Efficacy of atropine and scopolamine on airway contractions following exposure to the nerve agent VX.

Nerve agents are highly toxic organophosphorus compounds that inhibit acetylcholinesterase resulting in rapid accumulation of the neurotransmitter acetylcholine (ACh) causing a cholinergic syndrome including respiratory failure. In the present study, respiratory responses and antimuscarinic treatment efficacy was evaluated ex vivo using rat precision-cut lung slices (PCLS) exposed to the nerve agent VX. The respiratory effects were evaluated either by adding exogenous ACh directly to the culture medium or by applying electric-field stimulation (EFS) to the PCLS to achieve a release of endogenous ACh from neurons in the lung tissue. The airway contraction induced by both methods was enhanced by VX and resulted in lingering airway recovery, in particular when airways were exposed to a high VX-dose. Both contractions induced by EFS and exogenously added ACh were significantly reduced by administration of the antimuscarinic drugs atropine or scopolamine. Two additions of atropine or scopolamine after maximal ACh-induced airway response was demonstrated effective to reverse the contraction. By adding consecutive doubled doses of antimuscarinics, high efficiency to reduce the cholinergic airway response was observed. However, the airways were not completely recovered by atropine or scopolamine, indicating that non-muscarinic mechanisms were involved in the smooth muscle contractions. In conclusion, it was demonstrated that antimuscarinic treatment reversed airway contraction induced by VX but supplemental pharmacological interventions are needed to fully recover the airways. Further studies should therefore clarify the mechanisms of physiological responses in lung tissue following nerve agent exposures to improve the medical management of poisoned individuals.

Differential anti-inflammatory and anti-oxidative effects of dexamethasone and N-acetylcysteine in endotoxin-induced lung inflammation.

Inhalation of bacterial endotoxin induces an acute inflammation in the lower respiratory tract. In this study, the anti-inflammatory effects of the anti-oxidant N-acetylcysteine (NAC) and the glucocorticoid dexamethasone were investigated in mice exposed to aerosolized endotoxin (lipopolysaccharide (LPS)). Powerful reduction of neutrophils in bronchoalveolar lavage fluid (BALF) was obtained by a single i.p. injection of dexamethasone (10 mg/kg), whereas treatment with NAC only resulted in reduction of neutrophils when administered at a high dose (500 mg/kg). Measurement of cytokine and chemokine expression in lung tissue revealed a significant decrease of tumour necrosis factor-alpha, IL-1alpha, IL-1beta IL-6, IL- 12p40, and MIP-1alpha mRNA when mice where treated with dexamethasone but not when treated with NAC. Analysis of oxidative burst demonstrated a remarkable reduction of oxygen radicals in BALF neutrophils after treatment with dexamethasone, whereas the effect of NAC was not significantly different from that in untreated animals. In conclusion, dexamethasone exerted both anti-inflammatory and anti-oxidative effects in acute airway inflammation, probably by blocking early events in the inflammatory cascade. In contrast, treatment with NAC resulted in a weak reduction of the inflammatory response but no inhibition of proinflammatory cytokines or reduction of oxidative burst in neutrophils. These results demonstrate dramatic differences in efficiency and also indicate that the two drugs have different actions. Combined treatment with NAC and dexamethasone revealed an additive action but no synergy was observed.

The endogenous adjuvant squalene can induce a chronic T-cell-mediated arthritis in rats.

Squalene is a cholesterol precursor, which stimulates the immune system nonspecifically. We demonstrate that one intradermal injection of this adjuvant lipid can induce joint-specific inflammation in arthritis-prone DA rats. Histopathological and immunohistochemical analyses revealed erosion of bone and cartilage, and that development of polyarthritis coincided with infiltration of alphabeta(+) T cells. Depletion of these cells with anti-alphabeta TcR monoclonal antibody (R73) resulted in complete recovery, whereas anti-CD8 and anti-gammadelta TcR injections were ineffective. The apparent dependence on CD4(+) T cells suggested a role for genes within the major histocompatibility complex (MHC), and this was concluded from comparative studies of MHC congenic rat strains, in which DA.1H rats were less susceptible than DA rats. Furthermore, LEW.1AV1 and PVG.1AV1 rats with MHC identical to DA rats were arthritis-resistant, demonstrating that non-MHC genes also determine susceptibility. Some of these genetic influences could be linked to previously described arthritis susceptibility loci in an F2 intercross between DA and LEW.1AV1 rats (ie, Cia3, Oia2 and Cia5). Interestingly, some F2 hybrid rats developed chronic arthritis, a phenotype not apparent in the parental inbred strains. Our demonstration that an autoadjuvant can trigger chronic, immune-mediated joint-specific inflammation may give clues to the pathogenesis of rheumatoid arthritis, and it raises new questions concerning the role of endogenous molecules with adjuvant properties in chronic inflammatory diseases.

CD8+ cells suppress oil-induced arthritis.

Oil-induced arthritis is a genetically restricted polyarthritis that develops in the DA rat after injection of the mineral oil Freund's incomplete adjuvant. Here, we investigated the role of the potentially disease-limiting cell populations CD8+ T cells, gammadelta T cells, natural killer (NK) cells and NK T cells in inguinal lymph nodes for the development of this adjuvant-induced arthritis. Flow cytometry analysis before and at disease onset revealed a higher proportion of lymph node T cells expressing NKR-P1 in the disease-resistant LEW.1AV1 compared with the disease-susceptible DA strain, suggesting that NK T cells might be disease protective. However, prophylactic in vivo administration of an anti-NKR-P1 MoAb (clone 10/78) did not consistently affect the disease course. The proportion of CD8+ T cells and the ratio CD4+/CD8+ T cells in inguinal lymph nodes did not differ significantly between DA and LEW.1AV1 rats before or at disease onset. Nevertheless, prophylactic in vivo depletion of CD8+ cells by the OX8 MoAb in the DA strain resulted in an earlier disease onset compared with the control group, demonstrating that CD8+ cells regulate arthritis development. In vivo depletion of gammadelta T cells by the V65 MoAb did not alter the disease course, indicating that the disease-suppressive CD8+ cells are alphabeta T cells or NK cells.