Pressure overload induces overexpression of annexins II and V in aortic-banded rats

Proteomics approach to examine the cardiotoxic effects of Nemopilema nomurai Jellyfish venom

Nemopilema nomurai is one of the largest species of jellyfish in the world. It blooms mainly offshore of Korea, China, and Japan. Increasing population numbers of N. nomurai is increasing the risk of sea bathers to the jellyfish stings and accompanying envenomations. Cardiovascular effects, and cytotoxicity and hemolytic activities have been previously reported in rodent models. To understand the mechanism of cardiac toxicity, we examined the effect of N. nomurai jellyfish venom (NnV) at the proteome level on rat cardiomyocytes cell line H9c2 using two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS). Cells treated with NnV displayed dose-dependent inhibition of viability. Cellular changes at proteome level were investigated after 6h and 12h of venom treatment. Electrophoretic examination revealed 72 protein spots displaying significant quantitative changes. These proteins were analyzed by MALDI-TOF/MS. Thirty four differentially expressed proteins were successfully identified; 24 proteins increased in quantity and 10 proteins decreased, compared to the respective controls. Proteins altered in content in Western blot analyses included myosin VII, annexin A2, aldose reductase, suppressor of cytokine signaling 1 (SOCS1), and calumenin, which are well-known marker proteins of cardiac dysfunctions.

BIOLOGICAL SIGNIFICANCE

This is the first report revealing the cardiac toxicity of NnV at the proteome level. NnV directly targeted proteins involved in cardiac dysfunction or maintenance. Suppressor of cytokine signaling 1 (SOCS1), which inhibits the Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway, was upregulated by NnV. Other proteins related to cardiac arrest that were over-expressed included aldose reductase and calumenin. These results clarify the underlying mechanism of cardiomyocyte damage caused by NnV. By inhibiting these particular targets and more precisely identifying the components of NnV-mediated cardiac toxicity, jellyfish venom-associated poisoning could be reduced or prevented.

The tumor suppressor gene PTEN can regulate cardiac hypertrophy and survival

Cardiac hypertrophy is a complex process involving the coordinated actions of many genes. In a high throughput screen designed to identify transcripts that are actively translated during cardiac hypertrophy, we identified a number of genes with established links to hypertrophy, including those coding for Sp3, c-Jun, annexin II, cathepsin B, and HB-EGF, thus showing the general utility of the screen. Focusing on a candidate transcript that has not been previously linked to hypertrophy, we found that protein levels of the tumor suppressor PTEN (phosphatase and tensin homologue on chromosome ten) were increased in the absence of increased messenger RNA levels. Increased PTEN expression by recombinant adenovirus in cultured neonatal rat primary cardiomyocytes caused cardiomyocyte apoptosis as evidenced by increased caspase-3 activity and cleaved poly(A)DP-ribose polymerase. Expression of PTEN was also able to block growth factor signaling through the phosphatidylinositol 3,4,5-triphosphate pathway. Surprisingly, expression of a catalytically inactive PTEN mutant led to cardiomyocyte hypertrophy, with increased protein synthesis, cell surface area, and atrial natriuretic factor expression. This hypertrophy was accompanied by an increase in Akt activity and improved cell viability in culture.