REGULATION OF ALVEOLAR MACROPHAGE FUNCTION IN ASBESTOSIS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. One important characteristic of alveolar macrophages obtained from the lungs of asbestosis patients is they resemble monocyte-like cells. In addition, alveolar macrophages obtained from patients with asbestosis spontaneously release cytokines. The focus of this protocol is to determine the mechanisms necessary to elicit cytokine production by macrophages exposed to asbestos and to explore the functional differences between normal alveolar macrophages and monocytes or monocyte-like cells obtained from patients with asbestosis. Preliminary data indicate that normal alveolar macrophages, unlike blood monocytes, do not produce cytokines when stimulated, in vitro, with asbestos. These data also show that normal alveolar macrophages produce more reactive oxygen species (ROS) after exposure to asbestos than do blood monocytes. Studies have demonstrated that the p38 mitogen-activated protein (MAP) kinase is linked to cytokine gene expression in macrophages through its modulation of TATA-binding protein (TBP) activation, and ROS differentially activate MAP kinases. These investigators hypothesize that asbestos does not cause cytokine gene expression in normal alveolar macrophages due to lack of p38 MAP kinase activation. Thus, the functional difference between normal alveolar macrophages and monocyte-like cells is, in part, due to differences in p38 MAP kinase activity. In Aim 1, they will determine if asbestos-induced ROS, especially hydroxyl radical, produced in normal alveolar macrophages inactivate the p38 MAP kinase by inhibiting the upstream kinases that activate p38 and/or by activating phosphatases. Specifically, the new contributions for asbestos will be to compare the generation of ROS in alveolar macrophages and blood monocytes; to determine if asbestos-induced ROS down-regulates the p38 MAP kinase in alveolar macrophages; and to determine if asbestos induces the activity of phosphatases that inactivate the p38 MAP kinase. In Aim 2 they will determine if asbestos increases NF-kB- and AP-1-driven transcription in normal macrophages compared to monocytes by evaluating the interaction of TBP with NF-kB and AP-1 proteins. They will also compare TBP phosphorylation and binding to the TATA box in alveolar macrophages and blood monocytes. In Aim 3 they will determine if reactivation of p38 MAP kinase results in the ability of normal macrophages, under these conditions, to express cytokine genes. They also plan to evaluate p38 MAP kinase activity and ROS generation in macrophages obtained from patients with asbestosis. Although the studies in this protocol relate to asbestosis, they are novel studies that also provide important basic clues to understand macrophage cytokine gene regulation and the functional difference between alveolar macrophages and monocyte-like cells.