Posterior fossa volume in idiopathic intracranial hypertension: a magnetic resonance imaging-based study.

BACKGROUND: The etiology of idiopathic intracranial hypertension (IIH) is uncertain. Studies suggest the fundamental cause of the Chiari 1 malformation, a congenitally hypoplastic posterior fossa, may explain the genesis of IIH in some patients. PURPOSE: To assess the hypothesis that linear and volumetric measurements of the posterior fossa (PF) can be used as predictors of IIH. MATERIAL AND METHODS: A retrospective analysis of magnetic resonance imaging (MRI) studies on 27 patients with IIH and 14 matched controls was performed. A volumetric sagittal magnetization prepared rapid acquisition gradient echo sequence was used to derive 10 linear cephalometric measurements. Total intracranial and bony posterior fossa volumes (PFVs) were derived by manual segmentation. The ratio of PFV to total intracranial volume was calculated. RESULTS: In total, 41 participants were included, all women. Participants with IIH had higher median body mass index (BMI). No significant differences in linear cephalometric measurements, total intracranial volumes, and PFVs between the groups were identified. Linear measurements were not predictive of volumetric measurements. However, on multivariate logistic regression analysis, the likelihood of IIH decreased significantly per unit increase in relative PFV (odds ratio [OR]=3.66 × 10-50; 95% confidence interval [CI]=1.39 × 10-108 to 1.22 × 10-5; P = 0.04). Conversely, the likelihood of IIH increased per unit BMI increase (OR=1.19; 95% CI=1.04-1.47; P = 0.02). CONCLUSION: MRI-based volumetric measurements imply that PF alterations may be partly responsible for the development of IIH and Chiari 1 malformations. Symptoms of IIH may arise due to an interplay between these and metabolic, hormonal, or other factors.

Phosphorylated SIRT1 as a biomarker of relapse and response to treatment with glatiramer acetate in multiple sclerosis.

We have previously shown that SIRT1 mRNA expression was significantly lower in relapsing MS patients compared to those in remission. Our goal was to longitudinally investigate the role of active, phosphorylated SIRT1 (p-SIRT1) as a potential biomarker of relapse and predictor for response to glatiramer acetate (GA) treatment in patients with relapsing remitting multiple sclerosis (MS). We also want to investigate the downstream effects of SIRT1 activation by measuring the trimethylation of histone 3 at lysine 9 (H3K9me3). A cohort of 15 GA-treated patients was clinically monitored using the Expanded Disability Status Scale (EDSS) and peripheral blood mononuclear cells (PBMCs) were collected at 0, 3, 6, and 12 months after initiation of the therapy. P-SIRT1 and H3K9me3 levels were assayed by Western blotting using specific antibodies. Statistically significant lower levels of p-SIRT1 protein (p < 0.0001) and H3K9me3 (p = 0.001) were found during relapses when compared to stable MS patients. Non-responders to GA treatment were defined as patients who exhibited at least two relapses following initiation of GA treatment. Statistically significant lower levels of p-SIRT1 protein (p = 0.02) and H3K9me3 (p = 0.004) were found in GA non-responders compared to responders. Using receiver operating characteristic analysis, area under the curve (AUC) for p-SIRT1 was 77% (p = 0.007) and for H3K9me3 was 81% (p = 0.002) for prediction of relapse. For predicting responsiveness to GA treatment, AUC was 75% (P = 0.01) for H3K9me3. Our data suggest that p-SIRT1 and H3K9me3 could serve as potential biomarkers for MS relapse. In addition, H3K9me3 could serve as possible biomarker to predict response to GA treatment.

SIRT1 as a potential biomarker of response to treatment with glatiramer acetate in multiple sclerosis.

SIRT1, a NAD dependent histone and protein deacetylase, is a member of the histone deacetylase class III family. We previously showed that SIRT1 mRNA expression is significantly lower in peripheral blood mononuclear cells (PBMCs) of multiple sclerosis (MS) patients during relapses than in stable patients. We have now investigated SIRT1 as a possible biomarker to predict relapse as well as responsiveness to glatiramer acetate (GA) treatment in relapsing-remitting MS (RRMS) patients. Over the course of 2years, a cohort of 15 GA-treated RRMS patients were clinically monitored using the Expanded Disability Status Scale and assessed for MS relapses. Blood samples collected from MS patients were analyzed for levels of SIRT1 and histone H3 lysine 9 (H3K9) acetylation and dimethylation. During relapses, MS patients had a lower expression of SIRT1 mRNA than did stable MS patients. In addition, there was a significant decrease in H3K9 dimethylation (H3K9me2) during relapses in MS patients when compared to stable patients (p=0.01). Responders to GA treatment had significantly higher SIRT1 mRNA (p=0.01) and H3K9me2 levels than did non-responders (p=0.018). Receiver operating characteristic analysis was used to assess the predictive power of SIRT1 and H3K9me2 as putative biomarkers: for SIRT1 mRNA, the predictive value for responsiveness to GA treatment was 70% (p=0.04) and for H3K9me2 was 71% (p=0.03). Our data suggest that SIRT1 and H3K9me2 could serve as potential biomarkers for evaluating patients' responsiveness to GA therapy in order to help guide treatment decisions in MS.

RGC-32 is expressed in the human atherosclerotic arterial wall: Role in C5b-9-induced cell proliferation and migration.

The complement system is an important player in the development of atherosclerosis. Previously reported as a cell cycle regulator, RGC-32 is an essential effector of the terminal complement complex, C5b-9. In this study, our aims were to determine the expression of RGC-32 in the human atherosclerotic arterial wall and to delineate the mechanisms through which RGC-32 affects C5b-9-induced endothelial cell proliferation and migration. We now demonstrate that RGC-32 is expressed in human aortic atherosclerotic wall and that RGC-32 expression increases with the progression of atherosclerosis. Furthermore, silencing of RGC-32 expression abolished C5b-9-induced human aortic endothelial cell (HAEC) proliferation and migration. Of the 279 genes differentially expressed in HAECs after RGC-32 silencing, the genes involved in cell adhesion and cell cycle activation were significantly regulated by RGC-32. RGC-32 silencing caused a significant reduction in the expression of cyclin D1, cyclin D3, Akt, ROCK1, Rho GDP dissociation inhibitor alpha and profilin. These data suggest that RGC-32 mediates HAEC migration through the regulation of RhoA and ROCK1 expression and is involved in actin cytoskeletal organization. Thus, RGC-32 has promising therapeutic potential with regard to angiogenesis and atherosclerosis.

Melanosomal dynamics assessed with a live-cell fluorescent melanosomal marker.

Melanocytes present in skin and other organs synthesize and store melanin pigment within membrane-delimited organelles called melanosomes. Exposure of human skin to ultraviolet radiation (UV) stimulates melanin production in melanosomes, followed by transfer of melanosomes from melanocytes to neighboring keratinocytes. Melanosomal function is critical for protecting skin against UV radiation, but the mechanisms underlying melanosomal movement and transfer are not well understood. Here we report a novel fluorescent melanosomal marker, which we used to measure real-time melanosomal dynamics in live human epidermal melanocytes (HEMs) and transfer in melanocyte-keratinocyte co-cultures. A fluorescent fusion protein of Ocular Albinism 1 (OA1) localized to melanosomes in both B16-F1 cells and HEMs, and its expression did not significantly alter melanosomal distribution. Live-cell tracking of OA1-GFP-tagged melanosomes revealed a bimodal kinetic profile, with melanosomes exhibiting combinations of slow and fast movement. We also found that exposure to UV radiation increased the fraction of melanosomes exhibiting fast versus slow movement. In addition, using OA1-GFP in live co-cultures, we monitored melanosomal transfer using time-lapse microscopy. These results highlight OA1-GFP as a specific and effective melanosomal marker for live-cell studies, reveal new aspects of melanosomal dynamics and transfer, and are relevant to understanding the skin's physiological response to UV radiation.

UVA phototransduction drives early melanin synthesis in human melanocytes.

Exposure of human skin to solar ultraviolet radiation (UVR), a powerful carcinogen [1] comprising ~95% ultraviolet A (UVA) and ~5% ultraviolet B (UVB) at the Earth's surface, promotes melanin synthesis in epidermal melanocytes [2, 3], which protects skin from DNA damage [4, 5]. UVB causes DNA lesions [6] that lead to transcriptional activation of melanin-producing enzymes, resulting in delayed skin pigmentation within days [7]. In contrast, UVA causes primarily oxidative damage [8] and leads to immediate pigment darkening (IPD) within minutes, via an unknown mechanism [9, 10]. No receptor protein directly mediating phototransduction in skin has been identified. Here we demonstrate that exposure of primary human epidermal melanocytes (HEMs) to UVA causes calcium mobilization and early melanin synthesis. Calcium responses were abolished by treatment with G protein or phospholipase C (PLC) inhibitors or by depletion of intracellular calcium stores. We show that the visual photopigment rhodopsin [11] is expressed in HEMs and contributes to UVR phototransduction. Upon UVR exposure, significant melanin production was measured within one hour; cellular melanin continued to increase in a retinal- and calcium-dependent manner up to 5-fold after 24 hr. Our findings identify a novel UVA-sensitive signaling pathway in melanocytes that leads to calcium mobilization and melanin synthesis and may underlie the mechanism of IPD in human skin.