Circulating Factors Induce Cardiomyopathy after Burn Injury

Previous in vivo work has demonstrated that the phosphodiesterase type 5 (PDE5)-cyclic guanosine monophosphate-protein kinase G pathway is involved in burn-induced heart dysfunction. PDE5A inhibitors may reverse this dysfunction. It is unknown if circulating factors after burn injury can continue to damage cardiomyocytes and if this can be reversed by PDE5A inhibitors in vitro. This study hypothesized that circulating factors released after burn injury cause mitochondrial damage in cardiomyocytes in vitro.

Human cardiomyocyte cell line-AC16-was divided into 4 groups, which were treated with serum obtained from rats with sham injury, 24 hours post burn (24hpb), sildenafil (SIL) alone, and 24hpb treated with SIL. ELISA, mitochondrial function studies, fluorescence microscopy, gene analysis, and Illumina RNA sequencing were performed. GraphPad Prism 9.2.0 was used for statistical analysis.

Cyclic guanosine monophosphate levels were significantly decreased, and cTN1 levels were significantly increased in the 24hpb serum group. Treatment with SIL completely reversed this change, similar to our previous in vivo work. We observed that there was significantly decreased cell viability and cell proliferation and increased cell cytotoxicity, cell apoptosis, and cell reactive oxygen species production in the cells treated with 24hpb serum. Cells treated with 24hpb serum exhibited mitochondrial dysfunction, as demonstrated by decreased ATP production and compromised mitochondrial membrane integrity or potential, along with increased mitochondrial reactive oxygen species. Seahorse and O2K approaches confirmed 24hpb serum treated cardiomyocyte mitochondrial dysfunction as evidenced by decreases in mitochondrial basal respiration, proton leak, ATP production, and maximal respiration. SIL returned these responses to near sham levels.

This study provided data that may improve the understanding of mechanisms driving cardiac dysfunction after burn injury. Our study provided evidence for understanding the pathogenic mechanism of circulating factors released after burn injury.