Activation of the RARα Attenuated CSF Hypersecretion to Inhibit Hydrocephalus Development via Regulating the MAFB/MSR1 Pathway

Hydrocephalus has been observed in rats with spontaneous hypertension (SHRs). It has been demonstrated that activation of the oxidative stress related protein retinoic acid receptor alpha (RARα) has neuroprotective impacts. Our investigation aims to determine the potential role and mechanism of RARα in hydrocephalus. The RARα-specific agonist (Am80) and RARα inhibitor (AGN196996) were used to investigate the role of RARα in cerebrospinal fluid (CSF) secretion in the choroid plexus of SHRs. Evaluations of CSF secretion, ventricular volume, Western blotting, and immunofluorescent staining were performed. Hydrocephalus and CSF hypersecretion were identified in SHRs but not in Wistar-Kyoto rats, occurring at the age of 7 weeks. The RARα/MAFB/MSR1 pathway was also activated in SHRs. Therapy with Am80 beginning in week 5 decreased CSF hypersecretion, hydrocephalus development, and pathological changes in choroid plexus alterations by week 7. AGN196996 abolished the effect of Am80. In conclusion, activation of the RARα attenuated CSF hypersecretion to inhibit hydrocephalus development via regulating the MAFB/MSR1 pathway. RARα may act as a possible therapeutic target for hydrocephalus.

Effect of eplerenone on cognitive impairment in spontaneously hypertensive rats

OBJECTIVE

The present study aimed to determine the effect of blocking brain mineralocorticoid receptor on cognitive impairment in spontaneously hypertensive rats and its intracellular changes.

METHODS

12-week-old male spontaneous hypertensive rats (SHR) and Wistar Kyoto (WKY) rats were given eplerenone (EPL, 30 mg/Kg/d or 100 mg/Kg/d) or pure water via oral gavage daily for 8 weeks. Effects of blocking brain mineralocorticoid receptor (MR) on cognitive function were examined through cognitive behavioral experiments. The morphology of hippocampal neurons was observed. Synaptic proteins and autophagy levels were detected by western blot.

RESULTS

The results showed decreases in both short-term working memory and long-term spatial learning and memory ability, hippocampal neuron damage, and reduced expression of synaptic proteins in the SHR-Veh group. Impaired autophagy was found in the SHR-Veh group as evidenced by decreased expression levels of Beclin-1 protein and a defect in P62 degradation. These abnormalities were reversed by eplerenone, either the high dosage or low dosage. Reduced cognitive dysfunction and enhanced autophagy in hippocampal neurons in both SHR-EPL30 group and SHR-EPL100 group were independent of lowering blood pressure.

CONCLUSION

Eplerenone improves cognitive deficits observed in SHRs, and increases autophagy in hippocampal neurons of SHRs, which suggests a new site of MR antagonists in treatment of hypertension-related cognitive impairment.

Antihypertensive activity of oleanolic acid is mediated via downregulation of secretory phospholipase A2 and fatty acid synthase in spontaneously hypertensive rats

Oleanolic acid (OA) is reported to possess antihypertensive activity via the regulation of lipid metabolism; however, the mechanisms underlying lipid regulation by OA are yet to be fully elucidated. The aim of the present study was to evaluate the mechanisms via which OA regulates lipid metabolism in spontaneously hypertensive rats (SHRs) via ultra‑performance liquid chromatography‑quadrupole/Orbitrap‑mass spectrometry (MS)‑based lipidomics analysis. SHRs were treated with OA (1.08 mg/kg) for 4 weeks. The liver tissues were excised, homogenized in dichloromethane and centrifuged, and subsequently the supernatant layer was collected and concentrated under vacuum to dryness. The dichloromethane extract was subjected to MS analysis and database searching, and comparison of standards was performed to identify potential biomarkers. Partial least squares‑discriminant analysis performed on the liver lipidome revealed a total of 14 endogenous metabolites that were significantly changed in the SHR model group (SH group) compared with Wistar Kyoto rats [normal control (NC group)], including glycerophospholipids, sphingolipids and glycerides. Heatmaps revealed that the liver lipid profiles in the OA group were clustered more closely compared with those observed in the NC group, indicating that the antihypertensive effect of OA was mediated via regulation of liver lipid metabolites. It was observed that the protein levels of secretory phospholipase A2 (sPLA2) and fatty acid synthase (FAS) were increased in the SH group compared with the NC group. In addition, the levels of lysophosphatidylcholine and triglycerides in the liver were elevated, whereas the levels of low‑density lipoprotein cholesterol and high‑density lipoprotein cholesterol were reduced in the SH group. Upon treatment with OA, the mRNA and protein levels of PLA2 and FAS were observed to be downregulated. Collectively, the present study indicated that the antihypertensive activity of OA was mediated via downregulation of sPLA2 and FAS in SHRs, and that treatment with OA resulted in significant improvements in blood pressure and associated abnormalities in the lipid metabolites.

Clusterin is highly expressed in tubular complexes during spontaneous pancreatitis of spontaneous hypertensive rats

Pancreatitis is an inflammatory disorder of pancreas which leads to varying degrees of pancreatic endocrine and exocrine dysfunction and manifests in either acute or chronic forms. Spontaneous pancreatitis in experimental animals has rarely been reported. Here, we found acute to chronic courses of spontaneous pancreatitis in spontaneously hypertensive rats (SHRs), showing the formation of tubular complexes (TCs) and enhanced islet regeneration. We investigated the expression pattern of clusterin in the pancreas of SHRs based on immunohistochemistry (IHC). IHC analysis revealed the strong expression of clusterin in dedifferentiated duct-like cells and regenerative islets of TCs. These results imply that clusterin might be involved in the formation of TCs and parenchymal regeneration during rat pancreatitis.

High sucrose/fat diet and isosorbide mononitrate increase insulin resistance, nitric oxide production and myocardial apoptosis in a hypertensive rat model

The present study aimed to investigate the association between insulin resistance (IR), nitric oxide (NO) production and myocardial apoptosis in a background of coexisting hypertension in a rodent animal model. A hypertensive rat model was established by feeding Wistar and spontaneously hypertensive rats (SHR) with a high sucrose/fat (HSF) diet for 12 weeks, in conjunction with isosorbide mononitrate (ISMN). Increased IR, NO content, apoptotic gene and protein expression, and morphological alterations within rat myocardium were evaluated. Following a total of 12 weeks of feeding with HSF and ISMN resulted in increased IR and NO content within the myocardial tissue of Wistar and SHR rats. HSF and ISMN activated myocardial apoptosis by downregulating the gene transcription and protein expression levels of the anti‑apoptotic B‑cell lymphoma 2 (Bcl‑2), and increasing the pro‑apoptotic Bcl‑2 associated X protein. Apoptosis was demonstrated by DNA fragmentation in terminal deoxynucleotidyl‑transferase‑mediated dUTP nick end labelling assay. In all experiments, the combination of HSF and ISMN was associated with more pronounced effects, indicating the possible synergistic effects. In addition, the correlation analysis in the Wistar rats fed with HSF only, revealed a positive association between NO production and IR. The results of the present study indicated that HSF and ISMN simultaneously increased IR, NO production and myocardial apoptosis in the hypertensive rat model, and may therefore contribute to investigations into the long‑term clinical use of ISMN in hypertensive patients.

Quantitative analysis of hypertrophic myocardium using diffusion tensor magnetic resonance imaging

Systemic hypertension is a causative factor in left ventricular hypertrophy (LVH). This study is motivated by the potential to reverse or manage the dysfunction associated with structural remodeling of the myocardium in this pathology. Using diffusion tensor magnetic resonance imaging, we present an analysis of myocardial fiber and laminar sheet orientation in ex vivo hypertrophic (6 SHR) and normal (5 WKY) rat hearts using the covariance of the diffusion tensor. First, an atlas of normal cardiac microstructure was formed using the WKY b0 images. Then, the SHR and WKY b0 hearts were registered to the atlas. The acquired deformation fields were applied to the SHR and WKY heart tensor fields followed by the preservation of principal direction (PPD) reorientation strategy. A mean tensor field was then formed from the registered WKY tensor images. Calculating the covariance of the registered tensor images about this mean for each heart, the hypertrophic myocardium exhibited significantly increased myocardial fiber derangement ([Formula: see text]) with a mean dispersion of 38.7 deg, and an increased dispersion of the laminar sheet normal ([Formula: see text]) of 54.8 deg compared with 34.8 deg and 51.8 deg, respectively, in the normal hearts. Results demonstrate significantly altered myocardial fiber and laminar sheet structure in rats with hypertensive LVH.

Role of SDF-1 and Wnt signaling pathway in the myocardial fibrosis of hypertensive rats

OBJECTIVE

To investigate the effects of stromal cell-derived factor-1 (SDF-1) and Wnt signaling pathway on the bioactivities of myofibroblasts (MFs) and the expressions of SDF-1 and components of Wnt signaling pathway in the myocardium of spontaneously hypertensive rats (SHR).

METHODS

BMSCs were induced to differentiate into MFs in vitro, and SDF-1 and Wnt signaling pathway were independently or simultaneously blocked. Then, the migration of MFs and the secretion of Col I and α-SMA were determined in MFs. Heart function, progression of myocardial fibrosis and structure of the heart were evaluated. The expression of SDF-1 and components of Wnt signaling pathway in SHR was detected.

RESULTS

TGF-β could induce the differentiation of BMSCs into B-MFs; Blocking SDF-1/CXCR4 axis and/or Wnt signaling pathway was able to inhibit the MFs migration and Col I secretion; Blocking Wnt signaling pathway inhibited the differentiation of BMSCs into MFs; Serum SDF-1 increased with the increase in blood pressure, and serum β-catenin elevated with the fluctuation of blood pressure; Protein and mRNA expressions of SDF-1 in the myocardium increased, and those of DKK-1 (an inhibitor of Wnt signaling pathway) and GSK-3 reduced in SHR.

CONCLUSION

SDF-1 and Wnt signaling pathway are involved in the differentiation of BMSCs into MFs, as well as the migration and collagen secretion of MFs; Hypertension affects the expressions of SDF-1 and components of Wnt signaling pathway. In the myocardium of SHR, SDF-1 expression increases, but the expression of inhibitor of Wnt signaling pathway reduces.

Improved trabecular bone structure of 20-month-old male spontaneously hypertensive rats

A few clinical studies have reported that elderly male participants with hypertensive disease frequently have higher bone mineral density (BMD) than the normotensive participants at several skeletal sites. The detailed mechanism is still unknown; therefore, a study of bone structure and density using the hypertensive animal models could be informative. We used micro-computed tomography to quantitatively evaluate the tibial and 3rd lumbar vertebral bones in the 20-month-old male spontaneous hypertensive rat (SHR). The BMD, volume fraction, and the microarchitecture changes of the SHR were compared to those of same-age normotensive controls (Wistar-Kyoto rat, WKY). We found that in the very old (20 month) male rats, the trabecular bone fraction and microstructure were higher than those in the same-age normotensive controls. The observation of the association of hypertension with BMD and bone strength in hypertensive rats warrants further investigations of bone mass and strength in elderly males with hypertension.

ACE inhibition reduces infarction in normotensive but not hypertensive rats: correlation with cortical ACE activity

Angiotensin-converting enzyme (ACE) inhibition can reduce stroke risk by up to 43% in humans and reduce the associated disability, and hence understanding the mechanism of improvement is important. In animals and humans, these effects may be independent of the blood pressure-lowering effects of ACE inhibition. Normotensive (Wistar-Kyoto (WKY)) and hypertensive (spontaneously hypertensive rat (SHR)) animals were treated with the ACE inhibitors ramipril or lisinopril for 7 or 42 days before 2 hours of transient middle cerebral artery occlusion (MCAo). Blood pressure, serum ACE, and blood glucose levels were measured and stroke infarct volume was recorded 24 hours after stroke. Despite greater reductions in blood pressure, infarct size was not improved by ACE inhibition in hypertensive animals. Short-term ACE inhibition produced only a modest reduction in blood pressure, but WKY rats showed marked reductions in infarct volume. Long-term ACE inhibition had additional reductions in blood pressure; however, infarct volumes in WKY rats did not improve further but worsened. WKY rats differed from SHR in having marked cortical ACE activity that was highly sensitive to ACE inhibition. The beneficial effects of ACE inhibition on infarct volume in normotensive rats do not correlate with changes in blood pressure. However, WKY rats have ACE inhibitor-sensitive cortical ACE activity that is lacking in the SHR.