Enhancement of camptothecin-induced cytotoxicity with UCN-01 in breast cancer cells: abrogation of S/G2 arrest

Purpose: To determine the ability of UCN-01 to abrogate the cell cycle arrest induced by camptothecin (CPT) in tumor cells that lack p53 function, and therefore enhance the cytotoxicity of CPT in these cells in relation to normal cells with wild-type p53. Methods: The responses of MDA-MB-231 and GI 101A breast cancer cells were compared to those of normal bovine endothelial cells. Cytotoxicity was assessed by the MTT assay, and the resulting data were modeled using median-effect analysis. Inhibition of DNA synthesis was determined by loss of [³H]thymidine incorporation, and cell cycle status was determined by flow cytometric analysis of propidium-iodide-stained nuclei. Results: UCN-01, a specific inhibitor of protein kinase C (PKC) presently in clinical trials, abrogated CPT-induced activation of S and G₂ checkpoints in human MDA-MB-231 and GI 101A breast carcinoma cells, both of which are mutants for the p53 gene. This abrogation occurred with the use of sublethal doses (100 nM) of UCN-01 and correlated with the enhancement of CPT-induced cytotoxicity. Median-effect analysis showed that synergistic cytotoxic interactions existed between CPT and UCN-01 against these tumor cells. In normal cells, however, abrogation of the S phase arrest caused accumulation in G₀/G₁ phase, perhaps by the presence of wild-type p53 activity, with no change in CPT-induced cytotoxicity. Conclusion: We have shown previously that the cytotoxicity of CPT is correlated with cell cycle response in normal and tumor cells. Low doses of CPT arrest cells in the G₂/M phase and inhibit DNA synthesis, but higher doses cause arrest of cells in S phase. Thus modulation of events at the S and G₂ checkpoints may provide an opportunity to enhance CPT-induced cytotoxicity in tumor cells. The results of this study indicate that UCN-01 enhances the progression of tumor cells through S phase thus greatly increasing CPT-induced cytotoxicity. Normal cells, however, are able to arrest in G₀/G₁ and thus avoid the increased toxicity induced by CPT. Our findings suggest potential usefulness of combining UCN-01 in topoisomerase I inhibitor-based drug therapy for the treatment of breast cancer with a dysfunctional p53 gene. Received: 25 February 1999 / Accepted: 4 October 1999     

Hyperglycemia and reactive oxygen species mediate apoptosis in aortic endothelial cells through Janus kinase 2

The generation of reactive oxygen species (ROS) has been implicated in the perturbation of endothelial function and cell death. However, the specific signaling pathways which mediate and modifying this response have not been fully elucidated. Therefore, in this study we tested the hypothesis that activation of JAK2 is involved in the aortic endothelial cell (EC) response to ROS. When ECs were exposed to HG (25 mM) for 6 h or ROS (i.e., H(2)O(2) (100 microM)) for 1 h and returned to normal medium we found a decrease in cell density and morphologic signs of apoptosis. Furthermore, incubation of ECs with HG and H(2)O(2) also resulted in the tyrosine phosphorylation of JAK2. In addition, pretreatment of ECs with AG-490, an inhibitor of JAK2, prevented nuclear fragmentation, whereas inhibitors of Jun kinase (SP 600125), MAP kinase (PD 98059), Src kinase (PP2) or PI-3 kinase (wortmannin) were without effect. Finally, immunoblot analysis of caspase-3 and PARP cleavage confirmed a role for activation of JAK2 in both HG- or ROS-induced apoptosis, based on inhibition by either AG-490 or adenoviral transfection with a dominant-negative JAK2 mutant. In conclusion the activation of JAK2 plays a pivotal role in oxidant stress-induced commitment of ECs to apoptosis, based on studies with HG and H(2)O(2).     

Acute renal failure in patients with ischemic heart disease: causes and novel approaches in breaking the cycle of self-perpetuating insults abrogated by surgery

At present, there seems to be diametrically opposing views on the causes of acute renal insufficiency in patients with ischemic heart disease (IHD) elective for cardiac revascularization. In this review, we examined recent advances in the understanding of the pathophysiology of acute renal failure in patients with IHD and surgery-induced acute phase reaction. Emphasis is given to the cellular and molecular mechanisms that contribute to the initiation and progression of inflammation. We evaluated the different pharmacological, technical, and surgical strategies used to improve the outcome of patients with IHD with impaired renal dysfunction and analyzed the influence of renal insufficiency on long-term results after surgery.     

Squamous Cell Carcinoma of the Prostate – A Case Report

Squamous cell carcinoma is a rare neoplasm of the prostate gland, forming about 0.5 of all prostatic malignancies. We present a case of squamous cell carcinoma of the prostate. Squamous cell carcinoma is usually indistinguishable from adenocarcinoma of the prostate by clinical features. Diagnosis is by histological examination. There are definite criteria for diagnosis like keratinisation, epithelial pearls and intercellular bridges. The cell of origin is widely accepted as the transitional epithelium of the urethra and periurethral ducts. This tumour is biologically much more aggressive than adenocarcinoma. There is no treatment modality which offers satisfactory results and the survival time is short.     

Resuscitation-induced gut edema and intestinal dysfunction

BACKGROUND: Mesenteric venous hypertension and subsequent gut edema play a pivotal role in the development of intra-abdominal hypertension. Although gut edema is one cause of intra-abdominal hypertension, its impact on gut function is unknown. The purpose of this study was to create a model of acute hydrostatic gut edema and to evaluate its effect on gut motility and barrier function. METHODS: The first study, group A, evaluated the effect of gut edema on transit over time using 20 mL/kg 0.9% saline. The second study, group B, focused on the 12-hour time period using 80 mL/kg 0.9% saline. Rats were randomized to superior mesenteric vein partial occlusion (venous hypertension) or sham surgery. At 6, 12, and 24 hours, group A underwent intestinal transit and tissue water weight measurements. At 12 hours, group B underwent tissue water, transit, ileal permeability and resistance, lactate and myeloperoxidase activity, and mucosal injury measurements. RESULTS: Venous hypertension with fluid resuscitation caused acute hydrostatic gut edema, delayed intestinal transit, increased mucosal permeability to macromolecules, and decreased tissue resistance over time. Mucosal injury was minimal in mesenteric venous hypertension. CONCLUSION: Acute mesenteric venous hypertension and resuscitation-induced gut edema, in the absence of ischemia/reperfusion injury, is associated with delayed intestinal transit and altered gut barrier function.     

Epidemiological aspects of prediabetes--review of the current data

The term 'prediabetes' has been used to describe the condition in which blood glucose levels are higher than normal but not yet diabetic and includes the two abnormalities, impaired glucose tolerance (IGT) and impaired fasting glucose (IFG). Subsequent to the American Diabetes Associaton (ADA) recommendation to adjust downward the normal fasting glucose level from 110 to 100 mg/dl, the prevalence of IFG has increased by 2 to 4 fold. The demonstration by recent randomised controlled trials that type 2 diabetes mellitus is preventable has raised hope for the possibility of reducing cardiovascular morbidity and mortality associated with diabetes. Interventions like lifestyle modification and pharmacological therapy are recommended in individuals with prediabetes to achieve the goal of prevention of diabetes in high -risk population.     

Unresolved priapism secondary to tamsulosin

Tamsulosin is the most potent adrenergic alpha-1 antagonist used for the treatment of benign prostatic hyperplasia. Priapism has been reported rarely in patients taking Prazosin, Doxazosin and Terazosin. We describe an otherwise healthy man with recurrent and then persistent unresolved priapism after the use of tamsulosin. Initial treatment consisted of aspiration and intracavernosal irrigation of iced saline and vasoconstrictive agent, but in vain. We then performed Winters procedure but that too failed and the priapism persisted. Health-care professionals should inform all patients taking such medications about rare but possible serious adverse effects.