Abstract Body (Do not enter title and authors here): Background:
We have previously demonstrated that diabetes mellitus (DM) causes cardiac inflammation leading to heart failure with preserved ejection fraction (HFpEF). Arachidonate 5-lipoxygenase (5-LOX), encoded by the ALOX5 gene, is an enzyme that is highly expressed in leukocytes. 5-LOX synthesizes specialized pro-resolving mediators (SPMs) including Resolvin D1 (RvD1), which reduce inflammation.
Hypothesis:
We hypothesize that cardiac-specific ALOX5 upregulation could prevent diabetes-associated HFpEF without inducing systemic immunosuppression.
Methods:
DM was induced by feeding mice with a high fat diet (HFD, 60% fat by kcal) starting from 6 weeks of age for 22-24 weeks. At 24 weeks of age, DM mice were treated with RvD1, by intraperitoneal injection at 100 ng/mouse for 2 weeks. To specifically upregulate 5-LOX in the heart, another cohort of DM mice were injected with either AAV9-plain or AAV9-ALOX5 viral vectors under the control of the α-myosin heavy chain (MHC) at 22 weeks old. At 28 weeks, we performed echocardiographic measurement of diastolic function and heart extraction.
Results:
HFD-induced DM mice showed lower cardiac 5-LOX expression (0.72 ± 0.05 a.u. vs. 1.09 ± 0.12, p < 0.05) and RvD1 levels (1 ± 0.08 vs. 1.9 ± 0.14 fold change over DM mice, p<0.0001) than the mice with normal diet. RvD1 treatment significantly improved DM-associated diastolic function (19.7 ± 1.4 a.u. vs. 22.9 ± 0.4, p<0.05). With cardiac specific upregulation of 5-LOX, cardiac 5-LOX expression (0.89 ± 0.06 vs. 0.70 ± 0.04 a.u., p<0.05) and RvD1 levels were increased (2.1 ± 0.3 a.u. vs. 1.2 ± 0.2, normalized to AAV9-plain, p<0.05). AAV9-ALOX5 also reduced NLRP3 inflammasome activity (0.80 ± 0.02 a.u. vs. 0.90 ± 0.02, p<0.01) and improved DM-associated diastolic dysfunction (17.0 ± 1.2 a.u. vs. 20.5 ± 1.0, p<0.05) without affecting glucose metabolism and obesity in DM mice. Moreover, no alterations of cardiac macrophage infiltration, inflammatory IL1β signaling, or macrophage phenotype were observed in response to cardiac-specific ALOX5 upregulation.
Conclusion:
In conclusion, both direct RvD1 treatment and cardiac-specific gene therapy to enhance resolution of inflammation in cardiomyocytes reversed DM-associated HFpEF. Gene therapy avoided off-target immunosuppression. Therefore, AAV-directed cardiac ALOX5 upregulation represents a novel cardiac-specific gene therapy for HFpEF that avoids systemic immunosuppression.