Expression of Regulatory Platelet MicroRNAs in Patients with Sickle Cell Disease

Background: Increased platelet activation in sickle cell disease (SCD) contributes to a state of hypercoagulability and confers a risk of thromboembolic complications. The role for post-transcriptional regulation of the platelet transcriptome by microRNAs (miRNAs) in SCD has not been previously explored. This is the first study to determine whether platelets from SCD exhibit an altered miRNA expression profile. Methods and Findings: We analyzed the expression of miRNAs isolated from platelets from a primary cohort (SCD = 19, controls = 10) and a validation cohort (SCD = 7, controls = 7) by hybridizing to the Agilent miRNA microarrays. A dramatic difference in miRNA expression profiles between patients and controls was noted in both cohorts separately. A total of 40 differentially expressed platelet miRNAs were identified as common in both cohorts (p-value 0.05, fold change>2) with 24 miRNAs downregulated. Interestingly, 14 of the 24 downregulated miRNAs were members of three families - miR-329, miR-376 and miR-154 - which localized to the epigenetically regulated, maternally imprinted chromosome 14q32 region. We validated the downregulated miRNAs, miR-376a and miR-409-3p, and an upregulated miR-1225-3p using qRT-PCR. Over-expression of the miR-1225-3p in the Meg01 cells was followed by mRNA expression profiling to identify mRNA targets. This resulted in significant transcriptional repression of 1605 transcripts. A combinatorial approach using Meg01 mRNA expression profiles following miR-1225-3p overexpression, a computational prediction analysis of miRNA target sequences and a previously published set of differentially expressed platelet transcripts from SCD patients, identified three novel platelet mRNA targets: PBXIP1, PLAGL2 and PHF20L1. Conclusions: We have identified significant differences in functionally active platelet miRNAs in patients with SCD as compared to controls. These data provide an important inventory of differentially expressed miRNAs in SCD patients and an experimental framework for future studies of miRNAs as regulators of biological pathways in platelets. © 2013 Jain et al

MicroRNA-96 Directly Inhibits γ-Globin Expression in Human Erythropoiesis

Fetal hemoglobin, HbF (α2γ2), is the main hemoglobin synthesized up to birth, but it subsequently declines and adult hemoglobin, HbA (α2β2), becomes predominant. Several studies have indicated that expression of the HbF subunit γ-globin might be regulated post-transcriptionally. This could be confered by ∼22-nucleotide long microRNAs that associate with argonaute proteins to specifically target γ-globin mRNAs and inhibit protein expression. Indeed, applying immunopurifications, we found that γ-globin mRNA was associated with argonaute 2 isolated from reticulocytes that contain low levels of HbF (<1%), whereas association was significantly lower in reticulocytes with high levels of HbF (90%). Comparing microRNA expression in reticulocytes from cord blood and adult blood, we identified several miRNAs that were preferentially expressed in adults, among them miRNA-96. The overexpression of microRNA-96 in human ex vivo erythropoiesis decreased γ-globin expression by 50%, whereas the knock-down of endogenous microRNA-96 increased γ-globin expression by 20%. Moreover, luciferase reporter assays showed that microRNA-96 negatively regulates expression of γ-globin in HEK293 cells, which depends on a seedless but highly complementary target site located within the coding sequence of γ-globin. Based on these results we conclude that microRNA-96 directly suppresses γ-globin expression and thus contributes to HbF regulation

Racial differences in human platelet PAR4 reactivity reflect expression of PCTP and miR-376c.

Racial differences in the pathophysiology of atherothrombosis are poorly understood. We explored the function and transcriptome of platelets in healthy black (n = 70) and white (n = 84) subjects. Platelet aggregation and calcium mobilization induced by the PAR4 thrombin receptor were significantly greater in black subjects. Numerous differentially expressed RNAs were associated with both race and PAR4 reactivity, including PCTP (encoding phosphatidylcholine transfer protein), and platelets from black subjects expressed higher levels of PC-TP protein. PC-TP inhibition or depletion blocked PAR4- but not PAR1-mediated activation of platelets and megakaryocytic cell lines. miR-376c levels were differentially expressed by race and PAR4 reactivity and were inversely correlated with PCTP mRNA levels, PC-TP protein levels and PAR4 reactivity. miR-376c regulated the expression of PC-TP in human megakaryocytes. A disproportionately high number of microRNAs that were differentially expressed by race and PAR4 reactivity, including miR-376c, are encoded in the DLK1-DIO3 locus and were expressed at lower levels in platelets from black subjects. These results suggest that PC-TP contributes to the racial difference in PAR4-mediated platelet activation, indicate a genomic contribution to platelet function that differs by race and emphasize a need to consider the effects of race when developing anti-thrombotic drugs

Analysis of CYP1B1 sequence alterations in patients with primary open-angle glaucoma of Saudi origin

Khaled K Abu-Amero, Tahira Sultan, Saleh A Al-Obeidan, Altaf A Kondkar Glaucoma Research Chair, Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia Abstract: Cytochrome P450 Family 1 Subfamily B Member 1 (CYP1B1; OMIM# 601771) gene encodes one of the cytochrome P450 family of enzymes. CYP1B1 mutations have been associated primarily with primary congenital glaucoma (PCG). Similar studies were reported in juvenile open-angle glaucoma, Rieger&rsquo;s and Peters anomalies. Reports of likely pathogenic sequence alterations in families affected with adult-onset primary open-angle glaucoma (POAG) triggered this investigation. We screened unrelated POAG cases and healthy controls for mutations in CYP1B1 using automated Sanger sequencing to identify five known polymorphisms and one CYP1B1 mutation (p.G61E) in a heterozygous status. The p.G61E mutation is known to cause PCG in a homozygous or compound heterozygous form, and thus, its presence here in a heterozygous form indicates carrier status. These findings suggest that CYP1B1 may have no major role in the pathogenesis of POAG, at least, in the Saudi population. However, further investigations are needed to validate these findings in a larger cohort. Keywords: CYP1B1, genetics, mutation screening, POAG, Saudi Arabi

Elevated levels of plasma tumor necrosis factor alpha in patients with pseudoexfoliation glaucoma

Altaf A Kondkar,1 Taif A Azad,1 Faisal A Almobarak,1 Hatem Kalantan,1 Saleh A Al-Obeidan,1 Khaled K Abu-Amero1,2 1Glaucoma Research Chair, Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia; 2Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, USA Background: Tumor necrosis factor alpha (TNF-&alpha;) is a pro-inflammatory cytokine, which plays a role in glaucomatous neurodegeneration. Based on the plausible role of inflammation in the pathogenesis of pseudoexfoliation glaucoma (PEG), we investigated whether there is any relationship between the levels of plasma TNF-&alpha; and PEG or any of its clinical indices in comparison to normal controls.Methods: The study was designed as a retrospective analysis. Plasma samples from 49 PEG patients and 88 non-glaucomatous controls were evaluated for TNF-&alpha; levels using an enzyme-linked immunosorbent assay (ELISA). The assay was performed in duplicates on a biochemical/ELISA analyzer.Results: The two study groups were similar in age, sex and systemic disease distribution. The mean TNF-&alpha; concentration was significantly higher in the PEG patients (5.54&plusmn;4.58 pg/mL) than in the control subjects (0.93&plusmn;1.49 pg/mL; 95% confidence interval [CI] =3.50&ndash;5.72; p=0.000). The overall dose&ndash;response trend was significant (&chi;2=57.07, df=2; p=0.000). A moderate positive and significant correlation was seen between TNF-&alpha; level and cup/disc ratio, an important clinical index for PEG. Besides, binary logistic regression analysis showed that the risk of PEG was most significantly affected by TNF-&alpha; level as compared to no association with age and sex. In receiver operating characteristic analysis, the area under the curve was 0.777 (95% CI =0.682&ndash;0.872) and statistically significant (p=0.000).Conclusion: Elevated systemic levels of inflammatory marker, TNF-&alpha;, are associated with PEG and may possibly serve as a biomarker for undiagnosed early glaucoma and/or as a marker for disease progression. Keywords: glaucoma, inflammation, oxidative stress, pseudoexfoliation, TNF-&alpha

Association of increased levels of plasma tumor necrosis factor alpha with primary open-angle glaucoma

Altaf A Kondkar, Tahira Sultan, Faisal A Almobarak, Hatem Kalantan, Saleh A Al-Obeidan, Khaled K Abu-Amero Glaucoma Research Chair, Department of Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia Purpose: Retinal ganglion cell (RGC) death is a key feature of glaucoma. Elevated levels of tumor necrosis factor alpha (TNF-&alpha;), a pro-inflammatory cytokine, can induce RGC apoptosis and play a critical role in glaucomatous neurodegeneration. Based on the possible role of inflammation and oxidative stress in the pathogenesis of primary open-angle glaucoma (POAG), we investigated the association between plasma levels of TNF-&alpha; and POAG or its clinical indices in comparison to non-glaucomatous controls. Patients and methods: In a case&ndash;control retrospective cohort of 51 POAG cases and 88 controls, plasma TNF-&alpha; levels were measured using an enzyme-linked immunosorbent assay (ELISA). The assay was performed in duplicates on an automated ELISA analyzer. Results: Mean TNF-&alpha; level was significantly elevated in POAG cases (1.88 &plusmn; 2.17 pg/mL) than the controls (0.93 &plusmn; 1.49 pg/mL; p = 0.003). The overall dose&ndash;response trend was significant (&Chi;2 = 6.12, df = 2; p = 0.047). No statistical difference was seen in age, gender and systemic disease distribution. A modest negative and significant correlation was seen between TNF-&alpha; level and number of antiglaucoma medications, an important clinical index of POAG severity. Moreover, logistic regression analysis showed that the risk of POAG was most significantly affected by TNF-&alpha; level and not by age and sex. Conclusion: High systemic level of an inflammatory cytokine, TNF-&alpha;, is associated with POAG; however, its possible use as a biomarker for early glaucoma diagnosis and/or disease severity needs further investigation. Keywords: apoptosis, biomarker, cytokines, ELISA, inflammation, neurodegeneration, oxidative stres