Aim: Rosiglitazone is one of the specific PPARγ agonists showing potential therapeutic effects in asthma. Though PPARγ activation was considered protective in inhibiting airway inflammation and remodeling in asthma, the specific mechanisms are still unclear. This study was aimed to investigate whether heme oxygenase-1 (HO-1) related pathways were involved in rosiglitazone-activated PPARγ signaling in asthma treatment. Methods: Asthma was induced in mice by multiple exposures to ovalbumin (OVA) in 8 weeks. Prior to every OVA challenge, the mice received rosiglitazone (5 mg/kg, po). After the mice were sacrificed, the bronchoalveolar lavage fluid (BALF), blood samples and lungs were collected for analyses. The activities of HO-1, MMP-2 and MMP-9 in airway tissue were assessed, and the expression of PPARγ, HO-1 and p21 proteins was also examined. Results: Rosiglitazone administration significantly attenuated airway inflammation and remodeling in mice with OVA-induced asthma, which were evidenced by decreased counts of total cells, eosinophils and neutrophils, and decreased levels of IL-5 and IL-13 in BALF, and by decreased airway smooth muscle layer thickness and reduced airway collagen deposition. Furthermore, rosiglitazone administration significantly increased PPARγ, HO-1 and p21 expression and HO-1 activity, decreased MMP-2 and MMP-9 activities in airway tissue. All the therapeutic effects of rosiglitazone were significantly impaired by co-administration of the HO-1 inhibitor ZnPP. Conclusion: Rosiglitazone effectively attenuates airway inflammation and remodeling in OVA-induced asthma of mice by activating PPARγ/HO-1 signaling pathway.
Activation of peroxisome proliferator‐activated receptor (PPAR)‐γ suppresses proliferation of rat pulmonary artery smooth muscle cells (PASMCs), and therefore ameliorates the development of pulmonary hypertension in animal models. However, the molecular mechanisms underlying this effect remain largely unknown. This study addressed this issue. The PPARγ agonist rosiglitazone dose‐dependently stimulated heme oxygenase (HO)‐1 expression in PASMCs, 5 μm rosiglitazone inducing a 12.1‐fold increase in the HO‐1 protein level. Cells pre‐exposed to rosiglitazone showed a dose‐dependent reduction in proliferation in response to serotonin; this was abolished by pretransfection of cells with sequence‐specific small interfering RNA against HO‐1. In addition, rosiglitazone stimulated p21WAF1 expression in PASMCs, a 2.34‐fold increase in the p21WAF1 protein level being achieved with 5 μm rosiglitazone; again, this effect was blocked by knockdown of HO‐1. Like loss of HO‐1, loss of p21WAF1 through siRNA transfection also reversed the inhibitory effect of rosiglitazone on PASMC proliferation triggered by serotonin. Taken together, our findings suggest that activation of PPARγ induces HO‐1 expression, and that this in turn stimulates p21WAF1 expression to suppress PASMC proliferation. Our study also indicates that rosiglitazone, a medicine widely used in the treatment of type 2 diabetes mellitus, has potential benefits for patients with pulmonary hypertension.
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