Faculty Bibliography

Aims: Glutathione (GSH) is the main antioxidant against cell damage. Several pathological states course with reduced nucleophilic tone and perturbation of redox homeostasis due to changes in the 2GSH/GSSG ratio. Here we investigated the regulation of the rate limiting GSH biosynthetic heterodimeric enzyme gamma-glutamate-cysteine- ligase (GCL) by microRNAs (miRNAs). Results: "In silico" analysis of the 3'-UTR regions of both catalytic (GCLc) and regulatory (GCLm) subunits of GCL, allowed to identify miR-433 as a strong candidate for the targeting of GCL. Transitory overexpression of miR-433 in HUVEC showed a downregulation of both GCLc and GCLm in a Nrf2-independent manner. Increases in pro-oxidant stimuli such as exposure to H2O2 or GSH depletion in endothelial and hepatic cells caused an expected increase in GCLc and GCLm protein expression and abrogation of miR-433 levels, thus supporting a cross-regulation of these pathways. Treatment of HUVEC with miR-433 resulted in reduced antioxidant and redox potentials, increased S-glutathionylation and reduced eNOS activation. In vivo models of renal and hepatic fibrosis were associated with transforming growth factor beta1 (TGF-beta1)-related reduction of GCLc and GCLm levels that were miR-433 dependent. Innovation and Conclusion: We describe for the first time a miRNA, miR-433, capable of directly targeting GCL and promoting functional consequences in endothelial physiology and fibrotic processes by decreasing GSH levels.

The cyclin-dependent kinase (CDK) inhibitor p27kip1 is a critical regulator of the G1/S-phase transition of the cell cycle and also regulates microtubule (MT) stability. This latter function is exerted by modulating the activity of stathmin, an MT-destabilizing protein, and by direct binding to MTs. We recently demonstrated that increased proliferation in p27kip1-null mice is reverted by concomitant deletion of stathmin in p27kip1/stathmin double-KO mice, suggesting that a CDK-independent function of p27kip1 contributes to the control of cell proliferation. Whether the regulation of MT stability by p27kip1 impinges on signaling pathway activation and contributes to the decision to enter the cell cycle is largely unknown. Here, we report that faster cell cycle entry of p27kip1-null cells was impaired by the concomitant deletion of stathmin. Using gene expression profiling coupled with bioinformatic analyses, we show that p27kip1 and stathmin conjunctly control activation of the MAPK pathway. From a molecular point of view, we observed that p27kip1, by controlling MT stability, impinges on H-Ras trafficking and ubiquitination levels, eventually restraining its full activation. Our study identifies a regulatory axis controlling the G1/S-phase transition, relying on the regulation of MT stability by p27kip1 and finely controlling the spatiotemporal activation of the Ras-MAPK signaling pathway.

During urinary tract infection (UTI), the second most common bacterial infection, dynamic interactions take place between uropathogenic E. coli (UPEC) and host urothelial cells. While significant strides have been made in the identification of the virulence factors of UPEC, our understanding of how the urothelial cells mobilize innate defenses against the invading UPEC remains rudimentary. Here we show that mouse urothelium responds to the adhesion of type 1-fimbriated UPEC by rapidly activating the canonical NF-kappaB selectively in terminally differentiated, superficial (umbrella) cells. This activation depends on a dual ligand/receptor system, one between FimH adhesin and uroplakin Ia and another between lipopolysaccharide and Toll-like receptor 4. When activated, all the nuclei (up to 11) of a multinucleated umbrella cell are affected, leading to significant amplification of proinflammatory signals. Intermediate and basal cells of the urothelium undergo NF-kappaB activation only if the umbrella cells are detached or if the UPEC persistently express type 1-fimbriae. Inhibition of NF-kappaB prevents the urothelium from clearing the intracellular bacterial communities, leading to prolonged bladder colonization by UPEC. Based on these data, we propose a model of dual ligand/receptor system in innate urothelial defenses against UPEC.

Dysregulation of amyloid-beta (Abeta) metabolism is critical for Alzheimer's disease (AD) pathogenesis. Mounting evidence suggests that apolipoprotein E (ApoE) is involved in Abeta metabolism. ATP-binding cassette transporter A1 (ABCA1) is a key regulator of ApoE lipidation, which affects Abeta levels. Therefore, identifying regulatory mechanisms of ABCA1 expression in the brain may provide new therapeutic targets for AD. Here, we demonstrate that microRNA-33 (miR-33) regulates ABCA1 and Abeta levels in the brain. Overexpression of miR-33 impaired cellular cholesterol efflux and dramatically increased extracellular Abeta levels by promoting Abeta secretion and impairing Abeta clearance in neural cells. In contrast, genetic deletion of mir-33 in mice dramatically increased ABCA1 levels and ApoE lipidation, but it decreased endogenous Abeta levels in cortex. Most importantly, pharmacological inhibition of miR-33 via antisense oligonucleotide specifically in the brain markedly decreased Abeta levels in cortex of APP/PS1 mice, representing a potential therapeutic strategy for AD. SIGNIFICANCE STATEMENT: Brain lipid metabolism, in particular Apolipoprotein E (ApoE) lipidation, is critical to Abeta metabolism and Alzheimer's disease (AD). Brain lipid metabolism is largely separated from the periphery due to blood-brain barrier and different repertoire of lipoproteins. Therefore, identifying the novel regulatory mechanism of brain lipid metabolism may provide a new therapeutic strategy for AD. Although there have been studies on brain lipid metabolism, its regulation, in particular by microRNAs, is relatively unknown. Here, we demonstrate that inhibition of microRNA-33 increases lipidation of brain ApoE and reduces Abeta levels by inducing ABCA1. We provide a unique approach for AD therapeutics to increase ApoE lipidation and reduce Abeta levels via pharmacological inhibition of microRNA in vivo.

PURPOSE: Brain metastasis is the major cause of mortality among melanoma patients. A molecular prognostic test that can reliably stratify patients at initial melanoma diagnosis by risk of developing brain metastasis may inform the clinical management of these patients. EXPERIMENTAL DESIGN: We performed a retrospective, cohort-based study analyzing genome-wide and targeted microRNA expression profiling of primary melanoma tumors of three patient cohorts (n= 92, n= 119, n= 45) with extensive clinical follow up. We used Cox regression analysis to establish a microRNA-based signature that improves the ability of the current clinicopathologic staging system to predict the development of brain metastasis. RESULTS: Our analyses identified a 4-microRNA (miR-150-5p, miR-15b-5p, miR-16-5p, and miR-374b-3p) prognostic signature that, in combination with stage, distinguished primary melanomas that metastasized to the brain from non-recurrent and non-brain-metastatic primary tumors (training cohort: C-index=81.4%, validation cohort: C-index=67.4%, independent cohort: C-index=76.9%). Corresponding Kaplan-Meier curves of high- vs. low-risk patients displayed a clear separation in brain-metastasis-free and overall survival (training: p<0.001, p<0.001, validation: p=0.033, p=0.007, independent: p=0.021, p=0.022, respectively). Finally, of the microRNA in the prognostic model, we found that the expression of a key lymphocyte miRNA, miR-150-5p, which is less abundant in primary melanomas metastatic to brain, correlated with presence of CD45+ tumor infiltrating lymphocytes. CONCLUSIONS: A prognostic assay based on the described miRNA expression signature combined with the currently used staging criteria may improve accuracy of primary melanoma patient prognoses and aid clinical management of patients, including selection for adjuvant treatment or clinical trials of adjuvant therapies.

Genome-wide association studies (GWASs) have linked genes to various pathological traits. However, the potential contribution of regulatory noncoding RNAs, such as microRNAs (miRNAs), to a genetic predisposition to pathological conditions has remained unclear. We leveraged GWAS meta-analysis data from >188,000 individuals to identify 69 miRNAs in physical proximity to single-nucleotide polymorphisms (SNPs) associated with abnormal levels of circulating lipids. Several of these miRNAs (miR-128-1, miR-148a, miR-130b, and miR-301b) control the expression of key proteins involved in cholesterol-lipoprotein trafficking, such as the low-density lipoprotein (LDL) receptor (LDLR) and the ATP-binding cassette A1 (ABCA1) cholesterol transporter. Consistent with human liver expression data and genetic links to abnormal blood lipid levels, overexpression and antisense targeting of miR-128-1 or miR-148a in high-fat diet-fed C57BL/6J and Apoe-null mice resulted in altered hepatic expression of proteins involved in lipid trafficking and metabolism, and in modulated levels of circulating lipoprotein-cholesterol and triglycerides. Taken together, these findings support the notion that altered expression of miRNAs may contribute to abnormal blood lipid levels, predisposing individuals to human cardiometabolic disorders.

PURPOSE: The effect of age on telomere length heterogeneity in men has not been studied previously. Our aims were to determine the relationship between variation in sperm telomere length (STL), men's age, and semen parameters in spermatozoa from men undergoing in vitro fertilization (IVF) treatment. METHODS: To perform this prospective cross-sectional pilot study, telomere length was estimated in 200 individual spermatozoa from men undergoing IVF treatment at the NYU Fertility Center. A novel single-cell telomere content assay (SCT-pqPCR) measured telomere length in individual spermatozoa. RESULTS: Telomere length among individual spermatozoa within an ejaculate varies markedly and increases with age. Older men not only have longer STL but also have more variable STL compared to younger men. STL from samples with normal semen parameters was significantly longer than that from samples with abnormal parameters, but STL did not differ between spermatozoa with normal versus abnormal morphology. CONCLUSION: The marked increase in STL heterogeneity as men age is consistent with a role for ALT during spermatogenesis. No data have yet reported the effect of age on STL heterogeneity. Based on these results, future studies should expand this modest sample size to search for molecular evidence of ALT in human testes during spermatogenesis.

Mutations in genes encoding Isocitrate Dehydrogenase (IDH) isoforms are found in80%of low-grade gliomas (LGGs). Sequencing of LGGs has revealed branching cancer genetics; mutant IDH1 astrocytomas contain p53 and ATRX loss of function mutations, while IDH1-mutated oligodendrogliomas have a different set of mutations that includes chr 1p/19q co-deletion. The IDH mutation is a gain-of-function change at its catalytic core that results in the production of (R)-2-hydroxyglutarate, an oncometabolite, which causes characteristic DNA and histone hypermethylation changes that may contribute to tumorigenesis. Mouse models have thus far failed to demonstrate the role of IDH1 mutations in LGG formation. To test the hypothesis that mutant IDH1 is a driver of gliomagenesis, we use human embryonic stem cell (hESC)-derived neural stem cells (NSCs) to overexpress mutant IDH1 protein in combination with p53 and ATRX knockdown. We have generated twelve NSC lines that harbor combinations of mutant IDH1, wt IDH1 or an empty vector, in combination with ATRX and/or p53 knockdown. Our preliminary data indicate that mutantIDH1 does not alter the proliferative capacity of NSCs, as shown by cell cycle analysis and Ki67 staining, but paradoxically increases their apoptotic rate (15.8% vs 5.9% n = 4), a phenotype that is exacerbated by ATRX knockdown, as detected by annexin V and TUNEL staining (17.7% vs 2.6% n = 3). shRNA-mediated knockdown of p53 salvages the pro-apoptotic phenotype of mutant IDH1 and ATRX NSCs. Furthermore, initial observations suggest that mutant IDH1 biases NSCs toward glial fates, as evidenced by upregulation of the CD44 cell surface marker. We are currently testing the effects of IDH1 mutation on i) NSC differentiation to astrocytic and neuronal lineages, ii) NSC metabolism via metabolomics profiling and iii) in vivo tumorigenesis. We propose that mutant IDH1 alters the differentiation program of human NSCs toward glial rather than neuronal fates