Apoptosis Chemotaxis Cotinine Extracellular Traps Flow Cytometry Gene Expression Humans Neutrophils Nicotine Reactive Oxygen Species Real-Time Polymerase Chain Reaction Smoke Smoking Thiocyanates apoptosis chemotaxis cigarette smoke cotinine drug effect extracellular trap flow cytometry gene expression human inflammation metabolism neutrophil neutrophils nicotine periodontitis reactive oxygen metabolite