Metabolism Compound Library Our data demonstrate that MPO in

Our data demonstrate that MPO increased ETRB mRNA expression, which translated into an increase in ETRB protein expression, which proved to be dependent on the enzyme\'s catalytic activity. Of importance, addition of MPO was sufficient to increase ETRB expression, revealing that endogenous (endothelial cell and as well SMC)-derived H2O2 generation suffices to generate MPO-derived oxidants. Accordingly, MPO proved to mediate ETRB protein expression by activation of MAP kinases, which are also known to be involved in modulation of ETRB protein expression [35], [40], [41]. Uddman et al. [41] and Nilsson et al. [40] were able to demonstrate that induction of ETRB expression and ETRB-dependent vasoconstriction by organ culture of isolated vessels was attenuated by incubation with an inhibitor of the ERK1/2 or the p38 MAPK signaling pathway. Furthermore, Xu et al. [35] reported an attenuation of DMSO-soluble smoke particles-induced upregulation of ETRB-mediated contraction and mRNA and protein expression by inhibition of ERK1/2, p38 or NFκB signaling pathways. In accordance, we were able to show for MPO that inhibition of the ERK1/2 signaling pathways using PD98059 and the p38 MAPK signaling pathway with SB203580, respectively blocks MPO-mediated upregulation of ETRB protein expression. This has further advocate for the cell activating properties of MPO in the vessel wall, which is preceded by the avidity of MPO-binding to vascular compartments. Unlike endothelial cells, smooth muscle Metabolism Compound Library express both ET-1 receptors, the constitutive ETRA and the inducible ETRB. We indeed observed that MPO increased ETRB protein expression in smooth muscle cells, whereas ETRA expression remained unchanged. The functional consequence of MPO-driven ETRB expression was revealed using rat femoral arteries, which we exposed to the ETRB-specific agonist Sarafotoxin 6c (S6c) using the model of induced expression of ETRB by organ culture mimicking in vivo endothelial dysfunction [34], [35]. MPO further increased organ culture-induced ETRB-dependent vasoconstriction of rat vessels. The MPO-mediated ETRB expression on smooth muscle cells suggests to critically account for the additional increase in S6c-dependent vasoconstriction we observed.
Conclusion
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Introduction The intervertebral disc (IVD) is a key functional structure required for spinal movement [1]. Physiological aging and pathologic damage often lead to loss of physiological function of the IVD, resulting in degenerative disease [2]. Moreover, lifestyle changes, an aging society, and a range of environmental factors are leading to a gradual increase in the incidence of IVD degeneration [3]. Degenerative disc disease can cause chronic lower back pain, which is a common condition that can lead to an inability to work and even disability, and thus produces significant morbidity [4], [5]. The IVD relies on the diffusion of basal solutes through the cartilage end plate (CEP) for metabolic exchange and nutrient diffusion [6]. Cartilage end plate degeneration is a key factor in the development and progression of degenerative disc disease [7], [8]. The CEP attaches the inner ring of the IVD to the adjacent vertebral bodies and is an unusual tissue that comprises only a single cell type, cartilaginous end plate cells (CECs) [9]. CECs are chondrocyte-like cells important for the maintenance of the extracellular matrix (ECM) and subject to regulation by a wide variety of stimuli in normal and pathophysiological states, which can result in the uncontrolled turnover of the ECM [10], [11]. The ECM of the CEP expresses cartilage-specific genes, including collagen II and aggrecan. Loss of ECM is associated with reduced protein synthesis by CECs and degeneration of the CEP [12]. During the process of degeneration, cartilage-specific gene expression is suppressed by the downregulation of SOX9, a transcription factor associated with the expression of collagen II and aggrecan [13].