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Bacterial infections after lung transplantation cause airway epithelial injury and are associated with an increased risk of developing bronchiolitis obliterans syndrome. The damaged epithelium is a source of alarmins that activate the innate immune system, yet their ability to activate fibroblasts in the development of bronchiolitis obliterans syndrome has not been evaluated. Two epithelial alarmins were measured longitudinally in bronchoalveolar lavages from lung transplant recipients who developed bronchiolitis obliterans syndrome and were compared to stable controls. In addition, conditioned media from human airway epithelial cells infected with Pseudomonas aeruginosawas applied to lung fibroblasts and inflammatory responses were determined. Interleukin‐1 alpha (IL‐1α) was increased in bronchoalveolar lavage of lung transplant recipients growing P. aeruginosa(11.5 [5.4–21.8] vs. 2.8 [0.9–9.4] pg/mL, p < 0.01) and was significantly elevated within 3 months of developing bronchiolitis obliterans syndrome (8.3 [1.4–25.1] vs. 3.6 [0.6–17.1] pg/mL, p < 0.01), whereas high mobility group protein B1 remained unchanged. IL‐1α positively correlated with elevated bronchoalveolar lavage IL‐8 levels (r2= 0.6095, p < 0.0001) and neutrophil percentage (r2= 0.25, p = 0.01). Conditioned media from P. aeruginosainfected epithelial cells induced a potent pro‐inflammatory phenotype in fibroblasts via an IL‐1α/IL‐1R‐dependent signaling pathway. In conclusion, we propose that IL‐1α may be a novel therapeutic target to limit Pseudomonasassociated allograft injury after lung transplantation. This study demonstrates that a Pseudomonas aeruginosachallenge of lung epithelial cells causes the release of IL‐1α and the induction of an inflammatory phenotype in lung fibroblasts, and provides evidence of an association between infection with P. aeruginosa,IL‐1α levels in bronchoalveolar lavage fluid, and the development of bronchiolitis obliterans syndrome following lung transplantation.

Periaxin was first described as a 147-kDa protein that was suggested to have a potential role in the initiation of myelin deposition in peripheral nerves based upon its abundance, cell type specificity, pattern of developmental expression, and localization (Gillespie, C. S., Sherman, D. L., Blair, G. E., and Brophy. P. J. (1994) Neuron 12, 497-508). Here we show that the murine periaxin gene spans 20.6 kilobases and encodes two mRNAs of 4.6 and 5.2 kilobases that encode two periaxin isoforms, L-periaxin and S-periaxin of 147 and 16 kDa respectively. The larger mRNA is produced by a retained intron mechanism that introduces a stop codon and results in a truncated protein with an intron-encoded C terminus of 21 amino acids. Both proteins possess a PDZ domain at the N terminus; nevertheless, they are targeted differently in Schwann cells. Like other proteins that contain PDZ domains, L-periaxin is localized to the plasma membrane of myelinating Schwann cells: in contrast, S-periaxin is expressed diffusely in the cytoplasm. This suggests that proteins that contain this protein-binding module may also participate in protein-protein interactions at sites other than the cell cortex.

Extraction of rat brain myelin in a buffer containing Triton X-100 yielded a soluble fraction and an insoluble residue that was enriched in cytoskeletal elements. Immunoblot analysis of the detergent-soluble fraction and the insoluble cytoskeletal residue showed that all of the tubulin and more than half of the actin were found within the cytoskeletal fraction. The distribution of myelin-specific proteins was also examined, and revealed that 2′,3′-cyclic nucleotide 3′-phosphohydrolase (CNPase) I and most of the myelin basic proteins (MBPs) were equally distributed between both fractions. By contrast, the large MBP (21.5 kDa) and CNPase II (50 kDa) were observed to partition almost entirely with the cytoskeletal fraction. Proteolipid protein was found predominantly in the detergent-soluble fraction, as was DM-20 protein. Analysis of the cytoskeletal fraction by sucrose-density-gradient centrifugation demonstrated that a distinct subset of lipids was tightly bound to the cytoskeletal protein residue. The cytoskeleton-associated lipid was considerably enriched in cerebroside and sphingomyelin by comparison with total myelin lipids. These results indicate that a cytoskeletal matrix is associated with multilamellar myelin, and suggest that this structure may play a fundamental role in myelinogenesis.

Immature Schwann cells of the rat sciatic nerve can differentiate into myelin-forming or non-myelin-forming cells. The factors that influence this divergent development are unknown but certain markers such as galactocerebroside distinguish the two cell populations at an early stage of Schwann cell differentiation. Because myelination requires extensive changes in cell morphology, we have investigated the composition and structure of the Schwann cell cytoskeleton at a time when these cells become committed to myelination. Here we show that Schwann cells express a cytoskeletal protein of M(r) 145 before diverging into the myelin-forming path, i.e., before they acquire cell-surface galactocerobroside. The p145 protein has the characteristics of an intermediate filament (IF) protein and immunoelectron microscopy shows that it colocalizes with vimentin, which suggests that these two proteins can coassemble into IFs. Elevated intracellular cAMP levels, which can mimic some of the early effects of axons on Schwann cell differentiation, induced p145 synthesis, therefore, we conclude that myelin-forming Schwann cells express this protein at a very early stage in their development. Immunological comparisons with other IF proteins revealed a close similarity between p145 and the neurofilament protein NF-M; the identification of p145 as NF-M was confirmed by isolating and sequencing a full-length clone from a Schwann cell cDNA library. These data demonstrate that Schwann cells remodel their IFs by expressing NF-M before acquiring the myelin-forming phenotype and that IF proteins of the neurofilament-type are not restricted to neurons in the vertebrate nervous system.

The membranes of intact C6 cells were enriched with phosphatidyldimethylethanolamine or phosphatidylmonomethylethanolamine. These cells showed enhanced rates of phospholipid methylation but this was not accompanied by an increased β-adrenergic response. We conclude that phospholipid methylation is not coupled to the activation of adenylate cyclase in the β-adrenergic response of C6 glial cells.