Desmin Preamyloid Oligomers in Experimental Heart Failure and Cultured Cardiac Myocytes

Background: Heart Failure (HF) is one of the main causes of morbidity and mortality in westernized countries but the molecular mechanisms underlying its development are still unclear. A paradigm-shifting view focuses on the accumulation of preamyloid oligomers (PAOs), similar to those observed in Alzheimer disease, as a potential mechanism of cardiac toxicity. We reported that differential desmin phosphorylation at serines (S) 27 and 31 could drive the formation of PAOs in the heart, in the absence of genetic mutations. We sought to establish the identity of the molecular seed triggering the nucleation of cardiac PAOs in an experimental model of HF and in cultured cardiac cells. Methods: Mice were subjected to transverse aortic constriction (TAC) for 4 weeks (FS% = 29.3±2.6, P=0.0001). Alternatively, neonatal rat ventricular myocytes were transduced with lentiviral vectors carrying alanine (A) or phospho-mimetic aspartate (D) desmin double mutants at S27 and S31, fused with GFP. Protein homogenates were subjected to western blot analysis with fluorescent co-staining using the A11 anti-PAOs and anti-desmin antibodies. Transduced cells were also subjected to live imaging to assess phenotype. Results: Co-western blot analysis of both TAC mice and phospho-mimetic mutant cells revealed the colocalization of PAOs with desmin modified (potentially cleaved) forms. Preamyloid oligomers and a desmin fragment were both increased in TAC mice vs. controls (2.8-fold, P=0.023 and 1.8-fold, P=0.038, respectively). The DD mutant, mimicking the doubly phosphorylated desmin that we hypothesized is the physiological form, showed a healthier phenotype in terms of number of spontaneously contracting cells (P=0.041) and incorporation of GFP-desmin at the Z-discs (P=0.0027), whereas the mono-phosphomimetic mutant (AD) resulted in the increase of desmin positive aggregates (P=0.0014). Conclusions: This preliminary evidence suggests that desmin modified forms represent the seed triggering the formation of cardiac PAOs, in the absence of genetic mutations. The accumulation of desmin PAOs could therefore represent an overarching mechanism underlying the deterioration of cardiac function in HF.