Introduction: Pulmonary arterial hypertension (PAH) is a disease with high mortality and limited therapeutic options. It is characterized by a progressive pulmonary vascular remodeling, although the mechanisms responsible for initiation of the proliferative phenotype are still undetermined. The receptor for advanced glycation endproducts (RAGE) was shown to be strongly overexpressed in lungs of PAH patients. RAGE activates by damage associated molecular patterns (DAMP) and induces proliferation through mechanisms that are not well characterized.
Hypothesis: We hypothesized that RAGE plays an important role in the transition of an initial pulmonary vascular damage to uncontrolled proliferation and, thus, promotes PAH.
Methods: 32 female SD rats were injected with 50mg/kg of Su5416 and exposed to 3 weeks of hypoxia and 2 weeks of normoxia. RAGE was immunoprecipitated from lungs and analyzed for a protein interactome using immunoblotting and mass spectrometry.
Results: Right ventricle systolic pressure was significantly increased in PAH rats (56.5±3.2, 69.4±5.1 and 113.3±5.9 mmHg at week 1, 2 and 5 respectively vs. 25.6±1.3 mmHg in Control, N=5-8). We also found a strong remodeling of small and larger pulmonary arteries that progressed with the disease. PAH increased interaction of RAGE with the DAMP molecule HMGB1 and an adaptor protein MYD88. Moreover, a PAH-mediated early glycolytic shift, evidenced by the accumulation of glucose-6-phophate (G6P, 4.6±1 vs 0.9±0.5 pg/μg of protein in Sugen1wk vs Control lungs, N=3) was associated with the formation of never described before RAGE/IMPA1 complex. IMPA1 is an enzyme that protects cells from osmotic stress induced by G6P through its conversion to non-osmotic myo-inositol. Since IMPA1 is involved in inositol’s production, we evaluated whether there was any increase in activity of Akt, which is inositol-3-phosphate dependent. Indeed, there was a strong accumulation of pS473Akt and pT308Akt in the membrane fraction correlated with the level of RAGE/IMPA1 interaction.
Conclusions: This is the very first evidence that damage induced RAGE activation is involved in protection from glycolysis-mediated osmotic stress and activation of the Akt pathway by the formation of a RAGE/IMPA1 complex.