Studies have been carried out previously to determine whether mesenchymal stem cells (MSC) influence the progression of pulmonary fibrosis. Here, we asked whether MSC (derived from mouse bone marrow and human umbilical cord blood) produce factors that mediate lung fibroblast (LF) growth and matrix production. MSC-conditioned media (CM) were found by ELISA to contain significant amounts of PDGF-AA and transforming growth factor-beta1 (TGF-beta1). Proliferation was increased in a concentration-dependent manner in LF cell lines and primary cells cultured in MSC-CM, but neither anti-PDGF antibodies nor PDGF receptor-specific antibodies affected proliferation, nor did a number of other antibodies to well-known mitogenic factors. However, proliferation was significantly inhibited by the Wnt signaling antagonist, secreted frizzled related protein-1 (sFRP-1). In addition, anti-Wnt1 and anti-Wnt2 antibodies attenuated MSC-CM-induced proliferation, and increased expression of Wnt7b was identified. As would be expected in cells activated by Wnt, nuclear beta-catenin was increased. The amount of TGF-beta1 in MSC-CM and its biological activity were revealed by activation at acidic pH. The stem cells synthesized and released TGF-beta1 that increased alpha1-procollagen gene expression by LF target cells. Addition of anti-TGF-beta to the MSC-CM blocked upregulation of collagen gene expression. These data demonstrate that MSC from mice and humans produce Wnt proteins and TGF-beta1 that respectively stimulate LF proliferation and matrix production, two hallmarks of fibroproliferative lung disease. It will be essential to determine whether these factors can play a role in attempts to use MSC for therapeutic approaches.

Propanil (3,4-dichloropropionanilide) and 2,4-D (2,4-dichlorophenoxyacetic acid) are commonly used herbicides that have toxic effects on the immune system. The present study determined the effect of exposure to these chemicals on the immune response to a bacterial vaccine. The antibody responses to the T-independent type 2 antigen, phosphorylcholine (PC) and the T-dependent antigen, pneumococcal surface protein A (PspA) were characterized in C57BL/6 mice after heat-killed Streptococcus pneumoniae (HKSP) immunization and single or mixture herbicide exposure. Propanil exposure significantly increased the number of PC-specific IgM, IgG2b, and IgG3 antibody-secreting B cells (ASC) in the spleen 4-6-fold over control animals in a dose-dependent manner. However, the number of ASC in the bone marrow and serum titers were comparable in control and propanil-treated mice. In contrast, 2,4-D exposure decreased the number of PC-specific IgM and IgG bone marrow ASC 2-3-fold from control animals. The decrease in bone marrow ASC in 2,4-D-treated mice corresponded to a 3-4-fold decrease in PC-specific IgM, IgG2b, and IgG3 serum titers compared to control mice. The number of ASC in the spleens of 2,4-D-treated mice was, however, comparable to control mice. The antibody response to PspA was not affected by any of the treatments. There were no mixture interactions between the two herbicides in any of the responses measured. These results characterize the primary PC-specific antibody response in the bone marrow, spleen, and serum after HKSP vaccination and herbicide exposure. The differential effects of propanil and 2,4-D on the antibody response to a bacterial vaccine demonstrate the potential of chemical exposure to augment or suppress immune responses to vaccines and infectious diseases.

Steroid hormones are known to affect the humoral immune response to a variety of antigens. However, the mechanisms regulating these effects are poorly understood. The immunotoxic chemical propanil and estrogen have similar effects on the immune system including augmentation of humoral immune responses. Propanil enhances the number of phosphorylcholine (PC)-specific IgG2b, IgG3, and IgM antibody-secreting cells (ASCs) in the spleen four- to sixfold 7 days after vaccination of female C57BL/6 mice with heat-killed Streptococcus pneumoniae. Several experiments were performed to test the hypothesis that propanil increases the response via an estrogenic pathway. Ovariectomy abrogated the effect of propanil on the PC-specific ASC response. Both in vitro and in vivo assays indicate that propanil does not bind either estrogen receptor (ER) alpha or beta. Exogenous estradiol administration in ovariectomized mice failed to restore the effect of propanil on the PC response. Treatment of female mice with a pure ER antagonist, ICI 182,780, or the progesterone antagonist RU486 did not inhibit the increase in ASCs. These data suggest that estrogen and progesterone do not regulate the effect of propanil. However, complete inhibition of steroid synthesis with the gonadotropin-releasing hormone (GnRH) antagonist antide abrogated the increased response in propanil-treated mice, indicating a necessary role for steroid synthesis. Experiments in male mice demonstrated that propanil increased the number of ASCs comparable to female mice. However, orchiectomy did not inhibit this effect, suggesting that androgens do not regulate the amplification of the humoral response. These data suggest a novel role for the ovarian hormones in the regulation of the PC-specific antibody response.

The pesticide 3,4-dichloropropionanilide (propanil or, alternatively, DCPA) is a member of the acetanilide chemical family and is predominantly used for the control of weeds on commercial rice crops worldwide. This article was written to provide a brief review of the general toxicity of propanil followed by a detailed summary of the immunotoxicity studies that were performed to date in mammalian in vivo and in vitro models. Propanil affects the immune system at organ, cellular, and molecular levels. Studies demonstrated that it produces thymic atrophy and splenomegaly and decreases developing T- and B-cell populations in the thymus and bone marrow. Natural killer (NK) cells and macrophages are critical components of the innate immune system. NK cell cytotoxicity and the ability of macrophages to phagocytose, kill pathogenic bacteria, and produce inflammatory cytokines are suppressed by propanil. Propanil also affects the respiratory burst of macrophages, inhibiting reactive oxygen and nitrogen species production. Molecular mechanisms responsible for propanil's effects have begun to be elucidated and include alterations in nuclear factor (NF)-kappaB transcription factor activity and intracellular Ca(2+) signaling. Propanil exposure alters a number of functions of mature T lymphocytes and B lymphocytes that impacts the adaptive immune response. T-cell cytotoxic activity and cytokine production are major T-cell functions inhibited by propanil. The humoral antibody response to model antigens and intact bacteria is differentially affected after propanil exposure. How these changes in innate and adaptive immune responses impact the host response to bacterial challenge or vaccination has begun to be examined.

Mesenchymal stem cells (MSCs) have been shown to differentiate into a variety of mesenchymal cell types, including fibroblasts, myofibroblasts, osteoblasts, chondroblasts, adipocytes, and myoblasts, as well as epithelial cells. It has been shown that these cells can be recovered from bone marrow as well as umbilical cord blood, and they can be propagated, stored, and administered to animals and patients in clinical trials. It is clear that the cells engraft in the lung, and several laboratories have demonstrated an ameliorating effect in models of acute injury caused by LPS and in chronic lung injury induced by bleomycin and asbestos. However, it is not at all clear under what conditions these cells must be applied to provide an advantage and when using these cells might cause exacerbation of the lung injury. This brief review focuses on the biology of MSCs in vitro, how the cells have been used in some animal models, and the potential for their use in therapeutic strategies for diseases as diverse as lung cancer and interstitial fibrosis.