Kidney pathology precedes and predicts the pathological cascade of cerebrovascular lesions in stroke prone rats

Genotypes of Stim1 and the proximal region on chromosome 1 exert opposite effects on stroke susceptibility in stroke-prone spontaneously hypertensive rat

BACKGROUND

The stroke-prone spontaneously hypertensive rat (SHRSP) is a genetic model for cerebral stroke. Although a recent study on a congenic SHRSP suggested that a nonsense mutation in stromal interaction molecule 1 ( Stim1 ) encoding a major component of store-operated Ca 2+ entry was a causal variant for stroke in SHRSP, this was not conclusive because the congenic region including Stim1 in that rat was too wide. On the other hand, we demonstrated that the Wistar-Kyoto (WKY)-derived congenic fragment adjacent to Stim1 exacerbated stroke susceptibility in a congenic SHRSP called SPwch1.71. In the present study, we directly examined the effects of the Stim1 genotype on stroke susceptibility using SHRSP in which wild-type Stim1 was knocked in (called Stim1 -KI SHRSP). The combined effects of Stim1 and the congenic fragment of SPwch1.71 were also investigated.

METHODS

Stroke susceptibility was assessed by the stroke symptom-free and survival periods based on observations of behavioral symptoms and reductions in body weight.

RESULTS

Stim1 -KI SHRSP was more resistant to, while SPwch1.71 was more susceptible to stroke than the original SHRSP. Introgression of the wild-type Stim1 of Stim1 -KI SHRSP into SPwch1.71 by the generation of F1 rats ameliorated stroke susceptibility in SPwch1.71. Gene expression, whole-genome sequencing, and biochemical analyses identified Art2b , Folr1 , and Pde2a as possible candidate genes accelerating stroke in SPwch1.71.

CONCLUSION

The substitution of SHRSP-type Stim1 to wild-type Stim1 ameliorated stroke susceptibility in both SHRSP and SPwch1.71, indicating that the nonsense mutation in Stim1 is causally related to stroke susceptibility in SHRSP.

Integrated gut microbiota and serum metabolomics reveal the protective effect of oleanolic acid on liver and kidney-injured rats induced by Euphorbia pekinensis

Euphorbia pekinensis (EP) is a commonly used Chinese medicine treating edema with potential hepatorenal toxicity. However, its toxic mechanism and prevention are remained to be explored. Oleanolic acid (OA) is a triterpene acid with potential hepatorenal protective activities. We investigated the protective effect and potential mechanism of OA on EP-induced hepatorenal toxicity. In this study, rats were given total diterpenes from EP (TDEP, 16 mg/kg) combined with OA (10, 20, 40 mg/kg) by gavage for 4 weeks. The results showed that TDEP administration could lead to a 3-4-fold increasement in hepatorenal biochemical parameters with histopathological injuries, while OA treatment could ameliorate them in a dose-dependent manner. At microbial and metabolic levels, intestinal flora and host metabolism were perturbed after TDEP administration. The disturbance of bile acid metabolism was the most significant metabolic pathway, with secondary bile acids increasing while conjugated bile acids decreased. OA treatment can improve the disorder of intestinal flora and metabolic bile acid spectrum. Further correlation analysis screened out that Escherichia-Shigella, Phascolarctobacterium, Acetatifactor, and Akkermansia were closely related to the bile acid metabolic disorder. In conclusion, oleanolic acid could prevent hepatorenal toxicity induced by EP by regulating bile acids metabolic disorder via intestinal flora improvement.

A 3-Mbp fragment on rat chromosome 1 affects susceptibility both to stroke and kidney injury under salt loading in the stroke-prone spontaneously hypertensive rat: a genetic approach using multiple congenic strains

We have previously reported that a major quantitative trait locus (QTL) responsible for susceptibility to salt-induced stroke in the stroke-prone spontaneously hypertensive rat (SHRSP) is located in a 3-Mbp region on chromosome 1 covered by SHRSP.SHR-(D1Rat23-D1Rat213)/Izm (termed Pr1.31), a congenic strain with segments from SHRSP/Izm introduced into the stroke-resistant SHR/Izm. Here, we attempted to narrow down the candidate region on chromosome 1 further through analyses of subcongenic strains constructed for the target region. Simultaneously, salt-induced kidney injury was evaluated through the measurement of urinary albumin and the gene expression of renal tubular injury markers (Kim-1 and Clu) to explore a possible mechanism leading to the onset of stroke. All subcongenic strains examined in this study showed lower susceptibility to salt-induced stroke than SHRSP. Interestingly, Pr1.31 had the lowest stroke susceptibility when compared with newly constructed subcongenic strains harboring fragments of the congenic sequence in Pr1.31. Although Kim-1 and Clu expression after 1 week of salt loading in Pr1.31 did not differ significantly from those in SHRSP, the urinary albumin level of Pr1.31 was significantly lower than those of the other subcongenic strains and that of SHRSP. The present results indicated that, although the congenic fragment in Pr1.31 harbored the gene(s) related to salt-induced organ damages, further genetic dissection of the candidate region was difficult due to multiple QTLs suggested in this region. Further analysis using Pr1.31 will unveil genetic and pathophysiological mechanisms underlying salt-induced end organ damages in SHRSP.

Relaxin Attenuates Organ Fibrosis via an Angiotensin Type 2 Receptor Mechanism in Aged Hypertensive Female Rats

Background

The antifibrotic effects of recombinant human relaxin (RLX) in the kidney are dependent on an interaction between its cognate receptor (RXFP1) and the angiotensin type 2 receptor (AT₂R) in male models of disease. Whether RLX has therapeutic effects, which are also mediated via AT₂R, in hypertensive adult and aged/reproductively senescent females is unknown. Thus, we determined whether treatment with RLX provides cardiorenal protection via an AT₂R-dependent mechanism in adult and aged female stroke-prone spontaneously hypertensive rats (SHRSPs).

Methods

In 6-month-old (6MO) and 15-month-old ([15MO]; reproductively senescent) female SHRSP, systolic BP (SBP), GFR, and proteinuria were measured before and after 4 weeks of treatment with vehicle (Veh), RLX (0.5 mg/kg per day s.c.), or RLX+PD123319 (AT₂R antagonist; 3 mg/kg per day s.c.). Aortic endothelium-dependent relaxation and fibrosis of the kidney, heart, and aorta were assessed.

Results

In 6MO SHRSP, RLX significantly enhanced GFR by approximately 25% (P=0.001) and reduced cardiac fibrosis (P=0.01) as compared with vehicle-treated counterparts. These effects were abolished or blunted by PD123319 coadministration. In 15MO females, RLX reduced interstitial renal (P=0.02) and aortic (P=0.003) fibrosis and lowered SBP (13±3 mm Hg; P=0.04) relative to controls. These effects were also blocked by PD123319 cotreatment (all P=0.05 versus RLX treatment alone). RLX also markedly improved vascular function by approximately 40% (P<0.001) in 15MO SHRSP, but this was not modulated by PD123319 cotreatment.

Conclusions

The antifibrotic and organ-protective effects of RLX, when administered to a severe model of hypertension, conferred cardiorenal protection in adult and reproductively senescent female rats to a great extent via an AT₂R-mediated mechanism.

Brain Overexpression of Uncoupling Protein-2 (UCP2) Delays Renal Damage and Stroke Occurrence in Stroke-Prone Spontaneously Hypertensive Rats

The downregulation of uncoupling protein-2 (UCP2) is associated with increased brain and kidney injury in stroke-prone spontaneously hypertensive rats (SHRSP) fed with a Japanese style hypersodic diet (JD). Systemic overexpression of UCP2 reduces organ damage in JD-fed SHRSP. We examined the effect of brain-specific UCP2 overexpression on blood pressure (BP), stroke occurrence and kidney damage in JD-fed SHRSP. Rats received a single i.c.v. injection of a lentiviral vector encoding UCP2 (LV-UCP2), or an empty vector. The brain delivery of LV-UCP2 significantly delayed the occurrence of stroke and kidney damage. The large reduction of proteinuria observed after LV-UCP2 injection was unexpected, because BP levels were unchanged. At the time of stroke, rats treated with LV-UCP2 still showed a large UCP2 upregulation in the striatum, associated with increases in OPA1 and FIS1 protein levels, and reductions in PGC1-α, SOD2, TNFα mRNA levels and NRF2 protein levels. This suggested UCP2 overexpression enhanced mitochondrial fusion and fission and reduced oxidative damage and inflammation in the striatum of JD-fed SHRSP rats. Our data suggest the existence of central mechanisms that may protect against hypertension-induced organ damage independently of BP, and strengthen the suitability of strategies aimed at enhancing UCP2 expression for the treatment of hypertensive damage.

Whey Protein and Its Components Lactalbumin and Lactoferrin Affect Energy Balance and Protect against Stroke Onset and Renal Damage in Salt-Loaded, High-Fat Fed Male Spontaneously Hypertensive Stroke-Prone Rats

BACKGROUND

Whey protein (WH)-enriched diets are reported to aid in weight loss and to improve cardiovascular health. However, the bioactive components in whey responsible for causing such effects remain unidentified.

OBJECTIVE

We determined the effects of whey and its components [α-lactalbumin (LA) and lactoferrin (LF)] on energy balance, glucose tolerance, gut hormones, renal damage, and stroke onset in rats.

METHODS

Male spontaneously hypertensive stroke-prone (SHRSP) rats (age 8 wk) were fed isocaloric high-fat (40% kcal) and high-salt (4% wt/wt) diets (n = 8-10/group) and randomized for 8 wk to diets enriched as follows: control (CO): 15% kcal from egg albumin, 45% kcal from carbohydrate; WH: 20%kcal WH isolate + 15% kcal egg albumin; LA: 20% kcal LA  + 15% kcal egg albumin; or LF: 20% kcal lactoferrin + 15% kcal egg albumin. Measurements included energy balance (food intake, energy expenditure, and body composition), stroke-related behaviors, brain imaging, glucose tolerance, metabolic hormones, and tissue markers of renal damage. Data were analyzed by linear mixed models with repeated measures or 1-way ANOVA.

RESULTS

Diets enriched with WH, LA, or LF increased survival, with 25% of rats fed these diets exhibiting stroke-associated morbidity, whereas 90% of CO rats were morbid by 8 wk (P < 0.05). The nephritis scores of rats fed WH-, LA-, or LF-enriched diets were 80%, 92%, and 122% lower than those of COs (P = 0.001). The mRNA abundances of renin and osteopontin were 100-600% lower in rats fed WH-, LA-, or LF-enriched diets than in COs (P < 0.05). Urine albumin concentrations and albumin-to-creatinine ratios were 200% lower in rats fed LF-enriched diets than in COs (P < 0.05). Compared with COs, rats fed LF-enriched diets for 2-3 wk had food intake decreased by 29%, body weight decreased by 13-19%, lean mass decreased by 12-19%, and fat mass decreased by 20% (P < 0.001). Relative to COs, rats fed WH and LA had food intake decreased by 10% (P < 0.1), but COs had 12-45% lower weight than rats fed LA- and WH-enriched diets by 3 wk (P < 0.01). Compared with COs, rats fed WH-enriched diets increased energy expenditure by 7%, whereas, rats fed LA-enriched diets had energy expenditure acutely decreased by 7% during the first 4 d, and rats fed LF-enriched diets had energy expenditure decreased by 7-17% throughout the first week ( P < 0.001). Rats fed LA- and LF-enriched diets had blood glucose decreased by 14-19% (P < 0.05) and WH by 9% (P = 0.1), relative to COs. Compared with COs, rats fed LF had GIP decreased by 90% and PYY by 87% (P < 0.05).

CONCLUSION

Together, these findings indicate that whey and its components α-lactalbumin and lactoferrin improved energy balance and glycemic control, and protected against the onset of neurological deficits associated with stroke and renal damage in male SHRSP rats.

Pharmacological restoration of autophagy reduces hypertension-related stroke occurrence

The identification of the mechanisms predisposing to stroke may improve its preventive and therapeutic strategies in patients with essential hypertension. The role of macroautophagy/autophagy in the development of hypertension-related stroke needs to be clarified. We hypothesized that a defective autophagy may favor hypertension-related spontaneous stroke by promoting mitochondrial dysfunction. We studied autophagy in the stroke-prone spontaneously hypertensive (SHRSP) rat, which represents a clinically relevant model of stroke associated with high blood pressure. We assessed autophagy, mitophagy and NAD⁺:NADH levels in brains of SHRSP and stroke-resistant SHR fed with high salt diet. Vascular smooth muscle cells silenced for the mitochondrial complex I subunit Ndufc2 gene (NADH:ubiquinone oxidoreductase subunit C2) and cerebral endothelial cells isolated from SHRSP were also used to assess autophagy/mitophagy and mitochondrial function in response to high salt levels. We found a reduction of autophagy in brains of high salt-fed SHRSP. Autophagy impairment was associated with NDUFC2 downregulation, mitochondrial dysfunction and NAD⁺ depletion. Restoration of NAD⁺ levels by nicotinamide administration reactivated autophagy and reduced stroke development in SHRSP. A selective reactivation of autophagy/mitophagy by Tat-Beclin 1 also reduced stroke occurrence, restored autophagy/mitophagy and improved mitochondrial function. Endothelial progenitor cells (EPCs) from subjects homozygous for the thymine allele variant at NDUFC2/rs11237379, which is associated with NDUFC2 deficiency and increased stroke risk, displayed an impairment of autophagy and increased senescence in response to high salt levels. EPC senescence was rescued by Tat-Beclin 1. Pharmacological activation of autophagy may represent a novel therapeutic strategy to reduce stroke occurrence in hypertension.

ABBREVIATIONS

10 VSMCs: aortic vascular smooth muscle cells; COX4I1/COX IV: cytochrome c oxidase subunit 4I1; ECs: endothelial cells; EPCs: endothelial progenitor cells; JD: Japanese-style diet; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; NAD: nicotinamide adenine dinucleotide; NDUFC2: NADH:ubiquinone oxidoreductase subunit C2; NMN: nicotinamide mononucleotide; RD: regular diet; SHRSP: stroke-prone spontaneously hypertensive rat; SHRSR: stroke-resistant spontaneously hypertensive rat.

Current and emerging avenues for Alzheimer's disease drug targets

Alzheimer's disease (AD), the most frequent cause of dementia, is escalating as a global epidemic, and so far, there is neither cure nor treatment to alter its progression. The most important feature of the disease is neuronal death and loss of cognitive functions, caused probably from several pathological processes in the brain. The main neuropathological features of AD are widely described as amyloid beta (Aβ) plaques and neurofibrillary tangles of the aggregated protein tau, which contribute to the disease. Nevertheless, AD brains suffer from a variety of alterations in function, such as energy metabolism, inflammation and synaptic activity. The latest decades have seen an explosion of genes and molecules that can be employed as targets aiming to improve brain physiology, which can result in preventive strategies for AD. Moreover, therapeutics using these targets can help AD brains to sustain function during the development of AD pathology. Here, we review broadly recent information for potential targets that can modify AD through diverse pharmacological and nonpharmacological approaches including gene therapy. We propose that AD could be tackled not only using combination therapies including Aβ and tau, but also considering insulin and cholesterol metabolism, vascular function, synaptic plasticity, epigenetics, neurovascular junction and blood-brain barrier targets that have been studied recently. We also make a case for the role of gut microbiota in AD. Our hope is to promote the continuing research of diverse targets affecting AD and promote diverse targeting as a near-future strategy.

A differential expression of uncoupling protein-2 associates with renal damage in stroke-resistant spontaneously hypertensive rat/stroke-prone spontaneously hypertensive rat-derived stroke congenic lines

OBJECTIVES

Uncoupling protein-2 (UCP2), a mitochondrial anion transporter involved in mitochondrial uncoupling, limiting reactive oxygen species formation, is significantly downregulated in kidneys of high-salt-fed stroke-prone spontaneously hypertensive rat (SHRSP), where it associates with increased renal damage occurrence.

METHODS

We aimed at establishing whether UCP2 differential expression associates with renal damage in two stroke-resistant spontaneously hypertensive rat (SHRSR)/SHRSP-derived stroke congenic lines. For this purpose, SHRSR, SHRSP, and two reciprocal stroke congenic lines carrying the (D1Rat134-Mt1pa) segment of chromosome 1 were fed with Japanese style diet for 8 weeks. At 4, 6, and 8 weeks of Japanese diet, kidneys were removed and analyzed for UCP2 gene and protein expression [UCP2 maps within (D1Rat134-Mt1pa)]; nuclear factor kappa-light-chain-enhancer of activated B cells protein expression; oxidized total protein levels; mitochondrial function; gene expression of cubulin, megalin, and nephrin. At 6 and 8 weeks of Japanese diet, histological damage and percentage of high molecular weight urinary proteins excretion were assessed.

RESULTS

Introgression of UCP2 in the SHRSP configuration within the SHRSR genome led to UCP2 downregulation upon Japanese diet, as compared with the SHRSR, with significantly reduced ATP levels, increased rate of inflammation, oxidative stress, renal damage, and excretion of high molecular weight proteins. The opposite phenomena were observed in the reciprocal congenic line, compared with the SHRSP. In vitro, high-NaCl medium led to UCP2 downregulation, increased apoptosis/necrosis, and reduced viability in primary renal proximal tubular epithelial cells isolated from SHRSP. Exposure of the SHRSP/proximal tubular epithelial cells to recombinant UCP2 rescued the high-salt-dependent deleterious effects.

CONCLUSION

A differential UCP2 expression associates with different degree of renal damage upon Japanese diet in two SHRSR/SHRSP-derived stroke congenic lines through modulation of mitochondrial function, inflammation, and oxidative stress.

Reduced brain UCP2 expression mediated by microRNA-503 contributes to increased stroke susceptibility in the high-salt fed stroke-prone spontaneously hypertensive rat

UCP2 maps nearby the lod score peak of STR1-stroke QTL in the SHRSP rat strain. We explored the potential contribution of UCP2 to the high-salt diet (JD)-dependent increased stroke susceptibility of SHRSP. Male SHRSP, SHRSR, two reciprocal SHRSR/SHRSP-STR1/QTL stroke congenic lines received JD for 4 weeks to detect brain UCP2 gene/protein modulation as compared with regular diet (RD). Brains were also analyzed for NF-κB protein expression, oxidative stress level and UCP2-targeted microRNAs expression level. Next, based on knowledge that fenofibrate and Brassica Oleracea (BO) stimulate UCP2 expression through PPARα activation, we monitored stroke occurrence in SHRSP receiving JD plus fenofibrate versus vehicle, JD plus BO juice versus BO juice plus PPARα inhibitor. Brain UCP2 expression was markedly reduced by JD in SHRSP and in the (SHRsr.SHRsp-(D1Rat134-Mt1pa)) congenic line, whereas NF-κB expression and oxidative stress level increased. The opposite phenomenon was observed in the SHRSR and in the (SHRsp.SHRsr-(D1Rat134-Mt1pa)) reciprocal congenic line. Interestingly, the UCP2-targeted rno-microRNA-503 was significantly upregulated in SHRSP and decreased in SHRSR upon JD, with consistent changes in the two reciprocal congenic lines. Both fenofibrate and BO significantly decreased brain microRNA-503 level, upregulated UCP2 expression and protected SHRSP from stroke occurrence. In vitro overexpression of microRNA-503 in endothelial cells suppressed UCP2 expression and led to a significant increase of cell mortality with decreased cell viability. Brain UCP2 downregulation is a determinant of increased stroke predisposition in high-salt-fed SHRSP. In this context, UCP2 can be modulated by both pharmacological and nutraceutical agents. The microRNA-503 significantly contributes to mediate brain UCP2 downregulation in JD-fed SHRSP.

Risk of long-term anticoagulation under sustained severe arterial hypertension: A translational study comparing warfarin and the new oral anticoagulant apixaban

New oral anticoagulants for the prevention of stroke and systemic embolism in patients with atrial fibrillation have recently been introduced. In this translational study, we explored the risk of long-term anticoagulation on intracerebral hemorrhage under sustained severe arterial hypertension. We initiated anticoagulation with warfarin or apixaban in spontaneously hypertensive rats prone to develop severe hypertension and subsequent intracerebral bleeding complications. A non-anticoagulated group served as control. During an 11-week-study period, blood pressure, anticoagulation parameters, and clinical status were determined regularly. The incidence of histopathologically proven intracerebral hemorrhage was defined as the primary endpoint. Both warfarin and apixaban anticoagulation was fairly stable during the study period, and all rats developed severe hypertension. Intracerebral hemorrhage was determined in 29% (4/14) of warfarin rats and in 10% (1/10) of apixaban rats. Controls did not show cerebral bleeding complications (chi-square not significant). Mortality rate at study termination was 33% (2/6) in controls, 43% (6/14) in the warfarin group, and 60% (6/10) in the apixaban group. Animals died from extracerebral complications in most cases. Our study describes an experimental intracerebral hemorrhage model in the context of sustained hypertension and long-term anticoagulation. Extracerebral bleeding complications occurred more often in warfarin-treated animals compared with apixaban and control rats.

Mitochondrial Dysfunction Contributes to Hypertensive Target Organ Damage: Lessons from an Animal Model of Human Disease

Mechanisms underlying hypertensive target organ damage (TOD) are not completely understood. The pathophysiological role of mitochondrial oxidative stress, resulting from mitochondrial dysfunction, in development of TOD is unclear. The stroke-prone spontaneously hypertensive rat (SHRSP) is a suitable model of human hypertension and of its vascular consequences. Pathogenesis of TOD in SHRSP is multifactorial, being determined by high blood pressure levels, high salt/low potassium diet, and genetic factors. Accumulating evidence points to a key role of mitochondrial dysfunction in increased susceptibility to TOD development of SHRSP. Mitochondrial abnormalities were described in both heart and brain of SHRSP. Pharmacological compounds able to protect mitochondrial function exerted a significant protective effect on TOD development, independently of blood pressure levels. Through our research efforts, we discovered that two genes encoding mitochondrial proteins, one (Ndufc2) involved in OXPHOS complex I assembly and activity and the second one (UCP2) involved in clearance of mitochondrial ROS, are responsible, when dysregulated, for vascular damage in SHRSP. The suitability of SHRSP as a model of human disease represents a promising background for future translation of the experimental findings to human hypertension. Novel therapeutic strategies toward mitochondrial molecular targets may become a valuable tool for prevention and treatment of TOD in human hypertension.

Common Impact of Chronic Kidney Disease and Brain Microhemorrhages on Cerebral Aβ Pathology in SHRSP

While chronic kidney disease seems to be an independent risk factor for cognitive decline, its impact on cerebral amyloid-β (Aβ) depositions, one hallmark of Alzheimer's Disease (AD) pathology, has not been investigated. Utilizing 80 male nontransgenic spontaneously hypertensive stroke prone rats (SHRSP) at various ages (12 to 44 weeks), tubulointerstitial renal damage, prevalence of cerebral microhemorrhages and Aβ accumulations were quantified. Using age-adjusted general linear models we investigated the main and interaction effects of renal damage and cerebral microhemorrhages on cerebral Aβ load. In addition, using post mortem human brain tissue of 16 stroke patients we examined the co-localization of perivascular Aβ deposits and small vessel wall damage. Statistical models revealed an age-independent main effect of tubulointerstitial kidney damage on brain Aβ accumulations, which was reinforced by the consecutive presence of cerebral microhemorrhages. Moreover, cerebral microhemorrhages independently predicted brain Aβ burden in SHRSP. In up to 69% of all human cases perivascular Aβ deposits were detected in the direct vicinity of small vessel wall damage. Our results support the associations between vascular pathology and Aβ deposition, and demonstrate a relationship between chronic kidney disease and cerebral Aβ pathology. Hence, our data suggest that prevention of chronic renal damage may reduce cerebral Aβ pathology.

Ndufc2 Gene Inhibition Is Associated With Mitochondrial Dysfunction and Increased Stroke Susceptibility in an Animal Model of Complex Human Disease

BACKGROUND

The genetic basis of stroke susceptibility remains to be elucidated. STR1 quantitative trait locus (STR1/QTL) was identified on rat chromosome 1 of stroke-prone spontaneously hypertensive rat (SHRSP) upon Japanese-style stroke-permissive diet (JD), and it contributes to 20% of the stroke phenotype variance.

METHODS AND RESULTS

Nine hundred eighty-six probe sets mapping on STR1 were selected from the Rat RAE230A array and screened through a microarray differential expression analysis in brains of SHRSP and stroke-resistant SHR (SHRSR) fed with either regular diet or JD. The gene encoding Ndufc2 (NADH dehydrogenase [ubiquinone] 1 subunit), mapping 8 Mb apart from STR1/QTL Lod score peak, was found significantly down-regulated under JD in SHRSP compared to SHRSR. Ndufc2 disruption altered complex I assembly and activity, reduced mitochondrial membrane potential and ATP levels, and increased reactive oxygen species production and inflammation both in vitro and in vivo. SHRSR carrying heterozygous Ndufc2 deletion showed renal abnormalities and stroke occurrence under JD, similarly to SHRSP. In humans, T allele variant at NDUFC2/rs11237379 was associated with significant reduction in gene expression and with increased occurrence of early-onset ischemic stroke by recessive mode of transmission (odds ratio [OR], 1.39; CI, 1.07-1.80; P=0.012). Subjects carrying TT/rs11237379 and A allele variant at NDUFC2/rs641836 had further increased risk of stroke (OR=1.56; CI, 1.14-2.13; P=0.006).

CONCLUSIONS

A significant reduction of Ndufc2 expression causes complex I dysfunction and contributes to stroke susceptibility in SHRSP. Moreover, our current evidence may suggest that Ndufc2 can contribute to an increased occurrence of early-onset ischemic stroke in humans.

Differential modulation of AMPK/PPARα/UCP2 axis in relation to hypertension and aging in the brain, kidneys and heart of two closely related spontaneously hypertensive rat strains

OBJECTIVES

We examined expression protein of AMPK/SIRT1/PGC1α/PhoxO3a/PPARα/UCP2 pathway in brain, kidneys and heart of stroke-prone spontaneously hypertensive rat (SHRSP) vs stroke-resistant SHR (SHRSR) at different weeks of age, up to one year, in order to test the hypothesis that abnormalities within this pathway could associate with higher susceptibility of SHRSP to develop hypertension-related vascular damage.

BACKGROUND

SHRSP develops severe hypertension and related target organ damage. Marked reduction of uncoupling protein 2 (UCP2) expression upon high salt-low potassium diet associates with increased renal injury in SHRSP. UCP2 may represent a key mitochondrial protein involved in cardiovascular damage.

RESULTS

At 2 months of age a significant down-regulation of UCP2 expression at both mRNA and protein levels was found, along with reduced protein expression of all components of UCP2 regulatory pathway, in tissues of SHRSP but not of SHRSR, that progressed with hypertension development and aging. A significant increase of both oxidative stress and inflammation was detected in tissues of SHRSP as a function of age. SBP levels were significantly higher in SHRSP than SHRSR at 3 months of age and thereafter. At one year of age, higher degree of renal damage, with proteinuria and severe glomerular and tubulo-interstitial fibrosis, of cerebral damage, with significant vessel extravasation and stroke occurrence, and of myocardial damage was detected in SHRSP than SHRSR. 

CONCLUSIONS

The early significant reduced expression of the antioxidant AMPK/PPARα/UCP2 pathway that progressed throughout lifetime may contribute to explain higher predisposition of SHRSP to oxidative stress dependent target organ damage in the context of severe hypertension.

Spontaneous white matter damage, cognitive decline and neuroinflammation in middle-aged hypertensive rats: an animal model of early-stage cerebral small vessel disease

Introduction

Cerebral small vessel disease (cSVD) is one of the most prevalent neurological disorders. The progressive remodeling of brain microvessels due to arterial hypertension or other vascular risk factors causes subtle, but constant cognitive decline through to manifest dementia and substantially increases the risk for stroke. Preliminary evidence suggests the contribution of the immune system to disease initiation and progression, but a more detailed understanding is impaired by the unavailability of appropriate animal models. Here, we introduce the spontaneously hypertensive rat (SHR) as a model for early onset cSVD and unveiled substantial immune changes in conjunction with brain abnormalities that resemble clinical findings.

Results

In contrast to age-matched normotensive Wistar Kyoto (WKY) rats, male SHR exhibited non-spatial memory deficits. Magnetic resonance imaging showed brain atrophy and a reduction of white matter volumes in SHR. Histological analyses confirmed white matter demyelination and unveiled a circumscribed blood brain barrier dysfunction in conjunction with micro- and macrogliosis in deep cortical regions. Flow cytometry and histological analyses further revealed substantial disparities in cerebral CD45high leukocyte counts and distribution patterns between SHR and WKY. SHR showed lower counts of T cells in the choroid plexus and meningeal spaces as well as decreased interleukin-10 levels in the cerebrospinal fluid. On the other hand, both T and NK cells were significantly augmented in the SHR brain microvasculature.

Conclusions

Our results indicate that SHR share behavioral and neuropathological characteristics with human cSVD patients and further undergird the relevance of immune responses for the initiation and progression of cSVD.

Electronic supplementary material

The online version of this article (doi:10.1186/s40478-014-0169-8) contains supplementary material, which is available to authorized users.

Blood brain barrier breakdown as the starting point of cerebral small vessel disease? - New insights from a rat model

Cerebral small vessel disease (CSVD, cerebral microangiopathy) leads to dementia and stroke-like symptoms. Lacunes, white matter lesions (WML) and microbleeds are the main pathological correlates depicted in in-vivo imaging diagnostics. Early studies described segmental arterial wall disorganizations of small penetrating cerebral arteries as the most pronounced underlying histopathology of lacunes. Luminal narrowing caused by arteriolosclerosis was supposed to result in hypoperfusion with WML and infarcts.We have used the model of spontaneously hypertensive stroke-prone rats (SHRSP) for a longitudinal study to elucidate early histological changes in small cerebral vessels. We suggest that endothelial injuries lead to multiple sites with blood brain barrier (BBB) leakage which cause an ongoing damage of the vessel wall and finally resulting in vessel ruptures and microbleeds. These microbleeds together with reactive small vessel occlusions induce overt cystic infarcts of the surrounding parenchyma. Thus, multiple endothelial leakage sites seem to be the starting point of cerebral microangiopathy. The vascular system reacts with an activated coagulatory state to these early endothelial injuries and by this induces the formation of stases, accumulations of erythrocytes, which represent the earliest detectable histological peculiarity of small vessel disease in SHRSP.In this review we focus on the meaning of the BBB breakdown in CSVD and finally discuss possible consequences for clinicians.

Differential modulation of uncoupling protein 2 in kidneys of stroke-prone spontaneously hypertensive rats under high-salt/low-potassium diet

The stroke-prone spontaneously hypertensive rat (SHRsp) represents an animal model of increased susceptibility to high-salt diet-induced cerebral and renal vascular injuries. High blood pressure and genetic factors are viewed as major contributing factors. In high-salt-loaded SHRsp and stroke-resistant SHR animals, we determined blood pressure levels, degree of kidney lesions, renal uncoupling protein 2 (UCP2) gene and protein expression levels along with rattus norvegicus (rno)-microRNA (miR) 24 and 34a gene expression, nuclear factor-κB protein levels, and oxidative stress. In vitro, UCP2 gene silencing was performed in renal mesangial cells. We found more severe degree of renal damage in SHRsp at the end of 4-week high-salt dietary treatment as compared with stroke-resistant SHR, despite comparable blood pressure levels, along with increased rate of inflammation and oxidative stress. Kidney UCP2 gene and protein expression levels were significantly downregulated under high-salt diet in SHRsp, but not in stroke-resistant SHR. Differential UCP2 regulation was paralleled by differential expression of kidney rno-miR 24 and 34a, known to target UCP2 gene, in the 2 strains. UCP2 gene silencing in renal mesangial cells led to increased rate of reactive oxygen species generation, increased inflammation and apoptosis, reduced cell vitality, and increased necrosis. In conclusion, high-salt diet downregulates the antioxidant UCP2-dependent mechanism in kidneys of SHRsp, but not of stroke-resistant SHR. A parallel differential kidney miR regulation under high-salt diet in the 2 strains may contribute to the differential UCP2 modulation. UCP2 is a critical protein to prevent oxidative stress damage in renal mesangial cells in vitro.

Do basophile structures as age dependent phenomenon indicate small vessel wall damage?

Here we demonstrate basophile structures located in the arteriolar wall and being associated with a plasma-protein-leakage. We assume, that the structures indicate blood-brain-barrier-disturbances and degenerative small vessel wall alterations.

Stases are associated with blood-brain barrier damage and a restricted activation of coagulation in SHRSP

Cerebral small vessel disease (CSVD) is a chronically proceeding pathology of small brain vessels associated with white matter lesions, lacunar infarcts, brain atrophy and microbleeds. CSVD leads to slowly increasing cognitive and functional deficits but may also cause stroke-like symptoms, if vessels in critical brain areas are affected. Spontaneously hypertensive stroke-prone rats (SHRSP) exhibit several vascular risk factors, develop infarcts and hemorrhages and therefore represent a relevant model for the study of CSVD. Using this animal model, we recently demonstrated that intravasal accumulations of erythrocytes, we interpreted as stases, stand at the beginning of a pathological vascular cascade. After stases microbleeds occur, which are followed by reactive microthromboses. Bleeds and thromboses finally cause hemorrhagic infarcts. Immunohistochemical stainings show, that plasma proteins like IgG are deposited in the walls of vessels affected by stases. Further, we found small clots and thread-shaped aggregations of thrombocytes as well as thread-shaped structures of von Willebrand-Factor within stases. Thus, we conclude that blood-brain barrier damages occur in the neighborhood of stases and stases seem to be associated with a restricted activation of blood coagulation without formation of obstructive thromboses. Finally, we demonstrate that small vessel damage rarely appears in the cerebellum. Even animals with multiple cerebral infarcts may be free of any cerebellar vascular pathology.