The fibrillar collagen types I, II, and V/XI have recently been shown to have partially 3-hydroxylated proline (3Hyp) residues at sites other than the established primary Pro-986 site in the collagen triple helical domain. These sites showed tissue specificity in degree of hydroxylation and a pattern of D-periodic spacing. This suggested a contributory role in fibril supramolecular assembly. The sites in clade A fibrillar ␣1(II), ␣2(V), and ␣1(I) collagen chains share common features with known prolyl 3-hydroxylase 2 (P3H2) substrate sites in ␣1(IV) chains implying a role for this enzyme. We pursued this possibility using the Swarm rat chondrosarcoma cell line (RCS-LTC) found to express high levels of P3H2 mRNA. Mass spectrometry determined that all the additional candidate 3Hyp substrate sites in the pN type II collagen made by these cells were highly hydroxylated. In RNA interference experiments, P3H2 protein synthesis was suppressed coordinately with prolyl 3-hydroxylation at Pro-944, Pro-707, and the C-terminal GPP repeat of the pN␣1(II) chain, but Pro-986 remained fully hydroxylated. Furthermore, when P3H2 expression was turned off, as seen naturally in cultured SAOS-2 osteosarcoma cells, full 3Hyp occupancy at Pro-986 in ␣1(I) chains was unaffected, whereas 3-hydroxylation of residue Pro-944 in the ␣2(V) chain was largely lost, and 3-hydroxylation of Pro-707 in ␣2(V) and ␣2(I) chains were sharply reduced. The results imply that P3H2 has preferred substrate sequences among the classes of 3Hyp sites in clade A collagen chains.Collagen, the major structural protein of vertebrates has evolved a range of post-translational modifications that are essential for triple helix assembly and stability, intermolecular cross-linking, and strength of fibrils and tissue function. Enzymes from the family of 2-oxo-glutarate-dependent dioxygenases are responsible for most of these modifications. For example, prolyl 4-hydroxylase catalyzes proline 4-hydroxylation, a modification necessary for the secondary and tertiary structure of collagen (1, 2), and the lysyl hydroxylase isoenzymes catalyze lysine hydroxylation, a modification essential for the formation of intermolecular cross-links in collagen (2-4).Prolyl 3-hydroxlase 1 (P3H1), 2 another member of the 2-oxo-glutarate-dependent dioxygenase family, catalyzes the post-translational 3-hydroxylation of certain proline residues in fibril-forming collagens. This enzyme was only recently cloned from chicken tissues (5) after being partially purified Ͼ25 years ago (6). P3H1 was identified as the chick homologue of rat leprecan, a glycoprotein, which was first isolated from a rat parietal yolk sac tumor cell line (7). Within the past few years, novel mutations in the human P3H1 gene and genes encoding P3H1-associated proteins were shown to cause recessive forms of osteogenesis imperfecta (8 -11). By mass spectrometry, we and other investigators have shown that Pro-986 in the ␣1(I) collagen chain of bone and skin from such patients can be severely under-3-hydroxyated. The P3H1 enz...

Severe infection with respiratory syncytial virus (RSV) in children can progress to respiratory distress and acute lung injury (ALI). Accumulating evidence suggests that mechanical ventilation (MV) is an important cofactor in the development of ALI by modulating the host immune responses to bacteria. This study investigates whether MV enhances the host response to pneumonia virus of mice (PVM), a mouse pneumovirus that has been used as a model for RSV infection in humans. BALB/c mice were inoculated intranasally with diluted clarified lung homogenates from mice infected with PVM strain J3666 or uninfected controls. Four days after inoculation, the mice were subjected to 4 h of MV (tidal volume, 10 ml/kg) or allowed to breathe spontaneously. When compared with that of mice inoculated with PVM only, the administration of MV to PVM-infected mice resulted in increased bronchoalveolar lavage fluid concentrations of the cytokines macrophage inflammatory protein (MIP)-2, MIP-1alpha (CCL3), and IL-6; increased alveolar-capillary permeability to high molecular weight proteins; and increased caspase-3 activity in lung homogenates. We conclude that MV enhances the activation of inflammatory and caspase cell death pathways in response to pneumovirus infection. We speculate that MV potentially contributes to the development of lung injury in patients with RSV infection.

Cysteine-rich protein-61 (CYR61), also known as connective tissue growth factor, CYR61, and nephroblastoma overexpressed gene 1 (CCN1), is a heparin-binding protein member of the CCN family of matricellular proteins. Gene expression profiles showed that Cyr61 is upregulated in human acute lung injury (ALI), but its functional role is unclear. We hypothesized that CYR61 contributes to ALI in mice. First, we demonstrated that CYR61 expression increases after bleomycin-induced lung injury. We then used adenovirus-mediated gene transfer to determine whether CYR61 overexpression in the lungs was sufficient to cause ALI. Mice instilled with CYR61 adenovirus showed greater weight loss, increased bronchoalveolar lavage total neutrophil counts, increased protein concentrations, and increased mortality compared with mice instilled with empty-vector adenovirus. Immunohistochemical studies in lungs from humans with idiopathic pulmonary fibrosis revealed CYR61 expression on the luminal membrane of alveolar epithelial cells in areas of injury. We conclude that CYR61 is upregulated in ALI and that CYR61 overexpression exacerbates ALI in mice.

Activation of the Fas/Fas ligand (FasL) system in the lungs results in a form of injury characterized by alveolar epithelial apoptosis and neutrophilic inflammation. Studies in vitro show that Fas activation induces apoptosis in alveolar epithelial cells and cytokine production in alveolar macrophages. The main goal of this study was to determine the contribution of alveolar macrophages to Fas-induced lung inflammation in mice, by depleting alveolar macrophages using clodronate-containing liposomes. Liposomes containing clodronate or PBS were instilled by intratracheal instillation. After 24 h, the mice received intratracheal instillations of the Fas-activating monoclonal antibody Jo2 or an isotype control antibody and were studied 18 h later. The Jo2 MAb induced increases in bronchoalveolar lavage fluid (BALF) total neutrophils, lung caspase-3 activity, and BALF total protein and worsened histological lung injury in the macrophage-depleted mice. Studies in vitro showed that Fas activation induced the release of the cytokine KC in a mouse lung epithelial cell line, MLE-12. These results suggest that the lung inflammatory response to Fas activation is not primarily dependent on resident alveolar macrophages and may instead depend on cytokine release by alveolar epithelial cells.