Overexpression of cyclin D1 in the Dami megakaryocytic cell line causes growth arrest

The maturation of megakaryocytes in vivo requires polyploidization or repeated duplication of DNA without cytokinesis. As DNA replication and cytokinesis are tightly regulated in somatic cells by cyclins and cyclin-dependent kinases, we sought to determine the pattern of cyclin gene expression in cells that undergo megakaryocytic differentiation and polyploidization. The Dami megakaryocytic cell line differentiates and increases ploidy in response to phorbol 12-myristate 13-acetate (PMA) stimulation in vitro. We used Northern blotting to analyze mRNA levels of cyclins A, B, C, D1, and E in PMA-induced Dami cells and found that cyclin D1 mRNA levels increased dramatically (18-fold). Similar increases in cyclin D1 mRNA were obtained for other cell lines (HEL and K562) with megakaryocytic properties, but not in HeLa cells. The increase in cyclin D1 was confirmed by Western immunoblotting of PMA-treated Dami cells. This finding suggested that cyclin D1 might participate in megakaryocyte differentiation by promoting endomitosis and/or inhibiting cell division. To address these possibilities, we constructed two stable Zn+2-inducible, cyclin D1-overexpressing Dami cell lines. Cyclin D1 expression alone was not sufficient to induce polyploidy, but in conjunction with PMA-induced differentiation, polyploidization was slightly enhanced. However, unlike other cell systems, cyclin D1 overexpression caused cessation of cell growth. Although the mechanism by which cyclin D1 may affect megakaryocyte differentiation is not clear, these data demonstrate that cyclin D1 is upregulated in differentiating megakaryocytic cells and may contribute to differentiation by arresting cell proliferation.     

Hazardous drinking is associated with an elevated aspartate aminotransferase to platelet ratio index in an urban HIV-infected clinical cohort

Objectives

The aim of the study was to determine the relationship between alcohol consumption and liver fibrosis as assessed by aspartate aminotransferase to platelet ratio index (APRI) in HIV‐infected adults and to explore the relative contributions of alcohol and hepatitis C virus (HCV) to APRI among HIV/HCV‐coinfected adults.

Methods

We performed a cross‐sectional analysis of data from an observational clinical cohort. Alcohol consumption was categorized according to National Institute on Alcohol Abuse and Alcoholism guidelines. We defined significant liver disease as APRI>1.5, and used multinomial logistic regression to identify correlates of increased APRI.

Results

Among 1358 participants, 10.4% reported hazardous drinking. It was found that 11.6% had APRI>1.5, indicating liver fibrosis. Hazardous drinking was associated with increased APRI [adjusted relative risk ratio (RRR) 2.30; 95% confidence interval (CI) 1.26–4.17]. Other factors associated with increased APRI were male gender, viral hepatitis, and HIV transmission category of injecting drug use. Among coinfected individuals, 18.3% had APRI>1.5, and hazardous drinking was not associated with APRI. Among non‐HCV‐infected individuals, 5.3% had APRI>1.5 and hazardous drinking was associated with increased APRI (adjusted RRR 3.72; 95% CI 1.40–9.87).

Conclusions

Hazardous drinking is an important modifiable risk factor for liver fibrosis, particularly among non‐HCV‐infected patients. Clinicians and researchers must address alcohol use as the burden of liver disease increases among HIV‐positive individuals.     

Association of HLA-DR with susceptibility to and clinical expression of rheumatoid arthritis: re-evaluation by means of genomic tissue typing

The clinical expression of rheumatoid arthritis (RA) varies considerably among individual patients. Genetic variations in human leucocyte antigen (HLA) may influence clinical expression. We re- examined the association of HLA-DR with susceptibility to and clinical expression of RA using genomic tissue typing, since most studies were based on (less reliable) serological techniques. Seventy-eight patients with recent-onset RA, all participating in a clinical trial on therapeutic strategies, were HLA-DR typed by means of low-resolution genomic typing. Cumulative disease activity within the first 3 yr of disease was measured. Of the RA patients, 54% expressed DR4 (DR4+) vs 26% of healthy controls. Rheumatoid factor (RF)-positive patients had a higher cumulative disease activity than RF-negative patients. Patients who were either DR1+ or DR4+ had a higher cumulative disease activity than those who expressed neither DR1 nor DR4. This association was less obvious after correction for RF status. The association of DR52+ (DR3, 5, 6) and a lower cumulative disease activity could also not be demonstrated after correction for RF status. Among RF-negative patients, DR51+ (or DR2+) was associated with a higher cumulative disease activity. Other HLA-DR types (including DR1 and DR4 separately) were not associated with the severity of RA. DR4 was associated with susceptibility to RA in our patients; HLA-DR low-resolution genomic tissue typing did not yield additional information to RF status for the clinical identification of individual patients with a poor prognosis.