N-Octanoyl Dopamine Treatment of Endothelial Cells Induces the Unfolded Protein Response and Results in Hypometabolism and Tolerance to Hypothermia

Abstract

AimN-acyl dopamines (NADD) are gaining attention in the field of inflammatory and neurological disorders. Due to their hydrophobicity, NADD may have access to the endoplasmic reticulum (ER). We therefore investigated if NADD induce the unfolded protein response (UPR) and if this in turn influences cell behaviour.MethodsGenome wide gene expression profiling, confirmatory qPCR and reporter assays were employed on human umbilical vein endothelial cells (HUVEC) to validate induction of UPR target genes and UPR sensor activation by N-octanoyl dopamine (NOD). Intracellular ATP, apoptosis and induction of thermotolerance were used as functional parameters to assess adaptation of HUVEC.ResultsNOD, but not dopamine dose dependently induces the UPR. This was also found for other synthetic NADD. Induction of the UPR was dependent on the redox activity of NADD and was not caused by selective activation of a particular UPR sensor. UPR induction did not result in cell apoptosis, yet NOD strongly impaired cell proliferation by attenuation of cells in the S-G2/M phase. Long-term treatment of HUVEC with low NOD concentration showed decreased intracellular ATP concentration paralleled with activation of AMPK. These cells were significantly more resistant to cold inflicted injury.ConclusionsWe provide for the first time evidence that NADD induce the UPR in vitro. It remains to be assessed if UPR induction is causally associated with hypometabolism and thermotolerance. Further pharmacokinetic studies are warranted to address if the NADD concentrations used in vitro can be obtained in vivo and if this in turn shows therapeutic efficacy.

N-acyl dopamine derivates as lead compound for implementation in transplantation medicine

“…NOD and N-pivaloyl dopamine. Recently, Stamellou et al reported that these synthetic NADD transiently activate the unfolded protein response (UPR) in endothelial cells [38]. This property is again dependent on the redox activity of these compounds.…”

“…This property is again dependent on the redox activity of these compounds. Although persistent activation of the UPR may result in apoptosis, the synthetic NADD did not affect cell viability in a μM range, yet they strongly impaired proliferation of endothelial cells [38] and smooth muscle cells [unpublished data]. Interestingly, Stamellou et al also demonstrated that long-term treatment of endothelial cells with synthetic NADD results in hypometabolism and thermotolerance.…”

N-Octanoyl-Dopamine inhibits cytokine production in activated T-cells and diminishes MHC-class-II expression as well as adhesion molecules in IFNγ-stimulated endothelial cells

“…While the catechol structure provides NOD with strong antioxidant properties, the hydrophobic fatty acid of NOD might allow its passage across membranes to access different intra-cellular compartments and change the redox milieu within these compartments. As such NOD may impair oxidative protein folding in the endoplasmic reticulum (ER) and consequently induce the unfolded protein response (UPR) 42,43 , or inhibit redox dependent transcription factors in the nucleus, e.g. NF-κB, AP-1 and NFAT 22 .…”

N-octanoyl Dopamine Attenuates the Development of Transplant Vasculopathy in Rat Aortic Allografts Via Smooth Muscle Cell Protective Mechanisms

“…However, loss of αSMA expression could be linked to phenotypic modulation and not necessarily to apoptosis. Chin et al 48 showed that metformin reduces I/R-injury and TV and suggested an adenosine monophosphate-activated protein kinase (AMPK) dependent mechanism that results in a lower apoptosis rate. We recently demonstrated that NOD activates AMPK, yet both NOD and metformin can act as antioxidants 49 and therefore this precludes drawing firm conclusions as to whether the antiapoptotic effect of both compounds are exclusively mediated via AMPK activation.…”