Abstract
Direct delivery of chemotherapeutic agents to the lung can increase both the drug concentration and exposure period to lung tumours. The objective of this study was to formulate docetaxel (DOC) into a metered dose inhaler (MDI), assess its aerodynamic characteristics and to evaluate the effect of celecoxib (CXB), a cyclooxygenase-2 (COX-2) inhibitor, on the in-vitro cytotoxicity and apoptotic response of aerosolized DOC against human lung adenocarcinoma cell line A549. A stable solution-type MDI formulation was developed with 0.25% DOC and 15% w/w ethyl alcohol using HFA 134a propellant. The formulation was evaluated for medication delivery, mass median aerodynamic diameter (MMAD), geometric standard deviation (GSD), percent throat deposition, respirable mass and respirable fraction. A six-stage viable impactor was used to assess the in-vitro cytotoxicity of DOC-MDI alone or in combination with CXB. Induction of apoptosis in A549 cells by DOC (non-aerosolized and aerosolized) in combination with CXB was evaluated by established techniques, such as caspase-3 estimation and terminal deoxynucleotidyl transferase-mediated nick end labelling (TUNEL) staining. The influence of different treatments on the expression of COX-2 and peroxisome proliferator-activated receptor-gamma(PPAR-gamma) in A549 cells was studied by RT-PCR. The DOC-MDI formulation had a MMAD of 1.58 microm, (GSD = 3.2) and a medication delivery of 80 microg/shot. DOC-MDI (one shot) in combination with CXB (10 microg mL(-1)) had a cell kill of more than 80% as determined by in-vitro cytotoxicity assay. The specific caspase-3 activity in A549 cells treated with DOC (0.01 microg mL(-1)) and CXB (10.0 microg mL(-1)) combination was 4 times higher than CXB and untreated control group, respectively. Further, TUNEL staining showed significant apoptosis of A549 cells treated with aerosolized DOC alone or in combination with CXB when compared with CXB and untreated cells. The RT-PCR experiments showed similar expression of COX-2 in both control and treated groups. PPAR-gamma expression was increased in the combination treatment (0.01 microg mL(-1) DOC and 10 microg mL(-1) CXB) as compared with control (untreated), DOC (0.01 microg mL(-1)) and CXB (10 microg mL(-1)) treatments. Our results indicate the potential of inhalation delivery of DOC in the treatment of lung cancer.
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