Enhanced VEGFR-1 signalling is involved in Cu regression of cardiomyocyte hypertrophy, and the PKG-1 pathway is likely associated with VEGFR-1.

Dietary copper supplementation reverses the pressure overload-induced cardiac hypertrophy. Activation of vascular endothelial growth factor receptor-1 (VEGFR-1) and cyclic guanosine monophosphate (cGMP)-dependent protein kinase-1 (PKG-1) is required for the regression. The present study was undertaken to determine the link between VEGFR-1 and PKG-1 in copper regression of cardiomyocyte hypertrophy. Human cardiac myocytes (HCM) or primary cultures of neonatal rat cardiomyocytes were exposed to phenylephrine (PE) at a final concentration of 100 μM for 48 h to induce cell hypertrophy. Copper sulfite was added to cultures of hypertrophic cardiomyocytes at a final concentration of 5 μM elemental copper and incubated for 24 h to reverse cell hypertrophy. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis identified a 56 kDa copper-binding protein, vimentin, which was co-immunoprecipitated with VEGFR-1 and PKG-1. Copper supplementation increased vimentin levels and enhanced PKG-1 activity. Gene silencing using siRNA targeting vimentin prevented copper-induced elevation of vimentin, depressed the activity of PKG-1, and blocked the copper-induced regression of cardiomyocyte hypertrophy. This study demonstrates that vimentin is critically involved in the VEGFR-1 mediated activation of the PKG-1 signaling pathway, leading to regression of cardiomyocyte hypertrophy.

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Breast cancer is a leading cause of cancer death among women in the United States. Arylamine N‐acetyltransferase 1 (NAT1) has been linked to breast cancer because of its role in the metabolic activation and detoxification of carcinogens. However, recent studies suggest it may play an important role in cancer biology. Higher NAT1 expression is associated with more aggressive cancers and poorer prognosis. Increased NAT1 levels in primary tumors are significantly associated with increased metastasis to the bone. We have observed NAT1 inhibition decreased proliferation and invasiveness of MDA‐MB‐231 breast cancer cells. To delineate the mechanisms by which NAT1 inhibition decreases cell invasion and proliferation, MDA‐MB‐231 and MCF‐7 breast cancer cell lines were treated with siRNA targeting NAT1, or a non‐targeting siRNA. Cells were collected at 24, 48, 72 and 96 hours after treatment. In vitro assays using a NAT1‐specific substrate, para‐aminobenzoic acid (PABA) were conducted to measure NAT1 activity by HPLC. NAT1 mRNA was measured using qRT‐PCR. Optimal knockdown of NAT1 occurred at 96 and 72 hours in MCF‐7 and MDA‐MB‐231 cells, with 65% (p < 0.005) of NAT1 activity remaining after treatment in both cell lines. NAT1 mRNA decreased 60% (p < 0.0001) and 34% (p < 0.001) in MCF‐7 and MDA‐MB‐231 cells, respectively. These samples will undergo whole genome analysis using a GeneArray to identify potential gene expression signatures which may be altered as a result of NAT1 inhibition. [Partially supported by NIEHS T32‐ESO11564]