Breast cancer metastatic potential correlates with a breakdown in homospecific and heterospecific gap junctional intercellular communication.

Breast cancer progresses toward increasingly malignant behavior in tumorigenic and metastatic stages. In the series of events in the metastatic stage, tumor cells leave the primary tumor in breast and travel to distant sites where they establish secondary tumors, or metastases. In this report, we demonstrate that cell-cell communication via gap junctions is restored in the metastatic human breast carcinoma cell line MDA-MB-435 when it is transfected with breast metastasis suppressor 1 (BRMS1) cDNA. Furthermore, the expression profile of connexins (Cxs), the protein subunits of gap junctions, changes. Specifically, the expression of BRMS1 in MDA-MB-435 cells increases Cx43 expression and reduces Cx32 expression, resulting in a gap junction phenotype more similar to normal breast tissue. Taken together, these results suggest that gap junctional communication and the Cx expression profile may contribute to the metastatic potential of these breast cancer cells.

Analysis of mechanisms underlying BRMS1 suppression of metastasis.

Introduction of normal, neomycin-tagged human chromosome 11 (neo11) reduces the metastatic capacity of MDA-MB-435 human breast carcinoma cells by 70-90% without affecting tumorigenicity. Differential display comparing MDA-MB-435 and neo11/435 led to the discovery of a human breast carcinoma metastasis suppressor gene, BRMS1, which maps to chromosome 11q13.1-q13.2. Stable transfectants of MDA-MB-435 and MDA-MB-231 breast carcinoma cells with BRMS1 cDNA still form progressively growing, locally invasive tumors when injected in mammary fat pads of athymic mice but exhibit significantly lower metastatic potential (50-90% inhibition) to lungs and regional lymph nodes. To begin elucidating the mechanism(s) of action, we measured the ability of BRMS1 to perturb individual steps of the metastatic cascade modeled in vitro. Consistent differences were not observed for adhesion to extracellular matrix components (laminin, fibronectin, type IV collagen, type I collagen, Matrigel); growth rates in vitro or in vivo; expression of matrix metalloproteinases, heparanase, or invasion. Likewise. BRMS1 expression did not up regulate expression of other metastasis suppressors, such as NM23, Kai1, KiSS1 or E-cadherin. Motility of BRMS1 transfectants was modestly inhibited (30-60%) compared to parental and vector-only transfectants. Ability to grow in soft agar was also decreased in MDA-MB-435 cells by 80-89%, but the decrease for MDA-MB-231 was less (13-15% reduction). Also, transfection and re-expression of BRMS1 restored the ability of human breast carcinoma cells to form functional homotypic gap junctions. Collectively, these data suggest that BRMS1 suppresses metastasis of human breast carcinoma by complex, atypical mechanisms.

Pretreatment with a nontoxic derivative of endotoxin induces functional protection against cardiac ischemia/reperfusion injury.

We hypothesized that low-dose pretreatment of an intact animal with a nontoxic derivative of endotoxin, monophosphoryl lipid A (MPL), would induce protection against cardiac ischemia/reperfusion (I/R) injury. The purposes of this study were to investigate whether MPL pretreatment would induce functional protection against cardiac I/R injury, to delineate the temporal induction of protection, and to examine antioxidant enzyme induction as a mechanism of protection. Rats were administered a 5 mg/kg dose of MPL at 2 hours and 24 hours before a 25-minute, global, 37 degrees C ischemic insult followed by reperfusion (modified Langendorff). At 40 minutes of reperfusion, ventricular function was assessed (ventricular balloon; developed pressure, rate of contraction, rate of relaxation). Hearts from rats pretreated with MPL 24 hours before isolation exhibited preservation of ventricular function (p less than 0.05). After I/R, hearts from rats pretreated with MPL 24 hours before isolation had increased (p less than 0.05) catalase activity compared to saline pretreated controls and rats pretreated with MPL 2 hours before isolation. We conclude that (1) pretreatment with MPL induces functional protection against cardiac I/R injury, (2) protection (not evident at 2 hours) is maximal at 24 hours, suggesting enzyme induction, and (3) increased catalase activity correlates with the functional protection.

Cardiac preconditioning does not require myocardial stunning.

Efforts to minimize the deleterious effects of intraoperative myocardial ischemia-reperfusion (I/R) injury have been primarily directed at optimizing cardioplegic solutions and altering reperfusion conditions. Classically, myocardial I/R has been associated with cardiac mechanical dysfunction ("stunning"). Recently, we reported an alpha 1-adrenergic receptor-mediated mechanism of paradoxical myocardial protection against I/R insult induced by a prior episode of transient ischemia, a phenomenon known as "ischemic preconditioning." Myocardial stunning resulting from transient ischemia has previously been associated with ischemic preconditioning, prompting intuitively negative bias against the clinical application of this phenomenon. The purpose of this study was to determine whether transient ischemia of insufficient duration to cause prolonged mechanical dysfunction (stunning) can induce favorable cardiac preconditioning. Isolated-perfused rat hearts were allowed to equilibrate for 8 minutes and were then subjected to either 2 minutes of global, normothermic transient ischemia or 2 minutes of 50 mumol/L phenylephrine infusion. A stabilization period of perfusion lasting 10 minutes after the termination of transient ischemia or phenylephrine infusion was followed by a standard I/R challenge (20 minutes of global, normothermic ischemia; 40 minutes of reperfusion). Ventricular function (measured as developed pressure in millimeters of mercury) recovered rapidly after transient ischemia such that no impairment was present before the subsequent standard I/R challenge. Phenylephrine treatment was associated with no residual inotropy before I/R challenge. Control hearts were subjected only to the standard I/R challenge after an initial 20-minute equilibration period. After reperfusion control hearts exhibited 54.4% recovery of initial left ventricular developed pressure. Transient ischemia- and phenylephrine-preconditioned hearts recovered 84.4% (p < 0.01) and 82.4% (p < 0.01), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

L-glutamate-induced changes in intracellular calcium oscillation frequency through non-classical glutamate receptor binding in cultured rat myocardial cells.

The effects of L-glutamate, N-methyl-D-aspartate (NMDA), kainate (KA) and L-alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionate (AMPA) on intracellular Ca2+ oscillation frequency were studied in cultured rat myocardial cells. Ca2+ oscillations per minute were increased as compared to control by L-glutamate (100 microM) from 3.8 +/- 2.2 to 25.7 +/- 4.3 (p < 0.001) and the NMDA-receptor agonist, NMDA (100 microM), from 1.2 +/- 0.8 to 34.8 +/- 10.1 (p < 0.011). Increases over control frequency were also seen in response to the non-NMDA receptor agonists KA (100 microM) from 5.8 +/- 2.3 to 25.6 +/- 3.2 (p < 0.001) and AMPA (10 microM) from 3.8 +/- 1.2 to 13.3 +/- 1.8 (p < 0.001). The non-competitive NMDA receptor antagonist, (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK801) (10 microM), decreased the Ca2+ oscillation frequency induced by NMDA (100 microM from 36.8 +/- 12.2 to 7.2 +/- 7.2 (p < 0.05). (+/-)-2-Amino-7-phosphonoheptanoic acid (AP7), a competitive inhibitor at the NMDA receptor inhibited the increase in frequency induced by KA (100 microM) at all concentrations tested (0.1, 1.0, 10 and 100 microM). 6,7-Dinitroquinoxaline-2,3-dione (DNQX), a competitive inhibitor at non-NMDA receptors, also decreased the oscillation frequency elicited by KA (100 microM) from 35.4 +/- 9.4 to 28.2 +/- 9.8, 24.8 +/- 9.8 and 11 +/- 9.5 at concentrations of 0.1, 1.0 and 10 microM respectively. The peak amount of intracellular Ca2+ as expressed as the fluo 3 ratio, F/Frcst, was not increased by L-glutamate, NMDA or KA. These results suggest the presence of a novel glutamate receptor composed of both non-NMDA and NMDA subunits on cultured rat myocardial cells, and receptor stimulation leads to an increase in intracellular Ca2+ oscillation frequency.

Psychosocial factors at work and musculoskeletal disease.

The objective of this review is to establish whether the epidemiologic literature presents evidence of an association between psychosocial work factors and musculoskeletal disease. In a hypothetical model it is suggested that individual characteristics and stress symptoms can modify this relationship. The reviewed studies do not present conclusive evidence due to high correlations between psychosocial factors and physical load and to difficulties in measuring dependent and independent variables. Nevertheless, it is concluded that monotonous work, high perceived work load, and time pressure are related to musculoskeletal symptoms. The data also suggest that low control on the job and lack of social support by colleagues are positively associated with musculoskeletal disease. Perceived stress may be an intermediary in this process. In addition, stress symptoms are often associated with musculoskeletal disease, and some studies indicate that stress symptoms contribute to the development of this disease.

Quality and effectiveness of occupational health service evaluated by the providers.

In a debate on the desired occupational health service in The Netherlands all parties involved seemed to be rather unsatisfied with current practice. Therefore a study was set out on the quality of the service to 51 client organizations as seen by the parties involved. In the first phase the viewpoint of the occupational health teams was studied; the second phase among clients was planned later. As it was not feasible to use proper measures of effectiveness, i.e. of outcome in terms of health, the interview was used as method directed at the evaluations of the teams themselves. It focused on the adequacy of the activities of the teams in view of the health problems and risks in the client organization and on the necessary interaction with the clients in order to reach effective service. Although a self-evaluation-method like this has its limitations, results are relevant for the debate on the quality of OHS in The Netherlands. Many occupational health teams want more capacity for preventive activities and to devote more time to these activities to enhance the quality of their service and be more effective. It is argued that for the same purpose the teams themselves should strive for good relations with their clients.