Donny L.F. Chang

Interleukin-1β and Tumor Necrosis Factor-α Decrease Collagen Synthesis and Increase Matrix Metalloproteinase Activity in Cardiac Fibroblasts In Vitro

Abstract—We tested the hypothesis that the inflammatory cytokines can regulate fibroblast extracellular matrix metabolism. Neonatal and adult rat cardiac fibroblasts cultures in vitro were exposed to interleukin (IL)–1β (4 ng/mL), tumor necrosis factor-α (TNF-α; 100 ng/mL), IL-6 (10 ng/mL), or interferon-γ (IFN-γ; 500 U/mL) for 24 hours. IL-1β, and to a lesser extent TNF-α, decreased collagen synthesis, which was measured as collagenase-sensitive [3H]proline incorporation, but had no effect on cell number or total protein synthesis. IL-1β decreased the expression of procollagen α1(I), α2(I), and α1(III) mRNA, but increased the expression of procollagen α1(IV), α2(IV), and fibronectin mRNA, indicating a selective transcriptional downregulation of fibrillar collagen synthesis. IL-1β and TNF-α each increased total matrix metalloproteinase (MMP) activity as measured by in-gel zymography, causing specific increases in the bands corresponding to MMP-13, MMP-2, and MMP-9. IL-1β increased the expression of proMMP...

Inhibition of Copper-Zinc Superoxide Dismutase Induces Cell Growth, Hypertrophic Phenotype, and Apoptosis in Neonatal Rat Cardiac Myocytes In Vitro

Oxidative stress has been implicated in the pathophysiology of myocardial failure. We tested the hypothesis that inhibition of endogenous antioxidant enzymes can regulate the phenotype of cardiac myocytes. Neonatal rat ventricular myocytes in vitro were exposed to diethyldithiocarbamic acid (DDC), an inhibitor of cytosolic (Cu, Zn) and extracellular superoxide dismutase (SOD). DDC inhibited SOD activity and increased intracellular superoxide in a concentration-dependent manner. A low concentration (1 micromol/L) of DDC stimulated myocyte growth, as demonstrated by increases in protein synthesis, cellular protein, prepro-atrial natriuretic peptide, and c-fos mRNAs and decreased sarcoplasmic reticulum Ca(2+)ATPase mRNA. These actions were all inhibited by the superoxide scavenger Tiron (4,5-dihydroxy-1,3-benzene disulfonic acid). Higher concentrations of DDC (100 micromol/L) stimulated myocyte apoptosis, as evidenced by DNA laddering, characteristic nuclear morphology, in situ terminal deoxynucleotidyl transferase-mediated nick end-labeling (TUNEL), and increased bax mRNA expression. DDC-stimulated apoptosis was inhibited by the SOD/catalase mimetic EUK-8. The growth and apoptotic effects of DDC were mimicked by superoxide generation with xanthine plus xanthine oxidase. Thus, increased intracellular superoxide resulting from inhibition of SOD causes activation of a growth program and apoptosis in cardiac myocytes. These findings support a role for oxidative stress in the pathogenesis of myocardial remodeling and failure.

Oncogenic Signaling Pathways Activated in DMBA-Induced Mouse Mammary Tumors

Only about 5% of human breast cancers can be attributed to inheritance of breast cancer susceptibility genes, while the balance are considered to be sporadic in origin. Breast cancer incidence varies with diet and other environmental influences, including carcinogen exposure. However, the effects of environmental carcinogens on cell growth control pathways are poorly understood. Here we have examined oncogenic signaling pathways that are activated in mammary tumors in mice treated with the prototypical polycyclic aromatic hydrocarbon (PAH) 7,12-dimethylbenz[a]anthracene (DMBA). In female FVB mice given 6 doses of 1 mg of DMBA by weekly gavage beginning at 5 weeks of age, all of the mice developed tumors by 34 weeks of age (median 20 weeks after beginning DMBA); 75% of the mice had mammary tumors. DMBA-induced mammary tumors exhibited elevated expression of the aryl hydrocarbon receptor (AhR), c-myc, cyclin D1, and hyperphosphorylated retinoblastoma (Rb) protein. Because of this, the activation of upstream regulatory pathways was assessed, and elements of the Wnt signaling pathway, the NF-κB pathway, and the prolyl isomerase Pin-1 were found to be frequently up-regulated in the tumors when compared to normal mammary gland controls. These data suggest that environmental carcinogens can produce long-lasting alterations in growth and anti-apoptotic pathways, leading to mammary tumorigenesis.

Thyroid Testing during Pregnancy at an Academic Boston Area Medical Center

CONTEXT Gestational hypothyroidism leads to adverse obstetric outcomes and intellectual impairment in offspring. Pregnancy thyroid screening is controversial. OBJECTIVE Our objective was to determine thyroid function testing and thyroid dysfunction rates in pregnant women at Boston Medical Center (BMC). METHODS We retrospectively enrolled 1000 pregnant women aged 18-46 yr seen in BMCs Obstetrics/Gynecology (OB/GYN) or Family Medicine (FM) Clinics for their initial prenatal visit during 2008. Age, race, insurance, gestational age (GA), medical history (thyroid or other autoimmune disorders), obstetric history, and thyroid function tests were ascertained. RESULTS A total of 983 women were included (17 excluded for coding error). Median maternal age was 28 yr and GA 9.4 wk. Thyroid testing rates were similar in the 918 (93%) followed by OB/GYN and 65 (7%) followed by FM (84 vs. 86%). Thirty-nine women had previous thyroid disease, of whom 19 took thyroid medications. Four had type 1 diabetes, and nine had other autoimmune diseases. Serum TSH was obtained in 832 women (84.6%) at median GA 9.7 wk (range, 0.1-39.7). The majority were tested during their first trimester (65.5%). Of the 832 tested, 56 (6.7%) had trimester-specific elevated TSH, of whom nine had a previous history of thyroid disease, two had type 1 diabetes, and one had dyschromia. Based on current case-finding guidelines, 45 of 56 women (80.4%) with an elevated TSH in pregnancy might not have been tested. CONCLUSION BMC has a high rate of thyroid function testing in pregnancy. Targeted thyroid testing in only high-risk patients would have missed 80.4% of pregnant women with hypothyroidism.

DNA-binding and transactivation activities are essential for TAp63 protein degradation.

ABSTRACT The p53-related p63 gene encodes six isoforms with differing N and C termini. TAp63 isoforms possess a transactivation domain at the N terminus and are able to transactivate a set of genes, including some targets downstream of p53. Accumulating evidence indicates that TAp63 plays an important role in regulation of cell proliferation, differentiation, and apoptosis, whereas transactivation-inert ΔNp63 functions to inhibit p63 and other p53 family members. Mutations in the p63 gene that abolish p63 DNA-binding and transactivation activities cause human diseases, including ectrodactyly ectodermal dysplasia and facial clefting (EEC) syndrome. In this study, we show that mutant p63 proteins with a single amino acid substitution found in EEC syndrome are DNA binding deficient, transactivation inert, and highly stable. We demonstrate that TAp63 protein expression is tightly controlled by its specific DNA-binding and transactivation activities and that p63 is degraded in a proteasome-dependent, MDM2-independent pathway. In addition, the N-terminal transactivation domain of p63 is indispensable for its protein degradation. Furthermore, the wild-type TAp63γ can act in trans to promote degradation of mutant TAp63γ defective in DNA binding, and the TA domain deletion mutant of TAp63γ inhibits transactivation activity and stabilizes the wild-type TAp63 protein. Taken together, these data suggest a feedback loop for p63 regulation, analogous to the p53-MDM2 feedback loop.

Screening for Maternal Thyroid Dysfunction in Pregnancy: A Review of the Clinical Evidence and Current Guidelines

Observational studies have demonstrated that maternal thyroid dysfunction and thyroid autoimmunity in pregnancy may be associated with adverse obstetric and fetal outcomes. Treatment of overt maternal hyperthyroidism and overt hypothyroidism clearly improves outcomes. To date there is limited evidence that levothyroxine treatment of pregnant women with subclinical hypothyroidism, isolated hypothyroxinemia, or thyroid autoimmunity is beneficial. Therefore, there is ongoing debate regarding the need for universal screening for thyroid dysfunction during pregnancy. Current guidelines differ; some recommend an aggressive case-finding approach, whereas others advocate testing only symptomatic women or those with a personal history of thyroid disease or other associated medical conditions.

ARF promotes accumulation of retinoblastoma protein through inhibition of MDM2.

The INK4a/ARF locus, encoding two tumor suppressor proteins, p16INK4a and p14ARF (ARF), plays key roles in many cellular processes including cell proliferation, apoptosis, cellular senescence and differentiation. Inactivation of INK4a/ARF is one of the most frequent events during human cancer development. Although p16INK4a is a critical component in retinoblastoma protein (Rb)-mediated growth regulatory pathway, p14ARF plays a pivotal role in the activation of p53 upon oncogenic stress signals. A body of evidence indicates that ARF also possesses growth suppression functions independent of p53, the mechanism of which is not well understood. We have recently shown that MDM2 interacts with Rb and promotes proteasome-dependent Rb degradation. In this study, we show that ARF disrupts MDM2–Rb interaction resulting in Rb accumulation. Wild-type ARF, but not ARF mutant defective in MDM2 interaction, stabilizes Rb and inhibits colony foci formation independent of p53. In addition, ablation of Rb impairs ARF function in growth suppression. Thus, this study demonstrates that ARF plays a direct role in regulation of Rb and suggests that inactivation of ARF may lead to defects in both p53 and Rb pathways in human cancer development.

Increased Intraocular Pressure and Hyperglycemic Level in Diabetic Patients

Purpose To determine whether hyperglycemic levels as determined from high hemoglobin A1c (HbA1c) levels influence intraocular pressure (IOP) in patients with non-proliferative diabetic retinopathy (NPDR). Methods A retrospective chart review was performed on subjects with a diagnosis of NPDR and a corresponding HbA1c level measured within 90 days before or after an IOP measurement over a two-year period. Exclusion criteria included a diagnosis of glaucoma or treatment with IOP lowering medications or oral or topical steroids. Results Using 14.5mmHg as a baseline mean value for IOP, 42 subjects had an IOP < 14.5mmHg and mean HbA1c of 8.1±1.1, while 72 subjects had an IOP ≥ 14.5mmHg and a mean HbA1c of 9.0±2.1. Although there was an overlap in the confidence intervals, a significant difference (P = 0.01) in the mean HbA1c level was observed in regression analysis between the two groups. Importantly, diabetic subjects with elevated HbA1c levels rarely (<1%) exhibited reduced IOP levels. Conclusions Diabetic subjects with elevated HbA1c levels exhibited significantly higher IOPs compared to those with lower HbA1c levels. Findings from this study indicate an association between hyperglycemia and elevated IOP and that poor glycemic control may contribute to increased IOP levels in long-term diabetic patients.