Inhaled combination of sildenafil and rosiglitazone improves pulmonary hemodynamics, cardiac function, and arterial remodeling

Abstract

Currently, dual- or triple-drug combinations comprising different vasodilators are the mainstay for the treatment of pulmonary arterial hypertension (PAH). However, the patient outcome continues to be disappointing because the existing combination therapy cannot restrain progression of the disease. Previously, we have shown that when given as a monotherapy, long-acting inhaled formulations of sildenafil (a phosphodiesterase-5 inhibitor) and rosiglitazone (a peroxisome proliferator receptor-γ agonist) ameliorate PAH in rats. Thus, with a goal to develop a new combination therapy, we prepared and characterized poly(lactic-co-glycolic acid) (PLGA)-based long-acting inhalable particles of sildenafil and rosiglitazone. We then assessed the efficacy of the combinations of sildenafil and rosiglitazone, given in plain forms or as PLGA particles, in reducing mean pulmonary arterial pressure (mPAP) and improving pulmonary arterial remodeling and right ventricular hypertrophy (RVH) in Sugen 5416 plus hypoxia-induced PAH rats. After intratracheal administration of the formulations, we catheterized the rats and measured mPAP, cardiac output, total pulmonary resistance, and RVH. We also conducted morphometric studies using lung tissue samples and assessed the degree of muscularization, the arterial medial wall thickening, and the extent of collagen deposition. Compared with the plain drugs, given via the pulmonary or oral route as a single or dual combination, PLGA particles of the drugs, although given at a longer dosing interval compared with the plain drugs, caused more pronounced reduction in mPAP without affecting mean systemic pressure, improved cardiac function, slowed down right heart remodeling, and reduced arterial muscularization. Overall, PLGA particles of sildenafil and rosiglitazone, given as an inhaled combination, could be a viable alternative to currently available vasodilator-based combination therapy for PAH.

Keywords: arterial remodeling; inhalation delivery; pulmonary arterial hypertension; right ventricular hypertrophy; rosiglitazone; sildenafil.

Fig. 1.

Protocol for the development of pulmonary arterial hypertension in rats: study design and various treatment groups. IT, intratracheal; RV, right ventricle.

Fig. 2.

Effect of plain drugs or formulations on mean pulmonary arterial pressure (A) and mean systemic arterial pressure (B). Data represent means ± SE. IT, intratracheal; MP, microparticles; Ros, rosiglitazone; Sil, sildenafil; Data were analyzed using one-way ANOVA followed by Fisher’s least significant difference test; n = 3–4, *P < 0.05.

Fig. 3.

A: representative pressure-volume loops from each treatment group. B and C: efficacy of plain drugs or formulations in improving cardiac functional parameters: cardiac index (B) and total pulmonary vascular resistance (C). Data represent means ± SE. IT, intratracheal; LV, left ventricle; MP, microparticles; Ros, rosiglitazone; Sil, sildenafil. Data were analyzed using one-way ANOVA followed by Fisher’s least significant difference test; n = 3–4, *P < 0.05.

Fig. 4.

Effect of various treatments on right ventricle (RV)-to-left ventricle (LV) plus septum ratio, a direct measure of right heart remodeling in pulmonary arterial hypertension. Data represent means ± SE. IT, intratracheal; MP, microparticles; Ros, rosiglitazone; Sil, sildenafil. Data were analyzed by one-way ANOVA followed by Fisher’s least significant difference test; n = 3–4, *P < 0.05.

Fig. 5.

A: representative microphotographs of the muscularized arteries of rats treated with plain drugs and formulations. B and C: effect of the drugs or formulations on arterial medial wall thickening (B) and extent of muscularized pulmonary arteries (C). IT, intratracheal; MP, microparticles; Ros, rosiglitazone; Sil, sildenafil. Data were analyzed using one-way ANOVA followed by Fisher’s least significant difference test; n = 3–4, *P < 0.05.

Fig. 6.

A: representative micrographs of the pulmonary arteries stained for the presence or absence of collagen. B: extent of collagen deposition. Data represent means ± SE; n = 3–4. IT, intratracheal; MP, microparticles; Ros, rosiglitazone; Sil, sildenafil.