Tumor necrosis factor-alpha serum levels in healthy smokers and nonsmokers

Tobacco smoking is the most important risk factor for chronic obstructive pulmonary disease (COPD) development. Inhaled cigarette smoke can induce tumor necrosis factor-alpha (TNF-alpha) production by alveolar macrophages, which in turn may enhance the production of metalloproteinases (MMPs). MMPs have been involved in mediating airway inflammation and lung destruction.

We aimed to measure the TNF-alpha serum levels in healthy heavy smokers and healthy nonsmokers to determine the dose-response relationship based on the cigarette smoke exposure.

We included in our study 43 healthy heavy smokers and 19 healthy nonsmokers (the control group). The smokers group was classified as less than one pack, one pack, and more than one pack per day. A clinical and paraclinical evaluation was performed in both groups, without any evidence of infection or COPD. The serum levels of TNF-alpha were assessed by ELISA.

The TNF-alpha serum levels were significantly higher for the group of smokers compared to the group of nonsmokers (P < 0.004). We also noticed an increased TNF-alpha concentration in the serum of smokers with more than one pack per day compared with those with less than one pack per day (P < 0.03). There was a positive correlation between the serum level of TNF-alpha and tobacco smoke exposure.

The high levels of TNF-alpha in the serum of smokers suggest an imbalance between the proinflammatory and anti-inflammatory factors as a result of tobacco smoke exposure. The concentration of TNF-alpha is elevated in the serum of healthy heavy smokers in a cigarette dose-dependent manner. We speculate that the serum level of TNF-alpha might be a useful biomarker for the selection of heavy smokers with a high risk of developing smoke induced pulmonary diseases.