Lactate dehydrogenase and caspase activity in nasopharyngeal secretions are predictors of bronchiolitis severity

Mehta, Reena; Scheffler, Margaret; Tapia, Lorena; Aideyan, Letisha; Patel, Kirtida D; Jewell, Alan M; Avadhanula, Vasanthi; Mei, Minghua; Garofalo, Roberto P; Piedra, Pedro A

Caspase 3/7 activity is a marker of apoptosis. Caspase 3/7 activity was measured in NPA samples using the Caspase-Glo-3/7 kit (Promega, Madison, WI, USA). The assay generates luminescent activity proportional to caspase activity. Luminescence was measured with a FLUOstar OPTIMA microplate reader (BMG Labtech, Cary, NC, USA) and expressed in relative luminescence units. To calculate relative units (U/l) of caspase activity, a standard curve using recombinant human caspase-3 protein (R&D Systems, Minneapolis, MN, USA) was used demonstrating an ample linear dynamic range of activity at the dilutions tested (20 000-32 U/l). The value was expressed as relative units and it was assumed that one unit of caspase activity was equal to 0Á1 ng of protein. It is important to note that caspase 3 activity can vary from lot to lot.