP and LP in the kidney cortex. Despite falls in abundance of kidney cortex SODs, total antioxidant capacity (TAC) was elevated in EP, MP, and PP in the kidney cortex. Aortic CuZn SOD deceased at PP, while the other aortic SODs and aortic TAC did not change. Data from this study suggest that the kidney cortex is protected from OS during normal rat pregnancy via an increase in antioxidant activity.

GPCRs as potential therapeutic targets in preeclampsia

Preeclampsia is an important obstetric complication that arises in 5% of women after the 20(th) week of gestation, for which there is no specific therapy and no cure. Although much of the recent investigation in this field has focused on soluble forms of the angiogenic membrane receptor tyrosine kinase Flt1 and the transforming growth factor β co-receptor Endoglin, there is significant clinical potential for several GPCR targets and their agonists or antagonists in preeclampsia. In this review, we discuss several of the most promising candidates in this category, including calcitonin receptor-like receptor / receptor activity modifying protein 1 complexes, the angiotensin AT1, 2 and Mas receptors, and the relaxin receptor RXFP1. We also address some of the controversies surrounding the roles and therapeutic potential of these GPCRs and their (ant)agonists in preeclampsia.

Role of renin-angiotensin system and oxidative status on the maternal cardiovascular regulation in spontaneously hypertensive rats

BACKGROUND

The purpose of this study was to investigate the contribution of renin-angiotensin system (RAS) and oxidative status on the maternal cardiovascular regulation at the end of pregnancy in normotensive and spontaneously hypertensive rats (SHR).

METHODS

Blood pressure (BP), mesenteric arterial bed (MAB) reactivity, mesenteric oxidative damage, protein expression, and antioxidant activities were compared between four groups: SHR (SHR-P) and normotensive Wistar controls (W-P) in the 20th day of pregnancy or age-matched nonpregnant rats (SHR-NP and W-NP).

RESULTS

BP in W-P and SHR-P was reduced at the end of pregnancy. The vasodilator effects of angiotensin II (Ang II) and angiotensin 1-7 (Ang-(1-7)) were higher in SHR-P than in other groups. Endothelial nitric oxide synthase (eNOS) expression was increased in W-P and SHR-P compared to nonpregnant groups. Angiotensin-converting enzyme (ACE) and AT(1) receptor expressions were increased in SHR-NP compared to normotensive groups and pregnancy reduced their expressions in SHR. No difference was observed in AT(2) receptor expression among the groups. ACE2 expression was higher in hypertensive than normotensive groups. The levels of thiobarbituric acid-reactive substances (TBARS) were reduced in pregnant compared to nonpregnant groups. Superoxide dismutase (SOD) activity was reduced in SHR-P compared to SHR-NP. However, pregnancy increased catalase (CAT) and glutathione peroxidase (GPx) activities in normotensive rats and SHR, respectively.

CONCLUSIONS

The results suggest that the reduction of BP to normal values at the end of pregnancy in SHR may be related to an increased NO production and vasorelaxation to Ang II and Ang-(1-7) associated with decreased expression of vascular ACE and AT(1) receptors and oxidative status.

Chemokine and free fatty acid levels in insulin-resistant state of successful pregnancy: a preliminary observation

Increased insulin resistance and inflammatory action are observed in pregnancy-induced hypertension (PIH), but similar insulin resistance is observed also in successful pregnancy. To estimate insulin resistance and inflammatory activity in normal pregnancy and PIH, serum concentrations of free fatty acids (FFA; corrected with albumin to estimate unbound FFA), monocyte chemoattractant protein (MCP)-1, and high-molecular weight (HMW) adiponectin were measured in severe PIH patients with a BMI less than 25 kg/m² and were measured 3 times during the course of pregnancy in women with normal pregnancies. FFA/albumin, MCP-1, and HMW adiponectin concentrations were significantly higher in PIH patients than in women with normal pregnancies. The 3 measurements of FFA/albumin showed a significant increase through the course of uncomplicated pregnancies. In contrast, MCP-1 and HMW adiponectin were significantly decreased during the course of pregnancy. These results suggest that the reduced MCP-1 concentration in normal pregnancy may be a pathway to inhibit the induction of pathological features from physiological insulin resistance and homeostatic inflammation.

Characterization of the L-arginine-NO-cGMP pathway in spontaneously hypertensive rat platelets: the effects of pregnancy

Nitric oxide (NO) is a short-lived intercellular messenger that provides an efficient vascular regulatory mechanism to support homeostasis and prevent thrombosis. Endothelial dysfunction and reduced NO bioavailability have a central role in hypertension associated with pregnancy. The purpose of this study was to investigate the impact of pregnancy on the L-arginine-NO-cGMP pathway in platelets and its correlation to platelet function and blood pressure in normotensive rats and spontaneously hypertensive rats (SHRs). Platelets were obtained from blood on the 20th day of pregnancy from female SHRs (SHR-P) and normotensive controls (P) or age-matched nonpregnant rats (SHR-NP and NP). Intraplatelet NO synthase (NOS) activity was reduced in P compared to NP, despite unchanged L-arginine influx. The expression levels of endothelial NOS (eNOS) and inducible NOS (iNOS) were diminished during pregnancy in normotensive rats. Paradoxically, cyclic guanosine monophosphate (cGMP) levels were similar between NP and P, as were phosphodiesterase type 5 (PDE5) expression and platelet aggregation induced by adenosine diphosphate. In SHRs, L-arginine influx was reduced in SHR-P compared to SHR-NP. SHR-P exhibited impaired NOS activity and reduced iNOS expression compared with SHR-NP. Soluble guanylyl cyclase and PDE5 expression in platelets were lower in SHR-P than in SHR-NP, whereas no differences were noted between groups with respect to cGMP levels. However, increased levels of cGMP were observed in SHR-P compared to normotensive groups and platelet aggregability remained unaltered. In conclusion, these observations prompted the hypothesis that normal platelet aggregation in pregnant SHRs may be related to a reduction in PDE5 expression and consequently the maintenance of cGMP levels, independently of reduced platelet NO bioavailability.