Search

The alpha4beta1 integrin (very late antigen-4, VLA-4) plays an important role in the migration of lymphocytes, monocytes, and eosinophils, but not neutrophils, to sites of inflammation. Pharmacological antagonism of VLA-4 is an attractive prospect for the treatment of predominantly eosinophil mediated diseases such as asthma and allergic rhinitis. We report here on a potent and selective, small molecule VLA-4 inhibitor, (2S)-3-(2', 5'-dichlorobiphenyl-4-yl)-2-({[1-(2-methoxybenzoyl)piperidin-3-yl]carbonyl}amino) propanoic acid, compound 1, and characterize the antagonist activities of this molecule in various cell-based assays and in an animal model of eosinophil migration. Compound 1 inhibited VLA-4/ vascular cell adhesion molecule-1(VCAM-1) interactions with in vitro potencies (IC50 value of 210 nM) in VLA-4-expressing Ramos cells, although the compound did not inhibit cell adhesion to fibronectin via alpha5beta1 integrin (very late antigen-5, VLA-5). Blockade of phorbol-12-myristate-13-acetate (PMA)- or Mn2+-stimulated VLA-4 interactions with compound 1 was observed in human T lymphocytes (IC50 value of 230 nM), human eosinophils (IC50 value of 4.0 microM) and mouse eosinophils (IC50 value of 1.6 microM). Furthermore, compound 1 administered by intraperitoneal injection inhibited eosinophil infiltration in a dose-dependent manner by up to 80% in an air pouch model. These data support the use of small molecule VLA-4 antagonists in the treatment of relevant diseases, such as asthma, atopic dermatitis, or allergic rhinitis.

Chlorinated aromatic contaminants are active in carcinogenic processes within the skin and may have the potential to modulate ultraviolet radiation (UV)-induced skin carcinogenesis. Exposure to a complex environmental PCB/PCDD/PCDF mixture (polychlorinated biphenyls/polychlorinated dibenzo-p-dioxins/polychlorinated dibenzofurans) during the irradiation phase of photocarcinogenesis was associated with significant (P < or = 0.001) reductions in papilloma incidence and squamous cell carcinoma multiplicity at irradiated skin sites. This protective effect was associated with significantly (P < 0.0001) reduced chronic epidermal thickening in UV and contaminant-exposed mice compared with mice exposed to UV only. Contaminant exposure was also associated with increased UV absorbance of skin methanol extracts implying a sunscreen-like effect., (Copyright 2002 Elsevier Science Ireland Ltd.)

3,3',4,4'-Tetrachlorobiphenyl (tetraCB) binds to the aryl hydrocarbon receptor (AhR), and several reports have demonstrated that AhR agonists exhibit antiestrogenic and antitumorigenic activities in human breast cancer cells, the rodent uterus and breast. In contrast, a recent study showed that 3,3',4,4'-tetraCB bound the estrogen receptor (ER) and exhibited ER agonist activities, and we therefore have reinvestigated the estrogenic and antiestrogenic activities of 3,3',4,4'-tetraCB. Our results showed that 3,3',4,4'tetraCB and a structurally related analog, 3,3',4,4',5-pentaCB, did not bind the mouse uterine or human ER, did not induce proliferation of MCF-7 or T47D human breast cancer cells or induce reporter gene activity in cells transfected with E2-responsive constructs derived from the creatine kinase B (pCKB) or cathepsin D (pCD) gene promoters. Moreover, 3,3',4,4'-tetraCB and 3,3',4,4',5-pentaCB did not induce an increase in uterine wet weight, peroxidase activity or progesterone receptor binding in the 21-25-day-old female B6C3F1 mouse uterus. In contrast, both compounds inhibited 17beta-estradiol (E2)-induced cell proliferation and transactivation in MCF-7/T47D cells and uterine responses in B6C3F1 mice; surprisingly inhibition of E2-induced reporter gene activity was not observed in T47D cells transfected with pCKB, and this was observed as a cell-specific response with other AhR agonists. Additionally, 3,3',4,4'-tetraCB significantly inhibited mammary tumor growth in female Sprague-Dawley rats initiated with 7,12-dimethylbenzanthracene. Our results indicate that 3,3',4,4'-tetraCB does not exhibit ER agonist activity but exhibits a broad spectrum of antiestrogenic responses consistent with ligand-mediated AhR-ER crosstalk.

3,3',4,4',5-Pentachlorobiphenyl (pentaCB) caused a dose-dependent induction of fetal cleft palate in offspring from pregnant C57BL/6 mice exposed to a single dose (783 or 1044 micrograms/kg) of this compound on gestation day 10. In contrast, 2,2',4,4',5,5'-hexaCB did not cause cleft palate at a dose of 271 mg/kg and, in pregnant mice cotreated with 2,2',4,4',5,5'-hexaCB (271 mg/kg) plus 783 or 1044 micrograms/kg 3,3',4,4',5-pentaCB, fetal cleft palate formation was significantly inhibited. 3,3',4,4',5-PentaCB (6 micrograms/kg) also inhibited the splenic plaque-forming cell (PFC) response and serum IgM levels in C57BL/6 mice treated with the T cell-independent antigen trinitrophenyl-lipopolysaccharide. At doses as high as 72 mg/kg, 2,2',4,4'-5,5'-hexaCB was not immunotoxic; however, in mice cotreated with a immunotoxic dose of 3,3',4,4',5-pentaCB plus different doses of 2,2',4,4',5,5'-hexaCB (18, 36 and 72 mg/kg), there was a dose-dependent inhibition of 3,3',4,4',5-pentaCB-induced immunotoxicity. These non-additive (antagonistic) interactions of prototypical polychlorinated biphenyl (PCB) congeners may be an important consideration in development of a toxic equivalency factor approach for hazard and risk assessment of PCB mixtures.