Selective induction of PDGF gene expression in peritoneal macrophages by interleukin-2

Aberrant mural cell recruitment to lymphatic vessels and impaired lymphatic drainage in a murine model of pulmonary fibrosis

Pulmonary fibrosis is a progressive disease with unknown etiology that is characterized by extensive remodeling of the lung parenchyma, ultimately resulting in respiratory failure. Lymphatic vessels have been implicated with the development of pulmonary fibrosis, but the role of the lymphatic vasculature in the pathogenesis of pulmonary fibrosis remains enigmatic. Here we show in a murine model of pulmonary fibrosis that lymphatic vessels exhibit ectopic mural coverage and that this occurs early during the disease. The abnormal lymphatic vascular patterning in fibrotic lungs was driven by expression of platelet-derived growth factor B (PDGF-B) in lymphatic endothelial cells and signaling through platelet-derived growth factor receptor (PDGFR)-β in associated mural cells. Because of impaired lymphatic drainage, aberrant mural cell coverage fostered the accumulation of fibrogenic molecules and the attraction of fibroblasts to the perilymphatic space. Pharmacologic inhibition of the PDGF-B/PDGFR-β signaling axis disrupted the association of mural cells and lymphatic vessels, improved lymphatic drainage of the lung, and prevented the attraction of fibroblasts to the perilymphatic space. Our results implicate aberrant mural cell recruitment to lymphatic vessels in the pathogenesis of pulmonary fibrosis and that the drainage capacity of pulmonary lymphatics is a critical mediator of fibroproliferative changes.

Expression of DNA topoisomerases in chronic proliferative kidney disease

BACKGROUND

Circulating autoantibodies to human topoisomerases have been reported in glomerular kidney disease associated with scleroderma and systemic lupus erythematosus. However, limited information is available about the expression of topoisomerases in the kidney under normal and pathological conditions.

METHODS

The expression of DNA topoisomerases I and IIalpha was studied by immunohistochemistry on archival biopsies from 70 patients with chronic renal diseases. Normal kidney tissue was examined for comparison. Topoisomerase I was detected by means of monoclonal antibody (mAb) C21, and topoisomerase IIalpha was detected by means of mAb Ki-S4. In addition, mAb Ki-M1p was used to assess the density of monocytic infiltrates. All parameters were assessed in a semiquantitative manner.

RESULTS

Glomerular topoisomerase IIalpha levels were increased in mesangial proliferative glomerulonephritis (MPGN), rapidly progressive glomerulonephritis (RPGN), and lupus nephritis (LN) and were reduced in membranous glomerulonephritis (MGN), chronic transplant nephropathy (CTN), and tubulointerstitial nephritis (TIN). Tubular epithelia displayed high topoisomerase IIalpha levels in mesangiocapillary glomerulonephritis (MCGN), RPGN, TIN, miscellaneous entities (MISC) and LN, and displayed low levels in MPGN and CTN. Topoisomerase I expression was high in the glomeruli of focal segmental glomerulosclerosis (FSGS), MCGN, and RPGN and was extreme in LN, whereas it was strikingly diminished in the glomeruli of MGN, CTN, and TIN. Almost all conditions displayed lower tubular topoisomerase I levels than normal kidney, except for LN, in which the enzyme content was markedly increased. Increased glomerular monocytic infiltrates were found in FSGS, MCGN, RPGN, TIN, and LN, and tubulointerstitial Ki-M1p+ cells were seen at high numbers in MCGN, RPGN, TIN, MISC, and LN. The expression of the topoisomerases I and IIalpha was significantly correlated; also, topoisomerases showed a positive association with the density of monocytic infiltrates. The parameter profiles exhibited significant differences between distinct types of chronic renal disease.

CONCLUSION

Topoisomerase IIalpha expression is tightly linked to cell cycling, and topoisomerase I is likely a reflection of gene transcription. Rapidly progressing glomerular disease therefore appears to be accompanied by active mesangial cell proliferation and increased metabolic activity in glomerular cells. The correlation with inflammatory infiltrates is likely to reflect a positive feedback mechanism involving cytokines, growth factors, and adhesion molecules. Assessment of topoisomerases may therefore be of diagnostic help and might allow prognostic predictions. Provided that our observations are supported by clinicopathological follow-up studies, one might envisage the use of topoisomerase inhibitors in the therapy of chronic proliferative renal disease refractory to current treatment protocols.

The inflammatory response system of brain: implications for therapy of Alzheimer and other neurodegenerative diseases

Cultured brain cells are capable of generating many molecules associated with inflammatory and immune functions. They constitute the endogenous immune response system of brain. They include complement proteins and their regulators, inflammatory cytokines, acute phase reactants and many proteases and protease inhibitors. Most of the proteins are made by microglia and astrocytes, but even neurons are producers. Many appear in association with Alzheimer disease lesions, indicating a state of chronic inflammation in Alzheimer disease brain. Such a state can apparently exist without stimulation by peripheral inflammatory mediators or the peripheral immune system. A strong inflammatory response may be autotoxic to neurons, exacerbating the fundamental pathology in Alzheimer disease and perhaps other neurological disorders. Autotoxic processes may contribute to cellular death in chronic inflammatory diseases affecting other parts of the body, suggesting the general therapeutic value of anti-inflammatory agents. With respect to Alzheimer disease, multiple epidemiological studies indicate that patients taking anti-inflammatory drugs or suffering from conditions in which such drugs are routinely used, have a decreased risk of developing Alzheimer disease. In one very preliminary clinical trial, the anti-inflammatory drug indomethacin arrested progress of the disease. New agents directed against the inflammatory processes revealed in studies of Alzheimer disease lesions may have broad therapeutic applications.