Acute exposure of human lung cells to 1,3-butadiene diepoxide results in G1 and G2 cell cycle arrest.

1,3-Butadiene (BD) causes genetic damage, including adduct formation, sister chomatid exchange, and point mutations. Previous studies have focused on the types of genetic damage and tumors found after long-term exposure of rodents to butadiene. This study examined the effect of the most active BD metabolite, butadiene diepoxide (BDO2), on cell cycle entry and progression in human lung fibroblasts (LU cells) with a normal diploid karyotype. Serum-arrested (G0) LU cells were exposed to BDO2 for 1 hr and stimulated to divide with medium containing 10% fetal bovine serum. The BDO2-treated LU cells were evaluated for cell cycle progression, nuclear localization of arrest mediators, mitotic index, and cellular proliferation. The BDO2-treated cells demonstrated a substantial inhibition of cell proliferation when treated with 100 microM BDO2 for 1 hr. No appreciable levels of apoptosis or mitotic figures were observed in the BDO2-treated cells through 96 hr posttreatment. Flow cytometric analysis revealed that the lack of proliferation in BDO2-treated LU cells was related to G1 arrest in about half of the cells and a delayed progression through S and G2 arrest in nearly all of the remaining cells. Both G1 and G2 arrest were prolonged and only a very small percentage of BDO2-treated cells were eventually able to replicate. Increased nuclear localization of both p53 and p21(cip1) was observed in BDO2-treated cells, suggesting that the cell cycle arrest was p21(cip1)-mediated. These results demonstrate that BDO2 induces cell cycle perturbation and arrest even with short-term exposure that does not produce other pathologic cellular effects.

Induction of a potential paracrine angiogenic loop between human THP-1 macrophages and human microvascular endothelial cells during Bartonella henselae infection.

Bartonella henselae is responsible for various disease syndromes that loosely correlate with the immune status of the host. In the immunocompromised individual, B. henselae-induced angiogenesis, or bacillary angiomatosis, is characterized by vascular proliferative lesions similar to those in Kaposi's sarcoma. We hypothesize that B. henselae-mediated interaction with immune cells, namely, macrophages, induces potential angiogenic growth factors and cytokines which contribute in a paracrine manner to the proliferation of endothelial cells. Vascular endothelial growth factor (VEGF), a direct inducer of angiogenesis, and interleukin-1beta (IL-1beta), a potentiator of VEGF, were detected within 12 and 6 h, respectively, in supernatants from phorbol 12-myristate 13-acetate-differentiated human THP-1 macrophages exposed to live B. henselae. Pretreatment of macrophages with cytochalasin D, a phagocytosis inhibitor, yielded comparable results, suggesting that bacterium-cell attachment is sufficient for VEGF and IL-1beta induction. IL-8, an angiogenic cytokine with chemotactic properties, was induced in human microvascular endothelial cells (HMEC-1) within 6 h of infection, whereas no IL-8 induction was observed in infected THP-1 cells. In addition, conditioned medium from infected macrophages induced the proliferation of HMEC-1, thus demonstrating angiogenic potential. These data suggest that Bartonella modulation of host or target cell cytokines and growth factors, rather than a direct role of the bacterium as an endothelial cell mitogen, is the predominant mechanism responsible for angiogenesis. B. henselae induction of VEGF, IL-1beta, and IL-8 outlines a broader potential paracrine angiogenic loop whereby macrophages play the predominant role as the effector cell and endothelial cells are the final target cell, resulting in their proliferation.

Role of Bartonella henselae in the etiology of Henoch-Schönlein purpura.

BACKGROUND: The etiology of Henoch-Schönlein purpura (HSP) has been ascribed to a variety of infectious and noninfectious agents. Because we encountered a patient with HSP who had evidence of Bartonella henselae infection and a prior report of a patient with systemic cat-scratch disease presenting as leukoclastic vasculitis, we investigated the association of B. henselae infection with HSP. METHODS: We determined the antibody titers to B. henselae on the sera of 18 patients with HSP and on 57 controls. All patients presented with the characteristic leukoclastic rash of HSP. About one-half of the patients had joint or abdominal symptoms, and four had hematuria at presentation. An indirect immunofluorescent assay was used to determine serum antibody titers to B. henselae. Sera that were reactive at a dilution of 1/64 were considered positive. RESULTS: Eight of the 57 (14%) control sera and 12 of the 18 (67%) patient sera were positive for B. henselae antibody (P < 0.0001). CONCLUSION: The results of this study indicate a significant association of antecedent B. henselae infection with HSP. The frequency of this association (67%) exceeds that of previously ascribed etiologic agents for this disease, such as the group A Streptococcus.