Racial differences in tumor necrosis factor-α-induced endothelial microparticles and interleukin-6 production

Abstract

African Americans (AA) tend to have heightened systemic inflammation and endothelial dysfunction. Endothelial microparticles (EMP) are released from activated/apoptotic endothelial cells (EC) when stimulated by inflammation. The purpose of our study was to assess EMP responses to inflammatory cytokine (TNF-α) and antioxidant (superoxide dismutase, SOD) conditions in human umbilical vein ECs (HUVECs) obtained from AA and Caucasians. EMPs were measured under four conditions: control (basal), TNF-α, SOD, and TNF-α + SOD. Culture supernatant was collected for EMP analysis by flow cytometry and IL-6 assay by ELISA. IL-6 protein expression was assessed by Western blot. AA HUVECs had greater EMP levels under the TNF-α condition compared to the Caucasian HUVECs (6.8 ± 1.1 vs 4.7% ± 0.4%, P = 0.04). The EMP level increased by 89% from basal levels in the AA HUVECs under the TNF-α condition (P = 0.01) compared to an 8% increase in the Caucasian HUVECs (P = 0.70). Compared to the EMP level under the TNF-α condition, the EMP level in the AA HUVECs was lower under the SOD only condition (2.9% ± 0.3%, P = 0.005) and under the TNF-α + SOD condition (2.1% ± 0.4%, P = 0.001). Basal IL-6 concentrations were 56.1 ± 8.8 pg/mL/μg in the AA and 30.9 ± 14.9 pg/mL/μg in the Caucasian HUVECs (P = 0.17), while basal IL-6 protein expression was significantly greater (P < 0.05) in the AA HUVECs. These preliminary observational results suggest that AA HUVECs may be more susceptible to the injurious effects of the proinflammatory cytokine, TNF-α.

Shear stress-induced mitochondrial biogenesis decreases the release of microparticles from endothelial cells

“…We previously demonstrated that MP release from ECs was increased in response to TNF-␣ and was attenuated with superoxide dismutase (6). Therefore, the level of EMP may reflect the inflammatory and oxidative stress of the ECs in vitro and in vivo as proposed recently (8).…”

“…Level of EMP production was determined by flow cytometry, as previously described (6). Briefly, samples were thawed at room temperature and centrifuged at 1,500 g for 20 min at room temperature to obtain platelet poor plasma.…”

Effect of Interleukin-10 and Laminar Shear Stress on Endothelial Nitric Oxide Synthase and Nitric Oxide in African American Human Umbilical Vein Endothelial Cells

“…[7][8][9][10] It has been well-documented in the literature that oxidative stress and inflammation often occur simultaneously and have been linked to endothelial dysfunction and hypertension. [29][30][31] Elucidating the mechanisms relating to inflammation, endothelial dysfunction, and hypertension may be beneficial in developing preventive measures in reducing the CVD risk burden among the African American population.…”

“…We have previously reported that African American endothelial cells had significantly greater levels of IL-6 protein expression and produced greater amounts of IL-6 in response to TNF-α, an inflammatory cytokine. 8 In addition, it was demonstrated that, compared with Caucasian endothelial cells, African American endothelial cells had significantly greater protein expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, the principal source of reactive oxygen species in endothelial cells. 9 The findings from our studies suggest a heightened inflammatory and oxidative stress status in African American endothelial cells.…”

“…5,6 The high incidence of hypertension in African Americans may be attributed to their predisposition to heightened systemic inflammation. [7][8][9][10] Long-term exposure of the endothelium to proinflammatory cytokines leads to endothelial dysfunction, which supports an environment favoring hypertension. 11,12 It is hypothesized that the intravascular balance between pro-and anti-inflammation plays a crucial role as a determinant of endothelial health.…”