Determining selectivity of drugs by quantitative two-dimensional gel analysis: A study of tenidap, piroxicam, and dexamethasone

In vitro pharmacologic measures of drug specificity are well established, i.e. drug interaction with a specific target such as an enzyme, receptor, or ion channel. However, in vitro measures of drug selectivity, defined as effects on secondary targets, are lacking. Two-dimensional gel electrophoresis (2-D gel) was examined as a measure of drug selectivity by comparing the effects of three drugs, tenidap, piroxicam, and dexamethasone, on the synthesis of intracellular proteins in lipopolysaccharide (LPS)-stimulated murine macrophages. A set of 902 35S-methionine-labeled proteins were separated consistently, identified by their coordinates of apparent isoelectric point and molecular weight, and quantified. LPS altered the concentrations of 45 proteins. Tenidap, at 10 μM, affected a total of five proteins (suppressed three; stimulated two), whereas piroxicam, at 10 μM, suppressed two proteins. Dexamethasone at 0.01 μM suppressed eight proteins and stimulated one. Thus, none of the drugs reversed the LPS-induced changes. Two of the eight proteins suppressed by dexamethasone were also suppressed by tenidap and were identified as proIL-1α and proIL-1β. Since the subset of affected proteins provided a unique protein “fingerprint” for each drug, the three drugs were mechanistically differentiated by 2-D gel analysis. Compared to LPS (5% affected proteins), all three drugs were selective (⩽1% affected) with piroxicam > tenidap > dexamethasone. With identification of affected proteins, this technique can provide a useful in vitro assessment of drug selectivity.