Disrupted endothelial cell heterogeneity and network organization impair vascular function in prediabetic obesity

Abstract

Background: Obesity is a major risk factor for diabetes and cardiovascular diseases such as hypertension, heart failure, and stroke. Impaired endothelial function occurs in the earliest stages of obesity and underlies vascular alterations that give rise to cardiovascular disease. However, the mechanisms that link weight gain to endothelial dysfunction are ill-defined. Increasing evidence suggests that endothelial cells are not a population of uniform cells but are highly heterogeneous and are organized as a communicating multicellular network that controls vascular function. Purpose: To investigate the hypothesis that disrupted endothelial heterogeneity and network-level organization contribute to impaired vascular reactivity in obesity. Methods and results: To study obesity-related vascular function without complications associated with diabetes, a state of prediabetic obesity was induced in rats. Small artery diameter recordings confirmed nitric-oxide mediated vasodilator responses were dependent on increases in endothelial calcium levels and were impaired in obese animals. Single-photon imaging revealed a linear relationship between blood vessel relaxation and population-wide calcium responses. Obesity did not alter the slope of this relationship, but impaired calcium responses in the endothelial cell network. The network comprised structural and functional components. The structural architecture, a hexagonal lattice network of connected cells, was unchanged in obesity. The functional network contained sub-populations of clustered specialized agonist-sensing cells from which signals were communicated through the network. In obesity there were fewer but larger clusters of sensory cells and communication path lengths between clusters increased. Communication between neighboring cells was unaltered in obesity. Altered network organization resulted in impaired, population-level calcium signaling and deficient endothelial control of vascular tone. Conclusions: The distribution of cells in the endothelial network is critical in determining overall vascular response. Altered cell heterogeneity and arrangement in obesity decreases endothelial function and provides a novel framework for understanding compromised endothelial function in cardiovascular disease.

Mitochondrial ATP production is required for endothelial cell control of vascular tone

“…We next asked, how does mitochondrial ATP facilitate nitric oxide-mediated vasodilation? The Ach-nitric oxide vasodilator pathway is mediated via muscarinic (M3 subtype [33]), Gαq-dependent stimulation of phospholipase C and the subsequent hydrolysis of phosphatidylinositol-4,5-bisphosphate (PIP2) to produce IP 3 , Once liberated, IP 3 activates IP 3 receptors evoke, in turn, Ca 2+ release from internal stores, Ca 2+ influx via store-operated Ca 2+ entry, and Ca 2+ -dependent activation of endothelial nitric oxide synthase [28,30]. Because functional mitochondria are required for basal (unstimulated) endothelial cell Ca 2+ signaling [34], we speculated that mitochondrial ATP synthase control of nitric-oxide mediated vasodilator signaling (Figures 1–3) arises via the nucleotide’s control of IP 3 -mediated Ca 2+ signaling.…”

A new model for regulation of sphingosine kinase 1 translocation to the plasma membrane in breast cancer cells

“…Intracellular Ca 2+ was monitored using the Ca 2+ -sensitive fluorescent indicator, Cal-520 ( 36 , 37 ). For this, MCF-7L breast cancer cells were plated in ibidi μ-Slide 8-well culture dishes and left to adhere for 24 h (37 °C, 5% CO 2 ).…”

“…Temporal Ca 2+ signals were extracted from the raw fluorescence intensity image stacks, using 30-pixel (∼4 μm) diameter circular regions of interest manually positioned at the center of each cell. Ca 2+ signals were analyzed using a custom Python-based analysis suite as described previously ( 36 , 37 ). The average initial Ca 2+ peak response evoked by carbachol in the absence and presence of YM254890 was analyzed in GraphPad Prism, v7.01 (GraphPad).…”

The Mechanisms of the Development of Atherosclerosis in Prediabetes

“…Obesity changes the network activity and decreases the cell populations that respond to acetylcholine, causing vasodilation, increasing sensory cell clusters, and lengthening the distance for information transmission between cell clusters. For example, Wilson et al demonstrated that communication between endothelial cells is disrupted in rats with prediabetic obesity [ 50 ]. They found that obesity impaired the calcium response in the endothelial cell network, leading to insufficient endothelial vascular tone control.…”