Vascular inflammation inhibits gene transfer to the pulmonary circulation in vivo

We report gene transfer to the normal and injured murine pulmonary circulat ion via systemic (intravascular) and airway (intratracheal) delivery of nov el polycationic liposomes (imidazolium chloride, imidazolinium chloride-cho lesterol, and ethyl phosphocholine). With use of the reporter genes chloram phenicol acetyltransferase (CAT) or human placental alkaline phosphatase (h pAP), intravascular injection of lipid-DNA complexes resulted in gene expre ssion primarily in the lung, with lesser expression in the heart (11% of lu ng, P < 0.05) and spleen (8% of lung, P < 0.05). Histochemical staining for the hpAP reporter gene showed localized transgene expression in the microv ascular endothelium. Monocrotaline (80 mg/kg body wt sc) treatment produced endovascular inflammation and reduced lung CAT activity (2 days postintrav ascular transfection) by 75 +/- 8 and 86 +/- 6% at 7 and 21 days, respectiv ely, after monocrotaline (P < 0.05). Despite the apparent decrease in funct ional CAT protein, Southern blot analysis suggested maintained plasmid deli very whereas quantitative PCR (TaqMan) showed decreased CAT mRNA levels in monocrotaline mice. in contrast, intratracheal delivery of lipid-DNA comple xes showed enhanced CAT expression in monocrotaline mice. Transfection in a lternate pulmonary vascular disorders was studied by inducing hypoxic pulmo nary hypertension (4 wk at barometric pressure of 410 mmHg). Efficiency and duration of gene transfer, assessed by CAT activity, were similar in pulmo nary hypertensive and normal lungs. We conclude that imidazolinium-derived polycationic liposomes provide a means of relatively selective and efficien t gene transfer to the normal and injured murine microvascular circulation, although translation of transgene mRNA may be reduced by preexisting endot helial injury.