The ubiquitin-proteasome system in kidney physiology and disease.

Intracellular proteins continuously turn over by degradation and synthesis in all organ tissues. Owing to its irreversible nature, protein degradation is a highly selective process to avoid irreparable breakdown of cellular constituents, thereby disrupting cellular stability, integrity and signalling. The majority of intracellular proteins are degraded by the ubiquitin-proteasome system (UPS), a multi-enzyme process that involves the covalent conjugation of ubiquitin to a substrate protein and its recognition and degradation by the core multicomponent proteolytic complex of the UPS, the proteasome. In addition to labelling misfolded, damaged, aggregation-prone and intact but unneeded proteins for proteasomal degradation, ubiquitylation regulates a multitude of cellular processes, such as transcription, translation, endocytosis, and receptor activity and subcellular localization. In addition, the proteasome generates peptides for antigen presentation in the immune system and for further degradation by peptidases to provide amino acids for protein biosynthesis and gluconeogenesis. Alterations of the UPS or of protein substrates that render them more or less susceptible to degradation are responsible for disorders associated with renal cell dysfunction. In this Review, we provide insight into the elegant and complex nature of UPS-mediated proteostasis and focus on its established and potential roles in renal cell physiology and pathophysiology.

Pathophysiology and management of glaucoma associated with phakomatoses.

The phakomatoses, encephalotrigeminal angiomatosis (ETA; Sturge-Weber Syndrome), neurofibromatosis type 1 (NF1 or von Recklinghausen disease), Von Hippel-Lindau (VHL) disease, tuberous sclerosis (TSC), oculodermal melanocytosis (ODM), and phakomatosis pigmentovascularis are a group of neurocutaneous disorders that have characteristic systemic and ocular manifestations. Through many different mechanisms, they may cause glaucomatous damage of the optic nerve and subsequent vision loss varying from mild to severe. Glaucoma commonly affects patients with ETA (43-72%), orbito-facial NF1 (23-50%), and ODM (10%). Rarely, it may present as neovascular glaucoma in VHL and TSC. In ETA, glaucoma typically occurs ipsilateral to the port-wine stain, which is caused by a mutation in the GNAQ gene. Specifically, mechanical malformation of the anterior chamber angle and elevated episcleral venous pressure has been implicated as causes of glaucoma in ETA. In NF1, which is caused by a mutation in the NF1 tumor suppressor gene, glaucoma commonly occurs ipsilateral to lid plexiform neurofibromas. Histological studies of eyes with NF1 have revealed direct anterior chamber infiltration by neurofibromas, secondary angle closure, fibrovascularization, and developmental angle abnormalities as mechanisms of glaucoma. Lastly, phakomatosis pigmentovascularis is a rare combination of ODM and port-wine stain. Affected patients are at very high risk of developing glaucoma. Despite the many different mechanisms of glaucomatous damage, management follows similar principles as that for congenital glaucoma and primary open angle glaucoma. First-line therapy is topical intraocular pressure-lowering eye drops. Surgical management, including goniotomy, trabeculotomy, trabeculectomy, and tube shunt placement may be required for more severe cases.

Von Hippel-Lindau Disease.

Phakomatoses (phakoma = birthmark) are a group of diseases or syndromes that have hamartomas (tumorous malformations composed of tissues normally present at the location where they develop) of the skin, brain, and eye (oculoneurocutaneous syndromes).

An Advanced Well-differentiated Pancreatic Neuroendocrine Carcinoma (NET-G3) Associated with Von Hippel-Lindau Disease.

A 45-year old woman who underwent several surgeries for tumors associated with von Hippel-Lindau disease (VHL) was referred to our hospital due to a pancreatic tumor and liver tumors. She was diagnosed with pancreatic neuroendocrine tumor (NET) with a Ki67 index of 40% based on the examination of a biopsy specimen of the liver tumors. She was treated with everolimus for 6 months and sunitinib for 6 weeks as first- and second-line therapies. She survived for 13 months. At autopsy the diagnosis of pancreatic neuroendocrine tumor (NET)-G3 was confirmed. We herein report an aggressive clinical course of VHL-related NET G3. The further accumulation of cases is required to reach a consensus on treatment for this disease.

Múltiples imágenes nodulares hipervasculares / Multiple hypervascular nodule images

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von Hippel-Lindau development in children and adolescents.

The autosomal dominant von Hippel-Lindau disease (vHL) is associated with a lifelong risk of tumor development, especially retinal and CNS hemangioblastomas, pheochromocytoma, and renal cell carcinoma. Knowledge of paediatric vHL development is limited, and current surveillance guidelines are based on expert opinions. We aimed to describe the course of vHL development in children and adolescents, focusing on age at first manifestation, manifestation frequencies, and types. The prevalence of vHL diagnosis as well as manifestations in childhood were evaluated based on 99 patients, who had started surveillance before 18 years: 37 Danish patients from the national vHL research database and 62 international patients reported in 15 articles. Overall, 70% (69 of 99) developed manifestations before 18 years (median age at first manifestation: 12 years (range: 6-17 years)). Thirty per cent (30 of 99) had developed more than one manifestation type; the most frequent were retinal (34%) and CNS (30%) hemangioblastomas. Among the 37 Danish patients, 85% (97 of 116) of their tumors were asymptomatic. Vision outcome is significantly improved in hemangioblastomas that are treated while still asymptomatic. We agree with current guidelines that retinal surveillance be performed from birth. The patients had their first CNS hemangioblastomas at the median ages of 13-14 years (range: 6-17 years). Further, 11% (4 of 37) of the Danish patients had CNS surgery in their teenage years. Although the cohort is too small to make definite conclusions about specific initiation ages, regular CNS surveillance from vHL patients' teenage years seems clinically relevant.

Von Hippel-Lindau disease involving pancreas and biliary system: A rare case report.

RATIONALE: Von Hippel-Lindau (VHL) disease is a rare inherited, autosomal-dominant syndrome caused by heterozygous germline mutations in the VHL gene. VHL patients are prone to develop benign and malignant tumors and cysts in multiple organ systems involving kidneys, pancreas and central nervous system (CNS). The varied and complex clinical manifestations and radiological findings of VHL are of interest. PATIENT CONCERNS: We report a 38-year-old woman with a ten-year history of VHL disease involving both pancreas and biliary system. To the best of our knowledge, direct involvement of the biliary system in VHL disease has never been reported. DIAGNOSES: The diagnosis was established via computed tomography scan and was confirmed by genetic testing. INTERVENTIONS: The patient chose to receive conservative treatment and was followed up by magnetic resonance cholangiopancreatography and magnetic resonance imaging examination. OUTCOMES: Renal angiomas and cysts were found during follow-up and there were no evidence of malignant change of the pancreas and biliary system. LESSONS: We described the first case of VHL-associated choledochal cysts and may present new visceral manifestations of VHL disease. Gastroenterologists should be aware of the clinical presentations of this rare disease for early detection of its life-threatening manifestations.

Terson's Syndrome in a Patient with von Hippel-Lindau Disease.

PURPOSE: Terson's syndrome is a condition where a preretinal hemorrhage forms as a result of increased intracranial pressure. The elevated intracranial pressure is thought to be transmitted through the veins and the optic nerve sheath to the optic disc and retina, causing the thin capillary walls to rupture. The authors present a unique case of Terson's syndrome in a patient who underwent recent surgical management for cerebellar hemangioblastomas related to von Hippel-Lindau disease. CASE REPORT: A 17-year-old African American female patient with a history of von Hippel-Lindau disease presented with pain in her right eye. She had recently undergone surgery to remove cerebellar hemangioblastomas. Preliminary fundus imaging was performed, but before formal ophthalmic testing could be conducted, the patient seized and was taken directly to the emergency room. When the patient returned for a formal evaluation 3 weeks later, a new preretinal "boat-shaped" hemorrhage was now present. Additionally, reports from the emergency room suggested that she had bled into the cavity where the previous cerebellar resection had taken place. This hemorrhage likely led to an increase in intracranial pressure, causing a Terson's-like event. CONCLUSIONS: A Terson's event may be caused by high intracranial pressure secondary to the surgical removal of von Hippel-Lindau syndrome-associated cerebellar tumors and should be included as a possible complication of surgical management.

Coexistence of VHL Disease and CPT2 Deficiency: A Case Report.

von Hippel-Lindau (VHL) disease is an inherited syndrome manifesting with benign and malignant tumors. Deficiency of carnitine palmitoyltransferase type II (CPT2) is a disorder of lipid metabolism that, in the muscle form, manifests with recurrent attacks of myalgias often associated with myoglobinuria. Rhabdomyolytic episodes may be complicated by life-threatening events, including acute renal failure (ARF). We report on a male patient who was tested, at 10 years of age, for VHL disease because of family history of VHL. He was diagnosed with VHL but without VHL-related manifestation at the time of diagnosis. During childhood, the patient was hospitalized several times for diffuse muscular pain, muscle weakness, and dark urine. These recurrent attacks of rhabdomyolysis were never accompanied by ARF. The patient was found to be homozygous for the mutation p.S113L of the CPT2 gene. To the best of our knowledge, this is the first report of the coexistence of VHL disease and CPT2 deficiency in the same individual. Based on findings from animal models, the case illustrates that mutations in the VHL gene might protect against renal damage caused by CPT2 gene mutations.

PARS PLANA VITRECTOMY IN ADVANCED CASES OF VON HIPPEL-LINDAU EYE DISEASE.

PURPOSE: To investigate spectrum of patients with Von Hippel-Lindau disease (VHL) that required pars plana vitrectomy and evaluate anatomical and functional outcomes of surgery. METHODS: Twenty-three patients who underwent surgery for advanced VHL eye disease were assessed by genetic tests, diagnostic tests for systemic lesions, and clinical eye examination. The vitrectomized eyes were divided into two groups: with or without retinotomy (group R vs. NR). Functional and anatomical outcome was analyzed and compared between the groups. RESULTS: All patients had central nervous system hemangioblastomas and 57% had other systemic tumors. Point germline mutations, large partial deletions, and complete vhl gene deletions were found in 64%, 27%, and 9% of patients, accordingly. Destruction of hemangioblastomas by retinotomy, laser, or cryotherapy and anatomical attachment of the retina were achieved in all eyes. Preoperative mean distance best-corrected visual acuity was logarithm of the minimum angle of resolution 2.66 (20/9,140) in group R and 1.76 (20/1,150) in group NR (P < 0.05). At 6 months postoperatively, distance best-corrected visual acuity improved in 20 eyes (83%). After over 24 months postoperatively, distance best-corrected visual acuity remained better than preoperatively in 36% in the R group and in 70% in the NR group of eyes. During 24 months postoperatively in 17 eyes, new retinal capillary hemangiomas developed. The mean number of new retinal capillary hemangiomas per eye was higher in group R than in group NR (3.14 vs. 0.70; P < 0.01). In group R, number of new retinal capillary hemangioblastoma was higher in retinal segments where retinotomy was performed (n = 29) than in other areas (n = 13) (P < 0.01). CONCLUSION: Advanced VHL eye disease correlates with occurrence of central nervous system and systemic lesions. Spectrum of vhl gene mutation in the patients corresponds to that of the general VHL population. Pars plana vitrectomy in advanced VHL eye disease can improve or preserve visual function, but postoperative progression of ocular VHL disease can be accelerated in cases where retinotomy is performed.

Recurrent multiple CNS hemangioblastomas with VHL disease treated with pazopanib: a case report and literature review.

Hemangioblastoma is a rare benign neoplasm, accounting for less than 2% of all primitive brain tumors. It may arise sporadically in a solitary form, or associated with Von Hippel-Lindau (VHL) disease with multiple tumors. Surgery is the mainstay treatment, but management is challenging in case of recurrent and/or multiple tumors. VHL protein is defective in both forms of hemangioblastoma, leading to the accumulation of hypoxia-inducible factor, stimulating angiogenesis via VEGF and PDGF mainly. Here, we report a 37-year-old woman's case with recurrent and rapidly progressive VHL-associated hemangioblastomas, causing severe disability. She was treated 24 months with pazopanib, a multityrosine kinase inhibitor (TKI) targeting VEGF and PDGF-ß pathways. Despite moderate radiological changes, progressive improvement in her clinical condition persisting over 3 years was observed. Inhibiting angiogenesis is a therapeutic option that may improve the quality of life and the autonomy of VHL patients disabled with multiple hemangioblastomas.

Pharmacological HIF2α inhibition improves VHL disease-associated phenotypes in zebrafish model.

Patients with a germline mutation in von Hippel-Lindau (VHL) develop renal cell cancers and hypervascular tumors of the brain, adrenal glands, and pancreas as well as erythrocytosis. These phenotypes are driven by aberrant expression of HIF2α, which induces expression of genes involved in cell proliferation, angiogenesis, and red blood cell production. Currently, there are no effective treatments available for VHL disease. Here, using an animal model of VHL, we report a marked improvement of VHL-associated phenotypes following treatment with HIF2α inhibitors. Inactivation of vhl in zebrafish led to constitutive activation of HIF2α orthologs and modeled several aspects of the human disease, including erythrocytosis, pathologic angiogenesis in the brain and retina, and aberrant kidney and liver proliferation. Treatment of vhl(-/-) mutant embryos with HIF2α-specific inhibitors downregulated Hif target gene expression in a dose-dependent manner, improved abnormal hematopoiesis, and substantially suppressed erythrocytosis and angiogenic sprouting. Moreover, pharmacologic inhibition of HIF2α reversed the compromised cardiac contractility of vhl(-/-) embryos and partially rescued early lethality. This study demonstrates that small-molecule targeting of HIF2α improves VHL-related phenotypes in a vertebrate animal model and supports further exploration of this strategy for treating VHL disease.

MicroRNAs in the pathogenesis of cystic kidney disease.

PURPOSE OF REVIEW: Cystic kidney diseases are common renal disorders characterized by the formation of fluid-filled epithelial cysts in the kidneys. The progressive growth and expansion of the renal cysts replace existing renal tissue within the renal parenchyma, leading to reduced renal function. While several genes have been identified in association with inherited causes of cystic kidney disease, the molecular mechanisms that regulate these genes in the context of post-transcriptional regulation are still poorly understood. There is increasing evidence that microRNA (miRNA) dysregulation is associated with the pathogenesis of cystic kidney disease. RECENT FINDINGS: In this review, recent studies that implicate dysregulation of miRNA expression in cystogenesis will be discussed. The relationship of specific miRNAs, such as the miR-17∼92 cluster and cystic kidney disease, miR-92a and von Hippel-Lindau syndrome, and alterations in LIN28-LET7 expression in Wilms tumor will be explored. SUMMARY: At present, there are no specific treatments available for patients with cystic kidney disease. Understanding and identifying specific miRNAs involved in the pathogenesis of these disorders may have the potential to lead to the development of novel therapies and biomarkers.

Intracranial pressure monitoring and caesarean section in a patient with von Hippel-Lindau disease and symptomatic cerebellar haemangioblastomas.

Von Hippel-Lindau disease is a rare genetic disorder which gives rise to a range of tumours including central nervous system haemangioblastomas. We report a case of caesarean section in a patient with symptomatic cerebellar haemangioblastomas associated with von Hippel-Lindau disease. An intracranial pressure monitor was inserted before surgery, which enabled intracranial pressure to be monitored throughout. The anaesthetic implications of von Hippel-Lindau disease are discussed and clinical options explored.

Genotype-phenotype correlations, and retinal function and structure in von Hippel-Lindau disease.

PURPOSE: To investigate genotype-phenotype correlation and to analyze functional and structural changes in the retina of patients with von Hippel-Lindau (VHL) disease. METHODS: Thirteen patients from four families (A, B, C and D) with known VHL disease and known mutations in the VHL gene were examined. All patients underwent clinical examination and optical coherence tomography (OCT). Full-field electroretinography (full-field ERG) was performed in twelve patients. RESULTS: Family A, with deletion of exon 3 in the VHL gene, and family B, with the missense mutation p.R79P, exhibited type 1 VHL characterized by the absence of pheochromocytoma and a high incidence of central nervous system hemangioblastomas. One member of family B exhibited Goldenhar syndrome. A novel missense mutation (p.L198P) was identified in the VHL gene in the patient from family C. This p.L198P mutation caused a phenotype with early onset of a neuroendocrine tumor of the pancreas, bilateral pheochromocytomas, and optic nerve hemangioblastoma. Full-field ERG showed significantly prolonged implicit times of the b-wave and maximal combined a-wave in VHL patients, compared to controls. Examination of the retinal structure in all patients with VHL, using OCT, showed a significant decrease in retinal thickness in VHL patients without ocular hemangioblastomas, compared to controls. CONCLUSIONS: Our findings support previously established genotype-phenotype correlations. However, we here describe an unusual phenotype with a novel missense mutation, p.L198P, and report the finding that VHL disease can be associated with Goldenhar syndrome. Electrophysiological and structural findings suggest that VHL disease is a progressive, neurodegenerative disease of the retina.

von Hippel-Lindau syndrome.

von Hippel-Lindau (VHL) disease is an autosomal-dominant familial cancer syndrome associated with mutations of the VHL tumor suppressor gene (3p25-26). Its estimated incidence ranges from 1 in 36,000 to 1 in 53,000 with a penetrance of up to 95% by age 60. Genotype-phenotype correlation divides VHL into two broad clinical subtypes. Type 1 VHL is predominantly associated with large deletion or truncation mutations which result in an encoded protein with very little or no activity. It is associated with retinal and CNS hemangioblastoma and renal cell carcinoma but not pheochromocytoma. Type 2 is usually associated with missense mutations encoding a protein with limited activity and includes pheochromocytoma. It is further classified into three other subtypes (2A, 2B, 2C) based on the presence of hemangioblastoma and renal cell carcinoma. Visceral cysts in the kidney, pancreas and epididymis, nonfunctioning pancreatic neuroendocrine tumors which often show distinctive clear cell cytology, endolymphatic sac tumors and head and neck paragangliomas are well recognized but less common presenting features. Surveillance of carriers can reduce the burden of disease and is best performed in specialist referral centers with due consideration given to both the complex molecular pathogenesis and psychosocial aspects of the disease.

Perioperative management of pheochromocytoma and catecholamine-induced dilated cardiomyopathy in a pediatric patient.

Dilated cardiomyopathy resulting from pheochromocytoma-mediated catecholamine excess poses a unique challenge to heart failure management. Although early screening of patients with familial neoplastic syndromes at risk for pheochromocytoma may facilitate early resection, the resultant manifestations of prolonged catecholamine excess among patients with undiagnosed pheochromocytoma may lead to myocardial fibrosis with both systolic and diastolic dysfunction. Furthermore, the hemodynamic effects of catecholamine excess exacerbate the risks of perioperative hemodynamic instability in the setting of such myocardial depression. This report describes an approach to the perioperative care of a child who had pheochromocytoma and catecholamine-induced cardiomyopathy with ventricular dysfunction refractory to medical management.

Longitudinal analysis of retinal hemangioblastomatosis and visual function in ocular von Hippel-Lindau disease.

OBJECTIVE: Characterization of the structural and functional progression of ocular von Hippel-Lindau (VHL) disease and analysis of patient factors influencing disease progression. DESIGN: Retrospective analysis of a case series from a longitudinal, observational study. PARTICIPANTS: Two hundred forty-nine participants with clinically defined systemic VHL disease and more than 2 years of ophthalmic follow-up. METHODS: Standardized scoring of ocular phenotype and systemic characteristics was performed at each study visit and was analyzed longitudinally to determine progression of ocular VHL disease. MAIN OUTCOME MEASURES: Measures evaluated include: visual acuity, features of ocular VHL disease (presence, location, number, and extent of retinal capillary hemangioblastomas [RCHs]), germline mutation in the VHL gene, demographics (age, gender, age at onset of ocular disease), and patient characteristics (smoking status, body mass index). RESULTS: Most participants demonstrated relative anatomic and functional stability in ocular VHL disease status over a mean follow-up of 8.2 ± 4.0 years. Approximately three quarters (73%) of participants without ocular VHL disease at baseline remained disease free at the end of follow-up. Among eyes with ocular VHL disease at baseline, 88% did not demonstrate RCHs in a new retinal location, 70% remained stable in RCH number, and 79% remained stable in the extent of RCH involvement. Mean visual acuity for all study eyes (n = 498) decreased by 5.1 ± 0.6 letters across follow-up, with 16.1% of study eyes decreasing by more than 10 letters in visual acuity. Among eyes affected at baseline, greater vision loss was associated with the presence of juxtapapillary RCHs, development of RCH in a new location, and increase in peripheral RCH number and extent. Younger baseline age, younger age at onset of ocular VHL disease, involvement of the fellow eye with ocular VHL disease, and missense or protein-truncating germline mutations were associated significantly with increased anatomic involvement and functional deterioration. CONCLUSIONS: Patients with ocular VHL disease maintain relative anatomic and functional stability, with only a minority demonstrating marked anatomic progression and vision loss. Systemic and ocular risk factors for anatomic progression and vision loss can help practitioners identify patients with a higher risk profile for counseling, closer follow-up, and proactive treatment. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Systemic VHL gene functions and the VHL disease.

The von Hippel-Lindau tumor suppressor gene (VHL) is best known as an E3 ubiquitin ligase that negatively regulates the hypoxia inducible factor (HIF). VHL mutations are the genetic defects underlying several human diseases including polycythemia, familial VHL tumor syndrome and sporadic renal cell carcinoma. VHL mutations can lead to cell-autonomous phenotypes in the tumor cells. However, non-tumor cell-autonomous functions of VHL have also been noted. VHL tumor-derived cytokines can promote inflammation and induce mobilization of endothelial progenitor cells. Up-regulation of HIF caused by VHL loss-of-function mutants, including heterozygotes, has been shown to increase the activities of hematopoietic stem cells, endothelial cells and myeloid cells. As such, systemic functions of VHL likely play important roles in the development of VHL disease.