Monocyte and Alveolar Macrophage Skewing Is Associated with the Development of Pulmonary Arterial Hypertension in a Primate Model of HIV Infection

Abstract

We investigated the relationship of monocytes, alveolar, and tissue-resident macrophage populations and the development of pulmonary arterial hypertension (PAH) in a nonhuman primate model of HIV infection. A prospective study of simian immunodeficiency virus-associated pulmonary arterial hypertension (SIV-PAH) was done. Rhesus macaques (n = 21) were infected with SIV. Blood, bronchoalveolar lavage fluid (BALF), and lung tissue were analyzed for monocyte and macrophage phenotypes and inflammatory mediators. Serial right heart catheterizations were performed at three time points throughout the study to assess hemodynamic alterations and the development of PAH. All 21 animals showed similar courses of SIV infection with an increasing proinflammatory plasma environment. At 6 months postinfection (mpi), 11 of 21 animals developed SIV-PAH (mPAP ≤25 mmHg; right ventricular systolic pressure [RVSP] ≤36 mmHg). PAH+ animals had an increased frequency of proinflammatory, nonclassical monocytes (CD14dimCD16+) (p = .06) in the peripheral blood and CD14+CCR7-CD163-CD206+ macrophages (p = .04) in BALF compared with PAH- animals at 6 mpi. Increased frequencies of these monocyte and macrophage phenotypes correlated with elevated RVSP (p = .04; p = .03). In addition, PAH+ animals had greater frequencies of tissue resident inflammatory M1-like CD68+STAT1+ (p = .001) and M2a-like CD68+STAT3+ macrophages (p = .003) and a lower frequency of anti-inflammatory M2c-like CD68+STAT6+ macrophages (p = .003) as well as fewer interleukin (IL)-10+ cells (p = .01). The results suggest that HIV-PAH is associated with skewing of monocytes and alveolar macrophages toward a proinflammatory, profibrotic phenotype. Furthermore, PAH+ animals may have diminished capacity to downregulate exaggerated chronic inflammation, as indicated by lower levels of IL-10 in PAH+ animals, contributing to disease progression.

Keywords: HIV-PAH; alveolar macrophage; monocyte; nonhuman primate.

FIG. 1.

SIV-infection induces a proinflammatory plasma and BALF environment. Monocyte and macrophage-associated cytokines and chemokines were quantified in (A) plasma and (B) BALF. While (A1) MCP-1/CCL2 and (A2) MDC/CCL22 only increased in plasma in chronic SIV-infection, levels of IP-10/CXCL10 increased in both plasma (A3) and BALF (B4). RANTES/CCL5 (B1), MIP-1β/CCL4 (B2), and MIG/CXCL9 (B3) significantly increased in BALF, but not in plasma. Full cytokine/chemokine analyses of this cohort are reported elsewhere. BALF, bronchoalveolar lavage fluid; SIV, Simian immunodeficiency virus.

FIG. 2.

Increased frequency of nonclassical monocytes correlates with elevated RVSP in SIV-PAH. (A1–3) Total monocyte counts, determined by a blood differential, did not change throughout SIV-infection and were not associated with PAH. (B) Nonclassical monocyte (CD14dimCD16+) counts and (C) classical monocyte (CD14+CD16−) counts were calculated based on the blood differential. (B1) Nonclassical monocytes levels did not change over time. (B2) At 6 mpi PAH+ animals had increased nonclassical monocyte counts over PAH−, which (B3) correlated with elevated RVSP. (C1) Classical monocytes levels increased at 6 mpi, but they were not associated with PAH (C2–3). PAH, pulmonary arterial hypertension; RVSP, right ventricular systolic pressure.

FIG. 3.

Alterations in BALF macrophage populations correlate with elevated RVSP in SIV-PAH. (A1) The frequency of macrophages in BALF decreased in chronic SIV-infection. At 6 mpi, (A2) PAH+ animals had a higher frequency of macrophages, which was linked to elevated RVSP (A3). CD14+CCR7+CD163−CD206− macrophages increased in chronic SIV-infection (B1), but were not associated with PAH (B2–3). CD14+CCR7−CD163−CD206+ cells increased at 6 mpi (C1). At 6 mpi, this macrophage phenotype was significantly increased in PAH+ animals (C2) and correlated with elevated RVSP (C3). The frequency of CD14+CCR7−CD163+CD206− macrophages did not change throughout SIV-infection (D1) and was not associated with PAH (D2–3). CD, cluster of differentiation; IL, interleukin; STAT, signal transducer and activator of transcription.

FIG. 4.

IHC evaluation of lung tissue. In addition to alveolar macrophages in BALF, tissue resident macrophages were characterized by the expression of CD68 and (A) STAT1, (B) STAT3, and (C) STAT6 and IHC. Additional H&E staining was performed for all tissue sections (A2, B2, C2). PAH+ animals have a higher frequency of CD68+STAT1+ (A3) and CD68+STAT3+ (B3) cells and a lower frequency of CD68+STAT6+ (C3) and IL-10+ cells (D3). H&E, hematoxylin and eosin; IHC, immunohistochemistry. Color images available online at www.liebertpub.com/aid