Lung Transplant Immunosuppressive Drugs Influence Pulmonary Surfactant Protein A (SP-A) Expression

Purpose: Pulmonary surfactant protein A (SP-A) contributes to innate host defense serving as an opsonin, regulating phospholipid homeostasis, and regulating pulmonary innate and adaptive immune response. SP-A is a polymer encoded by two genes, SP-A1 and SP-A2. We studied the influence of lung transplant immunosuppressive drugs on SP-A expression. Methods and Materials: NCI-H441 human cell cultures have been incubated for 24Hrs using incremental doses of methylprednisolone, tacrolimus, or sirolimus (10-5,..-10 M). SP-A1 and SP-A2 mRNA and SP-A protein expression were assayed respectively by real time RT-PCR and Western blot. Results were analyzed using a mixed model for SP-A expression as a function of drug concentration adjusting for GADPH (endo-gene/protein) expression. Results: Real time RT-PCR showed that: methylprednisolone at high concentrations (10-5M, 10-6M) decreased SP-A1 and SP-A2 mRNA expression as compared to control and to low steroid concentration (10-7M-10-9M) (p<0.005); tacrolimus provided variation of SP-A2 mRNA expression by drug concentration; Sirolimus at high concentrations (5-8M, 10-7M) increased SP-A1 mRNA expression (p<0.05). Western blot revealed that methylprednisolone at high concentrations (10-5M median absorbance 0, IQ-range 0-0.005, and 10-6M median 0.002, IQ-range 0-0.009) decreased SP-A protein expression levels compared to control (median 0.95, IQrange 0.65-1.27) (p<0.05). No difference was noted for tacrolimus and sirolimus.