Renal involvement in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL)

Deletion of Notch3 Impairs Contractility of Renal Resistance Vessels Due to Deficient Ca2+ Entry

Notch3 plays an important role in the differentiation and development of vascular smooth muscle cells. Mice lacking Notch3 show deficient renal autoregulation. The aim of the study was to investigate the mechanisms involved in the Notch3-mediated control of renal vascular response. To this end, renal resistance vessels (afferent arterioles) were isolated from Notch3^-/- and wild-type littermates (WT) and stimulated with angiotensin II (ANG II). Contractions and intracellular Ca²⁺ concentrations were blunted in Notch3^-/- vessels. ANG II responses in precapillary muscle arterioles were similar between the WT and Notch3^-/- mice, suggesting a focal action of Notch3 in renal vasculature. Abolishing stored Ca²⁺ with thapsigargin reduced Ca²⁺ responses in the renal vessels of the two strains, signifying intact intracellular Ca²⁺ mobilization in Notch3^-/-. EGTA (Ca²⁺ chelating agent), nifedipine (L-type channel-blocker), or mibefradil (T-type channel-blocker) strongly reduced contraction and Ca²⁺ responses in WT mice but had no effect in Notch3^-/- mice, indicating defective Ca²⁺ entry. Notch3^-/- vessels responded normally to KCl-induced depolarization, which activates L-type channels directly. Differential transcriptomic analysis showed a major down-regulation of Cacna1h gene expression, coding for the α_1H subunit of the T-type Ca²⁺ channel, in Notch3^-/- vessels. In conclusion, renal resistance vessels from Notch3^-/- mice display altered vascular reactivity to ANG II due to deficient Ca²⁺-entry. Consequently, Notch3 is essential for proper excitation-contraction coupling and vascular-tone regulation in the kidney.

The pericyte: A critical cell in the pathogenesis of CADASIL

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CADASIL is the most common hereditary small vessel disease presenting with strokes and subcortical vascular dementia caused by mutations in the NOTCH3 gene.

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CADASIL is a vasculopathy primarily involving vascular smooth-muscle cells.

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Arteriolar and capillary pericyte damage or deficiency is a key feature in disease pathogenesis.

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Pericyte-mediated cerebral venous insufficiency may explain white matter lesions and increased perivascular spaces.

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Central role of the pericyte offers novel approaches to the treatment of CADASIL.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary small vessel disease presenting with migraine, mood and cognitive disorders, focal neurological deficits, recurrent ischemic attacks, lacunar infarcts and brain white matter changes. As they age, CADASIL patients invariably develop cognitive impairment and subcortical dementia. CADASIL is caused by missense mutations in the NOTCH3 gene resulting in a profound cerebral vasculopathy affecting primarily arterial vascular smooth muscle cells, which target the microcirculation and perfusion. Based on a thorough review of morphological lesions in arteries, veins, and capillaries in CADASIL, we surmise that arteriolar and capillary pericyte damage or deficiency appears a key feature in the pathogenesis of the disease. This may affect critical pericyte-endothelial interactions causing stroke injury and vasomotor disturbances. Changes in microvascular permeability due to perhaps localized blood-brain barrier alterations and pericyte secretory dysfunction likely contribute to delayed neuronal as well as glial cell death. Moreover, pericyte-mediated cerebral venous insufficiency may explain white matter lesions and the dilatation of Virchow-Robin perivascular spaces typical of CADASIL. The postulated central role of the pericyte offers some novel approaches to the study and treatment of CADASIL and enable elucidation of other forms of cerebral small vessel diseases and subcortical vascular dementia.

Peripheral arteriopathy caused by Notch3 gain-of-function mutation involves ER and oxidative stress and blunting of NO/sGC/cGMP pathway

Notch3 mutations cause Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL), which predisposes to stroke and dementia. CADASIL is characterised by vascular dysfunction and granular osmiophilic material (GOM) accumulation in cerebral small vessels. Systemic vessels may also be impacted by Notch3 mutations. However vascular characteristics and pathophysiological processes remain elusive. We investigated mechanisms underlying the peripheral vasculopathy mediated by CADASIL-causing Notch3 gain-of-function mutation. We studied: (i) small arteries and vascular smooth muscle cells (VSMCs) from TgNotch3R169C mice (CADASIL model), (ii) VSMCs from peripheral arteries from CADASIL patients, and (iii) post-mortem brains from CADASIL individuals. TgNotch3R169C vessels exhibited GOM deposits, increased vasoreactivity and impaired vasorelaxation. Hypercontractile responses were normalised by fasudil (Rho kinase inhibitor) and 4-phenylbutyrate (4-PBA; endoplasmic-reticulum (ER) stress inhibitor). Ca2+ transients and Ca2+ channel expression were increased in CADASIL VSMCs, with increased expression of Rho guanine nucleotide-exchange factors (GEFs) and ER stress proteins. Vasorelaxation mechanisms were impaired in CADASIL, evidenced by decreased endothelial nitric oxide synthase (eNOS) phosphorylation and reduced cyclic guanosine 3',5'-monophosphate (cGMP) levels, with associated increased soluble guanylate cyclase (sGC) oxidation, decreased sGC activity and reduced levels of the vasodilator hydrogen peroxide (H2O2). In VSMCs from CADASIL patients, sGC oxidation was increased and cGMP levels decreased, effects normalised by fasudil and 4-PBA. Cerebral vessels in CADASIL patients exhibited significant oxidative damage. In conclusion, peripheral vascular dysfunction in CADASIL is associated with altered Ca2+ homoeostasis, oxidative stress and blunted eNOS/sGC/cGMP signaling, processes involving Rho kinase and ER stress. We identify novel pathways underlying the peripheral arteriopathy induced by Notch3 gain-of-function mutation, phenomena that may also be important in cerebral vessels.

Clinical and Genetic Aspects of CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a hereditary cerebral small vessel disease caused by mutations in NOTCH3, is characterized by recurrent stroke without vascular risk factors, mood disturbances, and dementia. MRI imaging shows cerebral white matter (WM) hyperintensity, particularly in the external capsule and temporal pole. Missense mutations related to a cysteine residue in the 34 EGFr on the NOTCH3 extracellular domain (N3ECD) are a typical mutation of CADASIL. On the other hand, atypical mutations including cysteine sparing mutation, null mutation, homozygous mutation, and other associate genes are also reported. From the viewpoint of gain of function apart from Notch signaling or loss of function of Notch signaling, we review the research article about CADASIL and summarized the pathogenesis of small vessel, stroke, and dementia in this disease.

Notch Signaling in Kidney Development, Maintenance, and Disease

Kidney development involves formation of nephrons intricately aligned with the vasculature and connected to a branched network of collecting ducts. Notch signaling plays multiple roles during kidney development involving the formation of nephrons composed of diverse epithelial cell types arranged into tubular segments, all the while maintaining a nephron progenitor niche. Here, we review the roles of Notch signaling identified from rodent kidney development and injury studies, while discussing human kidney diseases associated with aberrant Notch signaling. We also review Notch signaling requirement in maintenance of mature kidney epithelial cell states and speculate that Notch activity regulation mediates certain renal physiologic adaptations.

A CADASIL-Like Case with a Novel Noncysteine Mutation of the NOTCH3 Gene and Granular Deposits in the Renal Arterioles

We herein report the finding of a 62-year-old male, who developed dysarthria and dysphagia, with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy- (CADASIL-) like cerebral lesions. He also suffered from slowly progressive renal failure with the findings of granular deposits similar to electron-dense granular osmiophilic material in the renal arterioles. We found a novel heterozygous missense mutation of the NOTCH3 gene, c.4039G>C in exon 24, resulting in a p.Gly1347Arg substitution in its extracellular domain. The noncysteine substitution may underlie the pathogenesis of white matter lesions in the brain and of the chronic renal failure in the present case.

Role of electron microscopy in the diagnosis of cadasil syndrome: a study of 32 patients

Background and Purpose

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is caused by NOTCH3 gene mutations that result in vascular smooth muscle cell (VSMC) degeneration. Its distinctive feature by electron microscopy (EM) is granular osmiophilic material (GOM) detected in VSMC indentations and/or the extracellular space close to VSMCs. Reports of the sensitivity of EM in detecting GOM in biopsies from CADASIL patients are contradictory. We present data from 32 patients clinically suspected to have CADASIL and discuss the role of EM in its diagnosis in this retrospective study.

Methods

Skin, skeletal muscle, kidney and pericardial biopsies were examined by EM; the NOTCH3 gene was screened for mutations. Skin and muscle biopsies from 12 patients without neurological symptoms served as controls.

Results and Discussion

All GOM-positive patients exhibited NOTCH3 mutations and vice versa. This study i) confirms that EM is highly specific and sensitive for CADASIL diagnosis; ii) extends our knowledge of GOM distribution in tissues where it has never been described, e.g. pericardium; iii) documents a novel NOTCH3 mutation in exon 3; and iv) shows that EM analysis is critical to highlight the need for comprehensive NOTCH3 analysis. Our findings also confirm the genetic heterogeneity of CADASIL in a small Italian subpopulation and emphasize the difficulties in designing algorithms for molecular diagnosis.

Notch3 and kidney injury: never two without three

Notch receptors and their canonical ligands are transmembrane proteins of the EGF-like family, expressed in the cell surface. Notch receptors are synthesized as single peptides and undergo three sequential proteolytic cleavage steps before rendering an active transcription factor, the Notch intracellular domain (NICD). Ligand binding facilitates release of NICD by γ-secretase. Evidence for the role of the Notch pathway in kidney injury comes from studies on activation of Notch by canonical ligands in cultured cells, on inhibition/targeting of γ-secretase in culture or in vivo, on genetic deletion of common Notch pathway proteins such as CSL, or descriptions of increased transcription of Notch target genes in kidney injury. Inhibitors of γ-secretase prevent fibrosis in experimental kidney injury. However, these drugs may modulate other signalling systems beyond Notch and are toxic in human trials. Information regarding the specific contribution of each receptor to kidney injury may help design better targeted therapeutic approaches. In this regard, overexpression of NICD1, NCID2, NICD3 or NICD4 elicits biological responses in cultured renal cells that include cell proliferation, apoptosis, and inflammatory and profibrotic responses, depending on the particular NICD. Furthermore, immunostaining for NICD1, NICD2, and NICD4 suggestive of receptor activation has been observed in glomerular and tubular cells in human and experimental kidney disease. Delayed conditional Notch1 or Notch2 inactivation facilitates cyst formation, and NICD1 overexpression in podocytes or tubular cells promotes glomerulosclerosis and interstitial fibrosis. Kidney injury is a feature of human Notch2 mutations and CADASIL patients with mutated Notch3 may display renal injury. Notch3-/- mice display increased sensitivity to angiotensin II-induced kidney injury but are less sensitive to tubular injury, inflammation, and fibrosis following unilateral ureteral obstruction. The recent availability of blocking antibodies specific for Notch1, Notch2, and Notch3 may help to elucidate the therapeutic potential of specific targeting of individual Notch receptors in kidney disease.

Is the SHRSP [corrected] strain a suitable model of spontaneous CADASIL?

A number of features of the pathology occurring in spontaneously hypertensive stroke prone rats (SHRSPs), such as MRI brain signal abnormalities, the presence of high protein content in cerebrospinal fluid and vessel wall thickening, seem to indicate that this strain is a suitable model for cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). To explore this hypothesis, we sought the human diagnostic hallmarks of the disease [the accumulation of granular osmiophilic material (GOM) deposits in vessel walls and NOTCH3 gene mutations] in SHRSPs. Male SHRSPs fed a permissive diet were sacrificed 3 days after the first MRI visualisation of brain abnormalities. Whole blood and kidney samples were respectively collected for molecular and electron microscopy evaluations. Automated sequence analysis of exons and intron-exon boundaries did not reveal any genetic variation in the NOTCH3 gene, and electron microscopy excluded the presence of GOM. The findings of this study exclude SHRSPs as a possible model for CADASIL.

Notch3 is essential for regulation of the renal vascular tone

The Notch3 receptor participates in the development and maturation of vessels. Mutations of Notch3 in humans are associated with defective regulation of cerebral blood flow. To investigate the role of Notch3 in the regulation of renal hemodynamics, we used mice lacking expression of the Notch3 gene (Notch3-/- mice). Bolus injections of norepinephrine and angiotensin II increased renal vascular resistance and decreased renal blood flow in a dose-dependent manner in wild-type mice. In sharp contrast, renal vascular resistance of Notch3-/- mice varied little after boluses of norepinephrine and angiotensin II. Inversely, bradykinin and prostacyclin relaxed renal vasculature in wild-type mice. Both vasodilators had a negligible effect on renal vascular resistance of Notch3-/- mice. Afferent arterioles freshly isolated from Notch3-/- mice displayed decreased thickness of vascular wall compared with wild -type mice and showed a deficient contractile response to angiotensin II. To examine the physiopathological consequences of the above-described deficiency, hypertension was induced by continuous infusion of angiotensin II. Angiotensin II gradually increased blood pressure in both strains, but this increase was lesser in the Notch3-/- mice. Despite this blunted systemic effect, Notch3-/- mice displayed high mortality rates (65%) attributed to heart failure. In the kidney, the surviving Notch3-/- mice showed focal structural alterations characteristic of nephroangiosclerosis. These data show that Notch3 is necessary for the adaptive response of the renal vasculature to vasoactive systems. A deficiency in the expression of Notch3 could have important physiopathological consequences in the adaptation of the cardiac and renal function to chronic increase of blood pressure.

CADASIL: pathogenesis, clinical and radiological findings and treatment

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is the most common genetic cause of ischemic strokes and a most important model for the study of subcortical vascular dementia. This unrelentlessly progressive disease affects many hundreds of families all over the world but is not well studied in Brazil. This manuscript reviews pathogenetic, clinical, radiological and therapeutic features of CADASIL. The causal mutations are now very well known, but the same can not be said about its intimate pathogenetic mechanisms. The variable clinical presentation should lead physicians to actively pursue the diagnosis in many settings and to more thouroughly investigate family history in first degree relatives. A rational approach to genetic testing is however needed. Treatment of CADASIL is still largely empiric. High-quality therapeutic studies involving medications and cognitive interventions are strongly needed in CADASIL.

YB-1 acts as a ligand for Notch-3 receptors and modulates receptor activation

Y-box (YB) protein-1 is secreted by mesangial and immune cells after cytokine challenge, but extracellular functions are unknown. Here, we demonstrate that extracellular YB-1 associates with outer cell membrane components and interacts with extracellular Notch-3 receptor domains. The interaction appears to be specific for Notch-3, as YB-1-green fluorescent protein binds to the extracellular domains and full-length forms of Notch-3 but not to Notch-1. YB-1-green fluorescent protein and Notch-3 proteins co-localize at cell membranes, and extracellular YB-1 activates Notch-3 signaling, resulting in nuclear translocation of the Notch-3 intracellular domain and up-regulation of Notch target genes. The YB-1/Notch-3 interaction may be of particular relevance for inflammatory mesangioproliferative disease, as both proteins co-localize in an experimental nephritis model and receptor activation temporally and spatially correlates with YB-1 expression.

Nephroangiosclerosis in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy: is NOTCH3 mutation the common culprit?

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a systemic arterial disease characterized by impairment of vascular smooth muscle cell structure and function related to NOTCH3 mutations. Pathological findings include pathognomonic granular osmiophilic material (GOM) deposition with nonspecific hyalinization within the artery wall in a variety of tissues. The main clinical presentation is iterative strokes in young adults despite the lack of cardiovascular risk factors, leading to early dementia. Although arteriosclerosis and GOM have been found in kidneys from patients with CADASIL, kidney disease has been described only once up to now, in association with immunoglobulin A nephropathy. We report the case of a 61-year-old patient with a medical history of CADASIL and recent mild hypertension. His mother also showed neuropsychiatric symptoms and end-stage renal disease of unknown cause. The patient had a chronic kidney disease defined by means of estimated glomerular filtration rate using the 4-variable Modification of Diet in Renal Disease Study equation of 58 mL/min/1.73 m(2) associated with mild proteinuria and intermittent microscopic hematuria. Renal histological analysis showed severe arteriosclerosis and mild interstitial fibrosis. Glomeruli did not show mesangial immunoglobulin A deposition or focal segmental proliferation. Electron microscopic analysis showed typical GOM deposition in the vicinity of altered vascular smooth muscle cells in interlobular and juxtaglomerular arteries. The nephroangiosclerosis-like lesions were unusually severe in contrast to the recent mild hypertension. The presence of GOM strongly suggests that renal lesions were related to the NOTCH3 mutation. Here, we describe the first case of familial occurrence of kidney disease with decreased kidney function in the absence of coexisting nephropathy in patients with CADASIL. We discuss the role of NOTCH3 mutation in the pathogenesis of nephroangiosclerosis through functional impairment of renal microcirculation or primary Notch3-related vascular disease.