Circulating Microparticles Are Differentially Increased in Lowlanders and Highlanders with High Altitude Induced Pulmonary Hypertension during the Cold Season

Abstract

The role of microparticles (MPs) and cold in high altitude pulmonary hypertension (HAPH) remains unexplored. We investigated the impact of long-term cold exposure on the pulmonary circulation in lowlanders and high-altitude natives and the role of MPs. Pulmonary hemodynamics were evaluated using Doppler echocardiography at the end of the colder and warmer seasons. We further examined the miRNA content of MPs isolated from the study participants and studied their effects on human pulmonary artery smooth muscle (hPASMCs) and endothelial cells (hPAECs). Long-term exposure to cold environment was associated with an enhanced pulmonary artery pressure in highlanders. Plasma levels of CD62E-positive and CD68-positive MPs increased in response to cold in lowlanders and HAPH highlanders. The miRNA-210 expression contained in MPs differentially changed in response to cold in lowlanders and highlanders. MPs isolated from lowlanders and highlanders increased proliferation and reduced apoptosis of hPASMCs. Further, MPs isolated from warm-exposed HAPH highlanders and cold-exposed highlanders exerted the most pronounced effects on VEGF expression in hPAECs. We demonstrated that prolonged exposure to cold is associated with elevated pulmonary artery pressures, which are most pronounced in high-altitude residents. Further, the numbers of circulating MPs are differentially increased in lowlanders and HAPH highlanders during the colder season.

Keywords: chronic cold exposure; echocardiography; high altitude; microparticles; pulmonary hypertension.

Figure 1

High altitude location in Kyrgyzstan and experimental design. The photographs from high altitude village Sary-Mogol (approx. 3000 m) during the late summer (a) warmer season and late winter (b) colder season are presented. The photographs may have been previously posted on different social media and used for the documentary film. The experimental design is depicted (c). LA—lowlanders, HA—highlanders, C—control, P—pulmonary hypertension, MPs—microparticles.

Figure 2

Effects of the long-term exposure to cold on pulmonary circulation in Kyrgyz lowlanders (LA) and highlanders (HA). TRG—tricuspid regurgitant systolic pressure gradient (in mmHg). Results are presented as mean ± SEM (n = 63–87). * p < 0.05 values are considered statistically significant.

Figure 3

Effects of high altitude and cold on the circulating levels of different cells-derived microparticles (MPs) in Kyrgyz highlanders. (a–c) Flow cytometry characterization and quantification of different endothelial (CD62E) and inflammatory (T-cells (CD3) and macrophages (CD68)) cell-derived MPs are presented. LA—lowlanders, HA—highlanders, HAPH—highlanders with pulmonary hypertension. Results are presented as mean ± SEM (n = 10–12). * p < 0.05 values are considered statistically significant.

Figure 4

Effects of isolated microparticles (MPs) on proliferation and apoptosis of human pulmonary artery smooth muscle cells (PASMCs). Human PASMCs are exposed to isolated MPs and their effects on proliferation (a) and apoptosis (b) are shown. LA—lowlanders, HA—highlanders, HAPH—highlanders with pulmonary hypertension. Results are presented as mean ± SEM (n = 5–7). * p < 0.05 values are considered statistically significant.

Figure 5

Effects of high altitude and cold on the content of different micro RNAs (miRNAs) in isolated microparticles (MPs). The characterization and quantification of different miRNAs in isolated MPs are performed by PCR and presented (a–d). LA—lowlanders, HA—highlanders, HAPH—highlanders with pulmonary hypertension. Results are presented as mean ± SEM (n = 11–12). * p < 0.05 values are considered statistically significant.

Figure 6

Effects of isolated microparticles (MPs) on human pulmonary artery endothelial cells (PAECs): angiogenesis. Human PAECs are exposed to isolated MPs and their effects on different parameters of angiogenesis (a–c) are presented. LA—lowlanders, HA—highlanders, HAPH—highlanders with pulmonary hypertension. Results are presented as mean ± SEM (n = 3).

Figure 7

Effects of isolated microparticles (MPs) on human pulmonary artery endothelial cells (PAECs): expression profiles of vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS). Human PAECs are exposed to isolated MPs and their effects on expression profiles of VEGF (a) and eNOS (b) are analyzed by Western Blot and presented. LA—lowlanders, HA—highlanders, HAPH—highlanders with pulmonary hypertension. Results are presented as mean ± SEM (n = 4). * p < 0.05 values are considered statistically significant.