A_2A adenosine receptor (A_2AAR) has potent anti-inflammatory properties, which may be important in the regulation of airway reactivity and inflammation. Inflammatory cells that possess A_2AAR also produce nitrosative stress which is associated with pathophysiology of asthma, so we hypothesized that A_2AAR deficiency may lead to increased airway reactivity and inflammation through nitrosative stress. Thus, the present study was carried out to investigate the role of A_2AAR on airway reactivity, inflammation, nuclear factor kappa B (NF-kB) signaling and nitrosative stress in A_2A AR knock-out (KO) and wild-type (WT) mice using our murine model of asthma. Animals were sensitized i.p. on days 1 and 6 with 200µg of ragweed, followed by aerosolized challenges with 0.5% ragweed on days 11, 12 and 13, twice a day. On day 14, airway reactivity to methacholine was assessed as enhanced pause (Penh) using whole body plethysmography followed by bronchoalveolar lavage (BAL) and lung collection for various analyses. Allergen challenge caused significant decrease in expression of A_2AAR in A_2AWT sensitized mice, with A_2AAR expression being undetected in A_2AKO sensitized group leading to decreased lung cAMP levels in both groups. A_2AAR deletion/downregulation led to an increase in Penh to methacholine and influx of total cells, eosinophils, lymphocytes and neutrophils in BAL with highest values in A_2AKO sensitized group. A_2AKO sensitized group further had increased NF-kB expression and nitrosative stress as compared to WT sensitized group. These data suggest that A_2AAR deficiency leads to airway inflammation and AHR, possibly via involvement of nitrosative stress in this model of asthma.