Eotaxin represents the principal eosinophil chemoattractant in a novel murine asthma model induced by house dust containing cockroach allergens.

Asthma represents a serious health problem particularly for inner city children, and recent studies have identified that cockroach allergens trigger many of these asthmatic attacks. This study tested the concept that asthma-like pulmonary inflammation may be induced by house dust containing cockroach allergens. An aqueous extract was prepared from a house dust sample containing endotoxin and high levels of cockroach allergens. BALB/c mice were immunized with the house dust extract (HDE) and received two additional pulmonary challenges. Bronchoalveolar lavage (BAL) eosinophil counts and eotaxin levels were significantly increased in immunized mice exposed to the HDE, whereas neutrophils were the predominant BAL inflammatory cell in the unimmunized mice. Kinetics studies in immunized mice demonstrated a peak pulmonary inflammatory response 48 h after the last challenge. The allergic response in this model was further confirmed by histological and physiological studies demonstrating a significant influx of eosinophils and lymphocytes in the peribronchial area, and severe airway hyperreactivity through whole-body plethysmography. The specificity of the response was established by immunizing with HDE and challenging with purified cockroach allergen, which induced pulmonary eosinophilia and airway hyperreactivity. Ab inhibition of eotaxin significantly inhibited the number of BAL eosinophils. These data describe a novel murine model of asthma-like pulmonary inflammation induced by house dust containing endotoxin and cockroach allergens and further demonstrate that eotaxin represents the principal chemoattractant for the recruitment of the pulmonary eosinophils.

Imbalances in N-CAM, SAM and polysialic acid may underlie the paranodal ion channel barrier defect in diabetic neuropathy.

Breakdown of protective tissue barrier systems characterizes the chronic diabetic complications affecting the retina, and peripheral and central nerve tracts. The progressive damages to the blood-retina-, blood-nerve-, and paranodal ion channel barriers have pathophysiological consequences for the relentless progression of these complications. The continuing damage to the paranodal ion channel barrier in the spontaneously diabetic BB/W rat is associated with an increasingly irreversible nerve conduction defect, due to impaired nodal Na+ currents associated with displacement of nodal Na+ channels across the damaged paranodal barrier. The structural substrate for the mechanical barrier of the paranode is provided by electron-dense junctional complexes made up by a moiety of neural cell adhesive-(N-CAM), neural-glial adhesive (Ng-CAM), substrate adhesive molecules (SAMs) and polysialic acid (PSA). To further explore the mechanism underlying the protective barrier defect in diabetic neuropathy we examined the expression and immunolocalization of these molecules in peripheral nerve. In 6-month diabetic BB/W rats, direct and indirect ELISAs revealed significantly up-regulated N-CAM (P < 0.05), tenascin (Ng-CAM), (P < 0.001) and N-cadherin (A-CAM) (P < 0.03). On the other hand, SAMs showed little change, except for PSA which showed a significantly (P < 0.03) decreased concentration in the diabetic nerve. Immunocytochemical identification of these molecules revealed no visually detectable differences between diabetic and control rats. In conclusion, these data suggest that imbalances between highly interactive molecules responsible for the adhesiveness between terminal Schwann cell loops and the paranodal axolemma may underlie the critical paranodal barrier defect in diabetic neuropathy.

An orderly development of paranodal axoglial junctions and bracelets of Nageotte in the rat sural nerve.

The present study was designed to assess the normal development of the paranodal apparatus with particular emphasis on axoglial junctions (AGJs) which constitute the paranodal barrier system. The sural nerve was examined in 10- and 31-day-old rats. During the early phase of myelination AGJ attachment of terminal myelin loops to the axolemma proceeded from the node to the internode. The frequency of terminal loops with AGJ attachment increased with fiber growth. As myelination advanced internodal-most loops became almost 100% attached to the axolemma by AGJs, whereas at the same time an increasing number of nodal-most loops were unattached, suggesting a lack of AGJ formation at this site. The formation of bracelets of Nageotte increased with the progressive addition of myelin loops. They formed most frequently at the juxtanodal interface between unattached and attached loops, probably reflecting crowding of terminal loops along the unchanged length of the paranodal axolemma. The findings suggest a complex but orderly age- and fiber size-dependent maturation process of the paranode and its structural barrier system. The present data will serve as a basis for the evaluation of this anatomical region in regenerating and remyelinating fibers in various neuropathies.

Nerve fiber regeneration following axotomy in the diabetic biobreeding Worcester rat: the effect of ARI treatment.

Diabetic neuropathy is characterized by progressive nerve fiber degeneration resulting in nerve fiber loss. In order to examine what role impaired nerve fiber regeneration may play in the progressive net nerve fiber loss, spontaneously diabetic biobreeding Worcester (BB/W) rats were subjected to sciatic nerve axotomy at 6 weeks of diabetes. Myelinated nerve fiber regeneration was examined morphologically and morphometrically at various time points following axotomy. The data were compared with those of axotomized control rats and diabetic rats treated with an aldose reductase inhibitor (ARI) from 1 week after onset of diabetes. Diabetic rats showed a significant attenuation of nerve fiber regeneration during the first 6 weeks following axotomy, which was normalized at 4 months postaxotomy. ARI treatment resulted in an initial burst of supranormal regeneration, which was normalized at 4 months postaxotomy. Impaired nerve fiber regeneration in diabetic rats was associated with a marked delay in preceding Wallerian degeneration and decreased phagocytic activity by macrophages, changes not demonstrated in ARI-treated diabetic rats. We propose that the impaired nerve fiber regeneration in the diabetic BB/W rat may, in part, be the result of impaired recruitment and/or function of macrophages necessary for the initiation of normal nerve fiber regeneration. The corrective effects of ARI treatment on the regenerative ability of diabetic peripheral nerve suggest that an activated polyol pathway may impact on both intrinsic and extrinsic mechanisms governing nerve fiber regeneration.

Inflammatory myopathy in F1 hybrid mice with acute graft-versus-host reactions.

Polymyositis and myasthenia gravis-like syndromes have been seen in patients with GVH disease following bone marrow transplantation. We therefore investigated the histopathology of muscle in mice with acute graft-versus-host disease in order to determine whether these conditions are caused by injury from the GVH reaction itself or are due to radiation and drugs used to prepare the host for transplantation. GVH reactions were induced by intravenously infusing 50 x 50(6) lymph node and spleen cells from A/J-strain donors into (C57BL/6 x A/J)F1-hybrid recipients. These mice developed an active inflammatory myopathy beginning 15 days after engraftment. The inflammatory infiltrates were focal in distribution, initially around perimysial blood vessels, and later around muscle fibers. The infiltrating cell population was composed of lymphocytes, plasmacytoid cells, and macrophages. Muscle cell necrosis was observed and was temporally related to elevations in serum creatine kinase. Similar histologic changes were present in the myocardium. Our findings support the notion that muscle involvement in patients with GVH disease is caused by the disease itself. Myositis accompanying experimental GVH disease in mice may hold promise as a model of autoimmune inflammatory myopathy.

An analysis of pulmonary natural killer cell activity in F1-hybrid mice with acute graft-versus-host reactions.

The kinetics of activation, cell surface phenotype, target cell specificity and anatomic localization of pulmonary natural killer cells was examined in (C57BL/6 X A/J)F1-hybrid mice with acute graft-versus-host reactions induced by intravenous injection of 50 x 10(6) parental strain lymph node and spleen cells. Results showed that there was a marked increase in NK cell activity directed against YAC-1 tumor cells. This activity remained elevated in the lung over almost the entire course of the reaction, whereas it was only transiently increased in the spleen during the early stages of the reaction and then fell to control values. During the reaction, NK cells from both organs acquired the ability to kill P815 targets, cells that are normally insensitive to NK cell lysis. The level of P815 killing never reached that achieved against YAC-1 cells, but was significantly higher in the lung than in the spleen. Antibody and complement depletion experiments showed that both anti-YAC-1 and anti-P815 activity could be depleted with antiserum to the asialo-GM1 cell surface marker, but was unaffected by anti-Lyt-1.2 and anti-Lyt-2.2 treatment. Anti-YAC-1 activity was partly sensitive to depletion with anti-Thy-1.2. Cytotoxicity to P815 target cells acquired during the reaction was completely abrogated by anti-Thy-1.2. These findings suggest that during the reaction two phenotypically distinct types of NK cells are activated: a conventional, Thy-1-negative cell that kills only YAC-1 targets, and a Thy-1-positive cell with a broadened spectrum of lytic activity. We suggest that the latter may be generated in response to interleukin-2 released during the lymphoproliferative phase of the reaction and may represent a type of lymphokine-activated killer cell. Our results revealed that virtually all of the NK cell activity in the lung could be attributed to cells residing in the interstitium, or to cells tightly adherent to endothelium or epithelium. There was no correlation between augmented NK cell activity in the lung and the presence of peribronchial and perivascular mononuclear cell infiltrates seen in histological sections of the lung. These findings do not appear to support the idea that NK cells are by themselves directly responsible for the pathological changes produced by the reaction.