A Role for PPARβ/δ in Tumor Stroma and Tumorigenesis

Peroxisome proliferator-activated receptor-β/δ (PPARβ/δ) is a transcription factor that is activated by endogenous fatty acid ligands and by synthetic agonists. Its role in the regulation of skeletal muscle fatty acid catabolism, glucose homeostasis, and cellular differentiation has been established in multiple studies. On the contrary, a role for PPARβ/δ in tumorigenesis is less clear because there are contradictory reports in the literature. However, the majority of these studies have not examined the role of PPARβ/δ in the tumor stroma. Recent evidence suggests that stromal PPARβ/δ regulates tumor endothelial cell proliferation and promotes differentiation leading to the properly orchestrated events required for tumor blood vessel formation. This review briefly summarizes the significance of these studies that may provide clues to help explain the reported discrepancies in the literature regarding the role of PPARβ/δ in tumorigenesis

Cyclooxygenase-2 expression is associated with the renal macula densa of patients with Bartter-like syndrome

Cyclooxygenase-2 expression is associated with the renal macula densa of patients with Bartter-like syndrome.BackgroundBartter-like syndrome (BLS) is a heterogeneous set of congenital tubular disorders that is associated with significant renal salt and water loss. The syndrome is also marked by increased urinary prostaglandin E2 (PGE2) excretion. In rodents, salt and volume depletion are associated with increased renal macula densa cyclooxygenase-2 (COX-2) expression. The expression of COX-2 in human macula densa has not been demonstrated. The present studies examined whether COX-2 can be detected in macula densa from children with salt-wasting BLS versus control tissues.MethodsThe intrarenal distribution of COX-2 protein and mRNA was analyzed by immunohistochemistry and in situ hybridization in 12 patients with clinically and/or genetically confirmed BLS. Renal tissue rejected for transplantation, from six adult patients not affected by BLS, was also examined.ResultsThe expression of COX-2 immunoreactive protein was observed in cells of the macula densa in 8 out 11 patients with BLS. In situ hybridization confirmed the expression of COX-2 mRNA in the macula densa in 6 out of 10 cases. COX-2 protein was also detected in the macula densa in a patient with congestive heart failure. The expression of COX-2 immunoreactive protein was not observed in cells associated with the macula densa in kidneys from patients without disorders associated with hyper-reninemia.ConclusionThese studies demonstrate that COX-2 may be detected in the macula densa of humans. Since macula densa COX-2 was detected in cases of BLS, renal COX-2 expression may be linked to volume and renin status in humans, as well as in animals

Long-read sequencing identifies a common transposition haplotype predisposing for CLCNKB deletions

BACKGROUND: Long-read sequencing is increasingly used to uncover structural variants in the human genome, both functionally neutral and deleterious. Structural variants occur more frequently in regions with a high homology or repetitive segments, and one rearrangement may predispose to additional events. Bartter syndrome type 3 (BS 3) is a monogenic tubulopathy caused by deleterious variants in the chloride channel gene CLCNKB, a high proportion of these being large gene deletions. Multiplex ligation-dependent probe amplification, the current diagnostic gold standard for this type of mutation, will indicate a simple homozygous gene deletion in biallelic deletion carriers. However, since the phenotypic spectrum of BS 3 is broad even among biallelic deletion carriers, we undertook a more detailed analysis of precise breakpoint regions and genomic structure. METHODS: Structural variants in 32 BS 3 patients from 29 families and one BS4b patient with CLCNKB deletions were investigated using long-read and synthetic long-read sequencing, as well as targeted long-read sequencing approaches. RESULTS: We report a ~3 kb duplication of 3'-UTR CLCNKB material transposed to the corresponding locus of the neighbouring CLCNKA gene, also found on ~50 % of alleles in healthy control individuals. This previously unknown common haplotype is significantly enriched in our cohort of patients with CLCNKB deletions (45 of 51 alleles with haplotype information, 2.2 kb and 3.0 kb transposition taken together, p=9.16×10-9). Breakpoint coordinates for the CLCNKB deletion were identifiable in 28 patients, with three being compound heterozygous. In total, eight different alleles were found, one of them a complex rearrangement with three breakpoint regions. Two patients had different CLCNKA/CLCNKB hybrid genes encoding a predicted CLCNKA/CLCNKB hybrid protein with likely residual function. CONCLUSIONS: The presence of multiple different deletion alleles in our cohort suggests that large CLCNKB gene deletions originated from many independently recurring genomic events clustered in a few hot spots. The uncovered associated sequence transposition haplotype apparently predisposes to these additional events. The spectrum of CLCNKB deletion alleles is broader than expected and likely still incomplete, but represents an obvious candidate for future genotype/phenotype association studies. We suggest a sensitive and cost-efficient approach, consisting of indirect sequence capture and long-read sequencing, to analyse disease-relevant structural variant hotspots in general

Atypical hemolytic uremic syndrome in children: complement mutations and clinical characteristics

Item does not contain fulltextBACKGROUND: Mutations in complement factor H (CFH), factor I (CFI), factor B (CFB), thrombomodulin (THBD), C3 and membrane cofactor protein (MCP), and autoantibodies against factor H (alphaFH) with or without a homozygous deletion in CFH-related protein 1 and 3 (CFHR1/3) predispose development of atypical hemolytic uremic syndrome (aHUS). METHODS: Different mutations in genes encoding complement proteins in 45 pediatric aHUS patients were retrospectively linked with clinical features, treatment, and outcome. RESULTS: In 47% of the study participants, potentially pathogenic genetic anomalies were found (5xCFH, 4xMCP, and 4xC3, 3xCFI, 2xCFB, 6xalphaFH, of which five had CFHR1/3); four patients carried combined genetic defects or a mutation, together with alphaFH. In the majority (87%), disease onset was preceeded by a triggering event; in 25% of cases diarrhea was the presenting symptom. More than 50% had normal serum C3 levels at presentation. Relapses were seen in half of the patients, and there was renal graft failure in all except one case following transplant. CONCLUSIONS: Performing adequate DNA analysis is essential for treatment and positive outcome in children with aHUS. The impact of intensive initial therapy and renal replacement therapy, as well as the high risk of recurrence of aHUS in renal transplant, warrants further understanding of the pathogenesis, which will lead to better treatment options.01 augustus 201

Kopplung der Cyclooxygenase 2 an sekundäre Enzyme

Die NSAR gehören zu den weltweit am häufigsten eingenommenen Schmerzmedikamenten. Sie hemmen die Cylooxygenase 1 und 2, Enzyme, die für die Produktion von Schmerzmediatoren (Prostaglandine) verantwortlich sind. Durch die unselektive Hemmung beider Cylooxygenasen kommt es jedoch auch zu der Hemmung des physiologischen Wirkungsspektrums der Cyclooxygenase 1, z.B. dem Schutz der Magenmukosa. Dies kann zu unerwünschten Nebenwirkungen, wie z.B. Magenschleimhautblutungen, führen. Da die Cyclooxygenase 2 im Gegensatz zu der Cyclooxygenase 1 weniger bzw. andere physiologische Funktionen übernimmt und in erhöhtem Maße in entzündetem Gewebe exprimiert wird, wurden selektive Cyclooxygenase 2 – Hemmer entwickelt. Leider zeigten sich in der klinischen Anwendung dieser selektiven Inhibitoren nach Jahren kardiovaskuläre Komplikationen. Eine mögliche Ursache dieser Komplikationen könnte in der Präferenz der Cyclooxygenase 2 zur Prostazyklin-Synthase und somit zur Prostazyklin-Bildung liegen. Prostazyklin ist ein vaskulär-protektives Eikosanoid, welches die Thrombozytenaggregation hemmt und vasodilatierend wirkt. Eine Verminderung des Prostazyklins kann also thromboembolische Komplikationen verursachen. Warum aber gerade die Prostazyklin-Synthase vorrangig mit der Cyclooxygenase 2 statt mit der Cyclooxygenase 1 arbeitet, ist bisher noch nicht geklärt. Eine mögliche Ursache könnte in einem strukturellen Unterschied der beiden Enzyme liegen. Obwohl die Cyclooxygenasen in Ihren Sequenzen eine Homologie von 60 % aufweisen, findet sich ein auffallender Unterschied in der Struktur des C-terminalen Endes. Die Cyclooxygenase 2 weist hier einen Einschub von 18 Aminosäuren auf, welche sich im C-terminalen Ende der Cyclooxygenase 1 nicht finden lässt. Daher wurde im Rahmen dieser Dissertation das C-terminale Ende der Cyclooxygenase 2 zunächst durch sieben Punktmutationen verändert. Die Veränderungen bezogen sich sowohl auf die Struktur als auch auf die Hydrophobizität, den Säuregrad und die Polarität bzw. den Ladungszustand des Enzyms. Darüber hinaus wurden zwei Deletionsmutationen durchgeführt, bei der der C-Terminus der Cyclooxygenase 2 zum einen zur Hälfte, zum anderen ganz entfernt wurde. Alle neun Mutanten wurden in ein Zellsystem (HEK 293) transformiert, die Überstände auf die Prostazyklin- und PGE2-Produktion untersucht und mit Hilfe des Western-Blot-Verfahren überprüft. Die Untersuchungen ergaben, dass sich die Produktionen des Prostazyklins und des PGE2 bei den Punktmutationen nur in ihrer gesamten Menge, nicht aber im Verhältnis Prostazyklin zu PGE2 veränderten. Die Deletionsmutanten zeigten jedoch einen Rückgang der Prostazyklin- Produktion in der Gesamtmenge und im Verhältnis zu PGE2. Die Deletion der Hälfte bzw. des ganzen C-Terminus der Cyclooxygenase hat also zu einer veränderten Prostazyklin-Produktion geführt. Diese Daten weisen daraufhin, dass der C-Terminus für die Präferenz der Cyclooxygenase 2 bezüglich der Prostazyklin-Synthase eine entscheidende Rolle spielen könnte. Es bedarf weiterer Forschungen, um eine etwaige Verbindung der Prostazyklin- Synthase und des C-Terminus der Cyclooxygenase 2 noch genauer zu untersuchen. Die vollständige Aufklärung dieser Präferenz ist in Bezug auf eine Schmerztherapie ohne mögliche Komplikationen für die Zukunft von großer klinischer Bedeutung

Hyporeninemic hypoaldosteronism in RMND1-related mitochondrial disease

Background: RMND1 is a nuclear gene needed for proper function of mitochondria. A pathogenic gene will cause multiple oxidative phosphorylation defects. A renal phenotype consisting of hyponatremia, hyperkalemia, and acidosis is frequently reported, previously considered to be due to aldosterone insensitivity. Methods: Clinical features and pathophysiology of three patients will be reported. DNA of these patients was subjected to exome screening. Results: In the first family, one pathogenic heterozygous and one highly probable heterozygous mutation were detected. In the second family, a homozygous pathogenic mutation was present. The electrolyte disbalance was not due to aldosterone insensitivity but to low plasma aldosterone concentration, a consequence of low plasma renin activity. This disbalance can be treated. In all three patients, the kidney function declined. In the first family, both children suffered from an unexplained arterial thrombosis with dire consequences. Conclusions: Hyporeninemic hypoaldosteronism is the mechanism causing the electrolyte disbalance reported in patients with RMND1 mutations, and can be treated.</p

Hyporeninemic hypoaldosteronism in RMND1-related mitochondrial disease

Background: RMND1 is a nuclear gene needed for proper function of mitochondria. A pathogenic gene will cause multiple oxidative phosphorylation defects. A renal phenotype consisting of hyponatremia, hyperkalemia, and acidosis is frequently reported, previously considered to be due to aldosterone insensitivity. Methods: Clinical features and pathophysiology of three patients will be reported. DNA of these patients was subjected to exome screening. Results: In the first family, one pathogenic heterozygous and one highly probable heterozygous mutation were detected. In the second family, a homozygous pathogenic mutation was present. The electrolyte disbalance was not due to aldosterone insensitivity but to low plasma aldosterone concentration, a consequence of low plasma renin activity. This disbalance can be treated. In all three patients, the kidney function declined. In the first family, both children suffered from an unexplained arterial thrombosis with dire consequences. Conclusions: Hyporeninemic hypoaldosteronism is the mechanism causing the electrolyte disbalance reported in patients with RMND1 mutations, and can be treated.</p