TFEB drives mTORC1 hyperactivation and kidney disease in Tuberous Sclerosis Complex.

Tuberous Sclerosis Complex (TSC) is caused by TSC1 or TSC2 mutations, leading to hyperactivation of mechanistic target of rapamycin complex 1 (mTORC1) and lesions  in multiple organs including lung (lymphangioleiomyomatosis) and kidney (angiomyolipoma and renal cell carcinoma). Previously, we found that TFEB is constitutively active in TSC. Here, we generated two mouse models of TSC in which kidney pathology is the primary phenotype. Knockout of TFEB rescues kidney pathology and overall survival, indicating that TFEB is the primary driver of renal disease in TSC. Importantly, increased mTORC1 activity in the TSC2 knockout kidneys is normalized by TFEB knockout. In TSC2-deficient cells, Rheb knockdown or Rapamycin treatment paradoxically increases TFEB phosphorylation at the mTORC1-sites and relocalizes TFEB from nucleus to cytoplasm. In mice, Rapamycin treatment normalizes lysosomal gene expression, similar to TFEB knockout, suggesting that Rapamycin's benefit in TSC is TFEB-dependent. These results change the view of the mechanisms of mTORC1 hyperactivation in TSC and may lead to therapeutic avenues.

ZO-1 expression in normal human macula densa: Immunohistochemical and immunofluorescence investigations.

The macula densa (MD) is an anatomical structure having a plaque shape, placed in the distal end of thick ascending limb of each nephron and belonging to juxtaglomerular apparatus (JGA). The aim of the present investigation is to investigate the presence of ZO-1, a specific marker of tight juncions (TJs), in MD cells. Six samples of normal human renal tissue were embedded in paraffin for ZO-1 expression analysis by immunohistochemical and immunofluorescence techniques. We detected ZO-1 expression in the apical part of cell membrane in MD cells by immunohistochemistry. In addition, ZO-1 and nNOS expressions (a specific marker of MD) were colocalized in MD cells providing clear evidence of TJs presence in normal human MD. Since ZO-1 is responsible for diffusion barrier formation, its presence in the MD supports the existence of a tubulomesangial barrier that ensures a regulated exchange between MD and JGA effectors in renal and glomerular haemodynamic homeostasis.

Neuronal nitric oxide synthase positive neurons in the human corpus callosum: a possible link with the callosal blood-oxygen-level dependent (BOLD) effect.

Brain functions have been investigated in the past decades via the blood-oxygen-level dependent (BOLD) effect using functional magnetic resonance imaging. One hypothesis explaining the BOLD effect involves the Nitric Oxide (NO) gaseous neurotransmitter, possibly released also by cells in the corpus callosum (CC). The eventual presence of NO releasing neurons and/or glial cells in the CC can be assessed by immunohistochemistry. Serial sections both from paraffin-embedded and frozen samples of CC obtained from adult human brains autopsy were studied with immunohistochemistry and immunofluorescence analysis, using an antibody against the neuronal isoform of Nitric Oxide Synthase (nNOS), the enzyme synthetizing the NO. The staining revealed the presence of many nNOS-immunopositive cells in the CC, shown to be neurons with immunofluorescence. Neuronal NOS-positive neurons presented different morphologies, were more numerous 4 mm apart from the midline, and displayed a peak in the body of the CC. In some cases, they were located at the upper boundary of the CC, more densely packed in the proximity of the callosal arterioles. The significant presence of nNOS-immunopositive neurons within the commissure suggests their probable role in the CC neurovascular regulation in the adult brain and could explain the BOLD effect detected in human CC.

Scattered Tubular Cells Markers in Macula Densa of Normal Human Adult Kidney.

BACKGROUND: The scattered tubular cells (STCs) are a population of resident progenitor tubular cells with expansion, self-renewal and epithelial differentiation abilities. Although these cells are localized within the proximal (PTs) and distal (DTs) tubules in a normal adult kidney, their presence has never been demonstrated in human macula densa (MD). The purpose of the present study is to describe the presence of STCs in MD using specific markers such as prominin-1 (CD133), cytokeratin 7 (KRT7) and vimentin (VIM). METHODS: We analyzed two sets of three consecutive serial sections for each sample. The first sections of each set were immunostained for nNOS to identify MD, the second sections were immune-stained for CD133 (specific STCs marker) while the third sections were analyzed for KRT7 (another STCs specific marker) and VIM (that stains the basal pole of the STCs) in the first and second sets, respectively, in order to study the co-expression of KRT7 and VIM with the CD133 marker. RESULTS: CD133 was localized in some MD cells and in the adjacent DT cells. Moreover, CD133 was detected in the parietal epithelial cells of Bowman's capsule and in some proximal tubules (PT). KRT7-positive cells were identified in MD and adjacent DT cells, while KRT7 positivity was mostly confined in both DT and collecting ducts (CD) in the other areas of the renal parenchyma. CD133 and KRT7 were co-expressed in some MD and adjacent DT cells. Some of the latter cells were positive both for CD133 and VIM. CD133 was always localized in the apical part of the cells, whereas the VIM expression was evident only in the cellular basal pole. Although some cells of MD expressed VIM or CD133, none of them co-expressed VIM and CD133. CONCLUSIONS: The presence of STCs was demonstrated in human adult MD, suggesting that this structure has expansion, self-renewal and epithelial differentiation abilities, similar to all other parts of renal tubules.

Case Report: Optic Atrophy and Nephropathy With m.13513G>A/MT-ND5 mtDNA Pathogenic Variant.

Isolated complex I deficiency represents the most common mitochondrial respiratory chain defect involved in mitochondrial disorders. Among these, the mitochondrial DNA (mtDNA) m.13513G>A pathogenic variant in the NADH dehydrogenase 5 subunit gene (MT-ND5) has been associated with heterogenous manifestations, including phenotypic overlaps of mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes, Leigh syndrome, and Leber's hereditary optic neuropathy (LHON). Interestingly, this specific mutation has been recently described in patients with adult-onset nephropathy. We, here, report the unique combination of LHON, nephropathy, sensorineural deafness, and subcortical and cerebellar atrophy in association with the m.13513G>A variant.

Neuronal nitric oxyde synthase positive neurons in human indusium griseum.

The study was designed to analyze the nNOS positive neurons present in the indusium griseum by describing their distribution and morphology. To this purpose, sagittal serial sections from paraffin or frozen autopsy specimens of corpus callosum including the overlying indusium griseum were processed by immunohistochemistry and immunofluorescence, using an antibody against the neuronal form of the enzyme nitric oxyde synthase. To test the specificity of the antibody used, Western Blot was performed in the indusium griseum of the same specimens. The stainings revealed the presence of many neuronal nitric oxyde synthase-immunopositive neurons in human indusium griseum, located along both rostral-caudal and medio-lateral directions. In particular, they were more numerous 1 mm apart from the midline, and their number peaked over the body of the corpus callosum. They showed different morphologies; in some cases, they were located at the boundary between indusium griseum and corpus callosum, more densely packed in proximity to the pial arteries penetrating into the corpus callosum. The significant presence and distribution of neuronal nitric oxyde synthase-immunopositive neurons suggests that indusium griseum likely plays a functional role in the neurovascular regulation within the corpus callosum. Schematic representation of human adult IG and the neurovascular unit originating from sopracallosal artery (Sca) that branches into smaller arterioles (Br) (created in PowerPoint). The arterioles cross the three layers of IG (layers I, II and III) and penetrate into the CC separated from IG by the Virchow-Robin space (VRs). As the arterioles go deeper, this space disappears and the vascular basement membrane comes into direct contact with the astrocytic end-feets (intracallosal arterioles and capillaries). nNOS-immunopositive neurons (nNOSIP N) surround the arterioles and control the vasomotore tone secreting nitric oxyde (NO). Two morphological types of nNOSIP N can be appreciated by the use of different colors: fusiform (blue) and ovoidal (pink). Also NeuN-immunopositive neurons (N) and many astrocytes (As) are present, more numerous in IG than in CC.

Identification of multinucleated cells in human kidney cortex: A way for tissue repairing?

The presence of multinucleated cells has never been demonstrated in renal tissue, although, polyploid cells were recently observed in the tubules of normal and pathological human kidney. Therefore, the aim of the present study is to identify and quantify, by electron microscopy, multinucleated cells in the cortical tissue of normal human kidney i.e., in the three compartments of renal tubule: the proximal tubule (PT), the distal tubule (DT), and the collecting duct (CD), as well as, in the glomerulus (podocytes). The percentage of the multinucleated cells observed was 5% (95%CI: 3.6%-6.7%) in renal cortical tubules with distribution in each tubular compartment of 6% in PT, 4% in DT and 3% in CD with no statistically significant difference in the distribution of multinucleated cells according to tubular compartments. Four percent of analysed podocytes (in total 149 podocytes) were multinucleated (95%CI: 1.5%-8.6%). In conclusion, multinucleated cells were identified and quantified in functionally normal kidneys, as previously demonstrated in other organs such as the liver.

ANCA-Associated Glomerulonephritis and Anti-Phospholipid Syndrome in a Patient with SARS-CoV-2 Infection: Just a Coincidence?

Many reports have described a high incidence of acute kidney injury (AKI) among patients with COVID-19. Acute tubular necrosis has been reported to be the most common damage in these patients, probably due to hemodynamic instability. However, other complex processes may be involved, related to the cytokine storm and the activation of innate and adaptive immunity. Here, we describe a patient who developed an antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis with rapidly progressive glomerulonephritis and lung involvement and an antiphospholipid syndrome soon after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. After viral pneumonia was excluded by bronchoalveolar lavage, the patient has been treated with rituximab for amelioration of kidney function and resolution of thrombosis without any adverse event. We conclude that COVID-19 may trigger autoimmune diseases including ANCA-associated vasculitis. Thus, this diagnosis should be taken in consideration in COVID-19 patients, especially when they develop AKI with active urinary sediment. In addition, considering the relationship between these 2 diseases, SARS-CoV-2 infection should be excluded in all patients with a new diagnosis ANCA-associated vasculitis before starting immunosuppressive therapy.

TSC2 regulates lysosome biogenesis via a non-canonical RAGC and TFEB-dependent mechanism.

Tuberous Sclerosis Complex (TSC) is caused by TSC1 or TSC2 mutations, resulting in hyperactivation of the mechanistic target of rapamycin complex 1 (mTORC1). Transcription factor EB (TFEB), a master regulator of lysosome biogenesis, is negatively regulated by mTORC1 through a RAG GTPase-dependent phosphorylation. Here we show that lysosomal biogenesis is increased in TSC-associated renal tumors, pulmonary lymphangioleiomyomatosis, kidneys from Tsc2+/- mice, and TSC1/2-deficient cells via a TFEB-dependent mechanism. Interestingly, in TSC1/2-deficient cells, TFEB is hypo-phosphorylated at mTORC1-dependent sites, indicating that mTORC1 is unable to phosphorylate TFEB in the absence of the TSC1/2 complex. Importantly, overexpression of folliculin (FLCN), a GTPase activating protein for RAGC, increases TFEB phosphorylation at the mTORC1 sites in TSC2-deficient cells. Overexpression of constitutively active RAGC is sufficient to relocalize TFEB to the cytoplasm. These findings establish the TSC proteins as critical regulators of lysosomal biogenesis via TFEB and RAGC and identify TFEB as a driver of the proliferation of TSC2-deficient cells.

IgA Deficiency and Membranoproliferative Glomerulonephritis: A Case Report.

BACKGROUND: Immunoglobulin A deficiency (IgAD) is the most common form of primary immunodeficiency in western countries. It can be associated with the development of autoimmune diseases both in adults and in children even though the exact pathophysiology is not fully defined. CASE PRESENTATION: We report here a case of a young patient who developed nephrotic syndrome secondary to membranoproliferative glomerulonephritis associated with the incidental finding of IgAD. We began corticosteroid therapy and angiotensin-converting enzyme inhibitor, and we observed partial remission of the nephrotic syndrome after about nine months; nonetheless, in the following follow-up visits, a progressive decline of renal function was found. CONCLUSION: Our case extends the spectrum of hitherto described glomerulonephritides associated with IgAD which were described until now.

Hypoxia-induced expression of neuronal nitric oxide synthase in astrocytes of human corpus callosum.

Nitric oxide (NO) is a gaseous neurotransmitter largely diffused in the brain; among other functions, it regulates the cerebral blood flow in response to hypoxia. NO can be synthetized by three different isoforms of the enzyme NO synthase: neuronal (nNOS), typical of neurons, endothelial and inducible. The aim of this study was to assess nNOS expression in human corpus callosum (CC) astrocytes, and its relationship with the hypoxia duration. Autoptic samples of CC from adult human subjects have been processed with immunohistochemistry and immunofluorescence using antibodies anti-nNOS and anti-glial fibrillary acidic protein (GFAP), the astrocyte marker. Results demonstrated for the first time the presence of nNOS-immunopositive astrocytes in the human CC. In particular, nNOS-positive astrocytes were absent in subjects deceased after a short hypoxia; their number and labeling intensity, however, increased with hypoxia prolongation. Neuronal NOS immunopositivity of CC astrocytes seems thus related to the hypoxia duration and the consequent brain damage.

Nephrotoxicity Associated with Novel Anticancer Agents (Aflibercept, Dasatinib, Nivolumab): Case Series and Nephrological Considerations.

Cancer patients have an incidence of about 60% kidney disease development and are at elevated risk of acute renal damage. Kidney disease in these patients is frequently associated with nephrotoxicity from the ongoing oncological treatment. New anticancer therapeutic strategies, such as targeted therapies and immunotherapies, offer substantial benefits in the treatment of many neoplasms. However, their use is associated with significant nephrotoxicity, which qualitatively differs from that seen with traditional cytotoxic chemotherapy, while the underlying mechanisms are complex and still to be clearly defined. Nephrologists need to be knowledgeable about the array of such renal toxicities for effective collaboration with the oncologist in the prevention and management of kidney involvement. Renal adverse effects may range from asymptomatic proteinuria to renal failure, and their prompt identification and timely treatment is essential for optimal and safe care of the patient. In this article, after presenting clinical cases we discuss the differing renal toxicity of three novel anticancer agents (aflibercept, dasatinib, and nivolumab) and possible measures to counter it.

Normal human macula densa morphology and cell turnover: A histological, ultrastructural, and immunohistochemical investigation.

The aim was to analyze the morphology of normal human macula densa (MD), evaluate the cells that may be responsible for its turnover, and collect quantitative data. Of four samples of normal human renal tissue, two were embedded in resin to measure the longitudinal extension and examine the ultrastructure of the MD, the other two were embedded in paraffin to study apoptosis and cell proliferation. The MD is composed of a monolayer tissue about 40 µm long, which includes 35-40 cells arranged in overlapping rows. Ultrastructurally, MD cells show two polarized portions: an apical end, with sensory features, and a basolateral aspect, with paracrine function. MD cells are connected apically by tight junctions, with/without adherens junctions, which form a barrier between the distal tubule lumen and the interstitium. Cells in degeneration, often associated with macrophages, and undifferentiated cells were found in the MD and adjacent distal tubule. A filamentous mat previously described in proximal tubule scattered tubular cells (STCs) was detected in the basal cytoplasm in undifferentiated cells. The tissue was consistently negative for the proliferation marker Ki67 and for the apoptotic markers caspase-3 and caspase-9. This work confirms our earlier morphological findings and provides new data: (a) MD cells display both apical adherens and tight junctions, the latter forming a tubulo-mesangial barrier; (b) the MD is a monolayer made up of about 40 cells arranged in rows; (c) the simultaneous presence of degenerating (8-13%) and undifferentiated (4-13%) cells reminiscent of STCs suggests a non-negligible cell turnover.

Two cases of microvillous inclusion disease caused by novel mutations in MYO5B gene.

Microvillous inclusion disease (MVID) typically appears with severe chronic diarrhea in the few days after birth and rapidly causes dehydration and metabolic acidosis. In this context, presenting two novel cases, we underline the crucial importance of mutation analysis for the diagnosis of this disease that may be easily misdiagnosed.

HtrA1 as a promising tissue marker in cancer: a meta-analysis.

BACKGROUND: HtrA1 is expressed in a variety of normal human tissues and seems to be involved in numerous physiological processes as well as tumorigenesis. This study reports the results of a meta-analysis that was performed: to compare HtrA1 expression as mRNA and protein, in cancer tissue versus non-cancer tissue and to assess overall survival in relation to low or medium-high HtrA1 tissue expression. METHODS: The PRISMA method was used for study selection. OR and HR with 95% confidence interval was used as a measure of effect size as appropriate. A random-effects model was applied to account for different sources of variation among studies. Heterogeneity across studies was assessed using Q statistic. Sensitivity analysis was conducted to check the stability of study findings. Egger's regression method was applied to test funnel plot asymmetry. RESULTS: Sensitivity analysis indicated the stability of meta-analytic findings in each meta-analysis. The study found a significantly different HtrA1 expression in cancer and non-cancer tissue. The meta-analysis of the prognostic studies showed a different survival according to HtrA1 expression. CONCLUSIONS: The present data may provide a contribution to future work directed at exploring the role of HtrA1 in tumor development and progression and at establishing whether it may be used as a promising tissue marker for some tumors.

Polarized Ends of Human Macula Densa Cells: Ultrastructural Investigation and Morphofunctional Correlations.

The morphology of the kidney macula densa (MD) has extensively been investigated in animals, whereas human studies are scanty. We studied the fine structure of human MD cells focusing on their apical and basal ends and correlating structure and function. The MD region was examined by transmission electron microscopy in six renal biopsies from patients with kidney disease. Ultrastructural analysis of MD cells was performed on serial sections. MD cells show two polarized ends. The apical portion is characterized by a single, immotile cilium associated with microvilli; apically, cells are joined by adhering junctions. In the basal portion, the cytoplasm contains small, dense granules and numerous, irregular cytoplasmic projections extending to the adjacent extraglomerular mesangium. The projections often contain small, dense granules. A reticulated basement membrane around MD cells separates them from the extraglomerular mesangium. Although the fact that tissue specimens came from patients with kidney disease mandates extreme caution, ultrastructural examination confirmed that MD cells have sensory features due to the presence of the primary cilium, that they are connected by apical adhering junctions forming a barrier that separates the tubular flow from the interstitium, and that they present numerous basal interdigitations surrounded by a reticulated basement membrane. Conceivably, the latter two features are related to the functional activity of the MD. The small, dense granules in the basal cytoplasm and in cytoplasmic projections are likely related to the paracrine function of MD cells. Anat Rec, 301:922-931, 2018. © 2017 Wiley Periodicals, Inc.

Effect of omiganan on colonic anastomosis healing in a rat model of peritonitis.

BACKGROUND: This study investigates the effects of the antimicrobial cationic peptide omiganan-alone and combined with the antibiotic imipenem-on colonic anastomosis healing in presence of intraperitoneal sepsis induced in a rodent model of cecal ligation and puncture (CLP). METHODS: Forty male Wistar rats were divided into 5 groups of 8 animals. Group 1 (control group) underwent laparotomy and cecal mobilization and the next day received left colon anastomosis. In group 2 (CLP without treatment), group 3 (CLP + imipenem), group 4 (CLP + omiganan), and group 5 (CLP + omiganan + imipenem), the left colon anastomosis was performed the day after CLP. Imipenem and omiganan were administered by intraperitoneal injection immediately before anastomosis construction and subsequently at 24 h intervals until the 7th postoperative day, when rats were sacrificed. Anastomotic bursting pressure was measured in situ. Tissue samples were collected for determination of hydroxyproline content and histological characteristics. RESULTS: Only rats receiving omiganan + imipenem displayed re-epithelialization, reduced neovascularization of granulation tissue, and a bursting pressure that was similar to that of controls. Omiganan-alone and combined with imipenem-was associated with a better control of inflammatory parameters than imipenem alone. In addition omiganan, like imipenem, counteracted the collagen depletion typical of sepsis. CONCLUSIONS: This experimental study demonstrates the efficacy of the new antimicrobial agent omiganan, alone and in combination with imipenem, in delaying the effects of intraperitoneal sepsis on colonic anastomosis healing and provides evidence of the value of omiganan as a therapeutic agent.

Low HtrA1 expression in patients with long­standing ulcerative colitis and colorectal cancer.

The association between inflammatory bowel disease (IBD) and colorectal cancer (CRC) is being increasingly investigated. HtrA1 overexpression inhibits cell growth and proliferation by influencing apoptosis, invasiveness and migration of tumour cells. In the present study, HtrA1 expression was analysed in 228 colon tissue samples from patients with CRC, adenoma with high-grade dysplasia (AHD), adenoma with low-grade dysplasia (ALD), ulcerative colitis of >10 year duration (UCL), ulcerative colitis of <5 year duration (UCS) and colonic diverticulitis (D), and was compared with its expression in normal colon tissues (NCTs) collected 5 cm from the CRC lesion and in healthy colon mucosa (HC), to establish whether HtrA1 can serve as a biomarker for these conditions. All tissue specimens came from Italian Caucasian subjects. The main finding of the present study was that HtrA1 expression was significantly reduced in CRC and UCL tissues compared with that observed in both NCT and HC samples and with tissues from the other patients. In particular, a similar HtrA1 expression was detected in the stromal compartment of UCL and CRC samples. In contrast, the HtrA1 level was significantly lower (p=0.0008) in UCL compared with UCS tissues, suggesting an inverse relationship between HtrA1 expression and ulcerative colitis duration. HtrA1 immunostaining in the stromal compartment of AHD and ALD tissues showed no differences compared with the HC tissues. No data are available on the immunohistochemical localization of HtrA1 in CRC or IBD. The present findings suggest that HtrA1 could serve as a marker to identify UCL patients at high risk of developing CRC.

CADASIL: Ultrastructural insights into the morphology of granular osmiophilic material.

INTRODUCTION: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a hereditary systemic vascular disorder. Granular osmiophilic material (GOM) is its ultrastructural marker. We reviewed tissue biopsies from CADASIL patients to establish whether ultrastructural observations help clarify the pathogenic mechanism of CADASIL. Given the resemblance of the GOM deposits to the immunoglobulin deposits seen in glomerulonephritis and focal segmental glomerulosclerosis (FSGS), their morphologies were investigated and compared. METHODS: Skin, skeletal muscle, kidney, and pericardium tissue biopsies from 13 patients with a clinical and molecular diagnosis of CADASIL, and kidney biopsies from five patients with IgA nephropathy and five patients with primary FSGS were subjected to ultrastructural examination. RESULTS: In CADASIL patients, several GOM deposits from all sites were partially or totally surrounded by an electron-lucent halo. The deposits frequently had a more electron-dense portion with a regular outline on the inner side and a less osmiophilic, looser outer side displaying a less regular profile. The uniformly dense deposits tended to be more osmiophilic if located close to the cell membrane and less osmiophilic if laid farther away from it. The immunoglobulin deposits from the glomerulonephritis and FSGS patients lacked both the granular pattern and the halo. CONCLUSIONS: This study demonstrates that GOM deposits may have a nonuniform morphology and describes in detail an electron-lucent halo surrounding several of them. It is conceivable that the halo is the morphological evidence and possibly the cause of an aberrant NOTCH3 processing, already suspected to be involved in CADASIL.