Spine degeneration in a murine model of chronic human tobacco smokers.

OBJECTIVE: To investigate the mechanisms by which chronic tobacco smoking promotes intervertebral disc degeneration (IDD) and vertebral degeneration in mice. METHODS: Three month old C57BL/6 mice were exposed to tobacco smoke by direct inhalation (4 cigarettes/day, 5 days/week for 6 months) to model long-term smoking in humans. Total disc proteoglycan (PG) content [1,9-dimethylmethylene blue (DMMB) assay], aggrecan proteolysis (immunobloting analysis), and cellular senescence (p16INK4a immunohistochemistry) were analyzed. PG and collagen syntheses ((35)S-sulfate and (3)H-proline incorporation, respectively) were measured using disc organotypic culture. Vertebral osteoporosity was measured by micro-computed tomography. RESULTS: Disc PG content of smoke-exposed mice was 63% of unexposed control, while new PG and collagen syntheses were 59% and 41% of those of untreated mice, respectively. Exposure to tobacco smoke dramatically increased metalloproteinase-mediated proteolysis of disc aggrecan within its interglobular domain (IGD). Cellular senescence was elevated two-fold in discs of smoke-exposed mice. Smoke exposure increased vertebral endplate porosity, which closely correlates with IDD in humans. CONCLUSIONS: These findings further support tobacco smoke as a contributor to spinal degeneration. Furthermore, the data provide a novel mechanistic insight, indicating that smoking-induced IDD is a result of both reduced PG synthesis and increased degradation of a key disc extracellular matrix protein, aggrecan. Cleavage of aggrecan IGD is extremely detrimental as this results in the loss of the entire glycosaminoglycan-attachment region of aggrecan, which is vital for attracting water necessary to counteract compressive forces. Our results suggest identification and inhibition of specific metalloproteinases responsible for smoke-induced aggrecanolysis as a potential therapeutic strategy to treat IDD.

K-ras activation generates an inflammatory response in lung tumors.

Activating mutations in K-ras are one of the most common genetic alterations in human lung cancer. To dissect the role of K-ras activation in bronchial epithelial cells during lung tumorigenesis, we created a model of lung adenocarcinoma by generating a conditional mutant mouse with both Clara cell secretory protein (CC10)-Cre recombinase and the Lox-Stop-Lox K-ras(G12D) alleles. The activation of K-ras mutant allele in CC10 positive cells resulted in a progressive phenotype characterized by cellular atypia, adenoma and ultimately adenocarcinoma. Surprisingly, K-ras activation in the bronchiolar epithelium is associated with a robust inflammatory response characterized by an abundant infiltration of alveolar macrophages and neutrophils. These mice displayed early mortality in the setting of this pulmonary inflammatory response with a median survival of 8 weeks. Bronchoalveolar lavage fluid from these mutant mice contained the MIP-2, KC, MCP-1 and LIX chemokines that increased significantly with age. Cell lines derived from these tumors directly produced MIP-2, LIX and KC. This model demonstrates that K-ras activation in the lung induces the elaboration of inflammatory chemokines and provides an excellent means to further study the complex interactions between inflammatory cells, chemokines and tumor progression.

Vitamin D receptor and growth inhibition by 1,25-dihydroxyvitamin D3 in human malignant melanoma cell lines.

The expression of vitamin D receptors (VDR) and growth inhibition induced by 1,25-dihydroxyvitamin D3 have been noted in certain human malignant melanoma cell lines. In this study, widely disparate levels of VDR mRNA expression were demonstrated in a panel of eight human malignant melanoma cell lines. Quantitation of receptor level by ligand binding assay showed a similar pattern. Proliferation and growth curve analysis was performed in two cell lines: RPMI 7951 (high VDR) and SK-MEL-28 (low VDR). Significant growth inhibition was noted in RPMI 7951 cells at 10(-9) M 1,25-dihydroxyvitamin D3. SK-MEL-28 cells, which express much lower levels of VDR, did not show any growth inhibition except at extremely high concentrations of 1,25-dihydroxyvitamin D3, namely 10(-5) M. These findings suggest a receptor-mediated mechanism of growth inhibition for 1,25-dihydroxyvitamin D3 and a role for this hormone in the growth of malignant melanoma cells.

Pre-employment screening: use or ornament?

Pre-employment screening (PES) in an occupational health department (OHD) in Inner London was evaluated by establishing its resource implications and devising methods to estimate its efficiency and effectiveness. The attitudes of those involved in PES were also examined. While coverage of student nurses applicants was in the region of 100 per cent, only 43 per cent of all other new employees were screened. Student nurse applicants were more likely to be referred to an occupational health nurse or doctor than other employees (45 per cent nurses, 18 per cent others), but only one person had been rejected on health grounds, as a result, during the previous 15 months. The majority of reasons for sickness absence or early retirement could not have been predicted by PES. Opinions as to the purpose of PES varied from employees who in general thought that PES was designed to protect their interests, to managers, who thought it was to protect theirs.