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editorial
. 2021 Mar 30;65(4):341–342. doi: 10.1165/rcmb.2021-0222ED

Extracellular Vesicles: Progress and Challenges in the Study of Human Immunodeficiency Virus and Cocaine-associated Pulmonary Arterial Hypertension

Camilla Margaroli 1, Derek Russell 2,3
PMCID: PMC8525209  PMID: 34166601

Pulmonary arterial hypertension (PAH) is a disease characterized by progressive remodeling of the pulmonary vasculature, resulting in higher vascular resistance and premature death. The incidence of Group I PAH is markedly elevated in patients with chronic infection with the human immunodeficiency virus (HIV) (1). A better understanding of PAH pathology has led to the approval of 14 therapies since the early 1990s (2), but mechanisms leading to increased incidence in a population with associated risk factors such as HIV remain poorly understood. Extracellular vesicles (EVs) have been shown to be elevated in patients with PAH and to contribute to the disease in animal models (3, 4), suggesting a significant role in regulating PAH development and progression.

In this issue of the Journal, Krishnamachary and colleagues (pp. 413–429) address the role of EVs in the pathophysiology of PAH in patients infected with HIV with concurrent cocaine abuse (5) (an important and common risk modifier for PAH in the HIV+ population) (6). In an elegant series of experiments, using clinical samples as well as in vitro and in vivo models, they define a role for plasma EVs in patients with HIV (especially in the presence of concurrent cocaine exposure) via increased EV expression of transforming growth factor-β1 (TGF-β1), a central mediator of PAH pathophysiology (7). The authors show that endothelial, smooth muscle cell, and right ventricular dysfunction associated with pulmonary vasculopathy are tied to the delivery of TGF-β1 via EVs, whose biogenesis they link, at least in part, to cells of the macrophage–monocyte lineage. There are many aspects of this pathway yet to be explained. However, the authors convincingly demonstrate that TGF-β1 signaling, which is thought to be fundamental to cardiopulmonary complications of HIV and cocaine abuse (as well as to PAH per se), can be mediated to a significant degree by EVs and that this pathway is itself modulated by cocaine exposure.

This science carries significance for future research. EVs, long treated as cellular “dust” or detritus (8), have gained increasing prominence as critical mediators of respiratory disease (9, 10), including roles in the pulmonary vasculopathy of both World Health Organization Group 1 (11) (to which HIV-associated PAH pertains) and Group 3 (10) forms of the disease. It seems likely that EVs are involved in a great number of key pathophysiological processes within PAH (including roles downstream of TGF-β signaling [12]) and elsewhere. However, EVs are technically and scientifically challenging to study, and the work of Krishnamachary and colleagues highlights not only the importance but also the complexity of such work. As such, a number of potentially confounding factors must be noted to contextualize these data. First, given the size and density of the virions, as well as the potential presence of self-proteins and lipids carried over through the budding process, one has to consider the presence of viral particles in the EV fraction isolated either by canonical methods such as ultracentrifugation, bead-based pulldown, or other methods (13). Because virion secretion coopts aspects of the exosome-secretion machinery (and corresponding “EV markers”), and because HIV virion secretion exists along a spectrum between complete, functional viruses and incomplete, EV-like particles that simply incorporate one or more viral elements (e.g., viral proteins and/or nucleic acids) (14), the distinction between EV and virus is not clearly demarcated. Indeed, it has been shown that EVs can carry viral proteins as well as the transactivation response element RNA from HIV itself (15, 16), elements which may themselves facilitate TGF-β1 signaling in smooth muscle cells (17). Also, no perfect EV purification method exists, and it is difficult to obtain pure, uncontaminated, and unselected populations of EVs, especially from complex biological fluids like plasma (13). Lastly, administration of cocaine can itself have a strong effect on the rate of EV production as well as the type of cargo that they deliver to target cells (18), adding another layer of complexity to the study of this system. By using the HIV-transgenic rat model, validating their principal findings across strata of viremia, varying EV purification techniques, and using complementary cell culture–based experiments, Krishnamachary and colleagues have attenuated, but not eliminated, some of these potential confounders. Their findings must be viewed with these caveats in mind, and future, more mechanistic interrogation of this system remains needed.

Nonetheless, this work adds to a growing body of research demonstrating that EVs carry powerful biological impact in human disease, and it adds important information on the pathogenesis of PAH in HIV and cocaine use. The outsized power of these nano-sized particles also suggests promise; some EVs may also have protective effects (19), and there may be potential to manipulate EVs for use as either therapeutic targets or delivery of therapeutic cargos (20, 21) in PAH and in other diseases.

In summary, there is much work yet to do before we realize the potential of EV research, but Krishnamachary and colleagues are to be applauded. Careful, well-designed, and intricate studies such as this are critical for advancing our knowledge of the complexities of PAH biology and EV signaling. This can be a challenging, even laborious, process. However, continued examination of these pathways fits Teddy Roosevelt’s famous maxim of “hard work worth doing,” as it sets the stage for potential preventative, monitoring, and treatment strategies that improve the health of patients.

Footnotes

Supported by the National Institutes of Health, National Heart, Lung, and Blood Institute grant 1 K08 HL148514-01 (D.R.) and the Cystic Fibrosis Foundation Research Development Program Grant ROWE19R0 (C.M.).

Originally Published in Press as DOI: 10.1165/rcmb.2021-0222ED on June 24, 2021

Author disclosures are available with the text of this article at www.atsjournals.org.

References

  • 1. Isasti G, Moreno T, Pérez I, Cabrera F, Palacios R, Santos J. High prevalence of pulmonary arterial hypertension in a cohort of asymptomatic HIV-infected patients. AIDS Res Hum Retroviruses. 2013;29:231–234. doi: 10.1089/AID.2012.0166. [DOI] [PubMed] [Google Scholar]
  • 2. Galie N, McLaughlin VV, Rubin LJ, Simonneau G. An overview of the 6th World Symposium on Pulmonary Hypertension. Eur Respir J. 2019;53:1802148. doi: 10.1183/13993003.02148-2018. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3. Aliotta JM, Pereira M, Amaral A, Sorokina A, Igbinoba Z, Hasslinger A, et al. Induction of pulmonary hypertensive changes by extracellular vesicles from monocrotaline-treated mice. Cardiovasc Res. 2013;100:354–362. doi: 10.1093/cvr/cvt184. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4. Amabile N, Heiss C, Real WM, Minasi P, McGlothlin D, Rame EJ, et al. Circulating endothelial microparticle levels predict hemodynamic severity of pulmonary hypertension. Am J Respir Crit Care Med. 2008;177:1268–1275. doi: 10.1164/rccm.200710-1458OC. [DOI] [PubMed] [Google Scholar]
  • 5. Krishnamachary B, Mahajan A, Kumar A, Agarwal S, Mohan A, Chen L, et al. Extracellular vesicle TGF-β1 is linked to cardiopulmonary dysfunction in human immunodeficiency virus. Am J Respir Cell Mol Biol. 2021 doi: 10.1165/rcmb.2021-0010OC. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 6. Dash S, Balasubramaniam M, Villalta F, Dash C, Pandhare J. Impact of cocaine abuse on HIV pathogenesis. Front Microbiol. 2015;6:1111. doi: 10.3389/fmicb.2015.01111. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 7. Rol N, Kurakula KB, Happé C, Bogaard HJ, Goumans MJ. TGF-β and BMPR2 signaling in PAH: two black sheep in one family. Int J Mol Sci. 2018;19:2585. doi: 10.3390/ijms19092585. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8. Hargett LA, Bauer NN. On the origin of microparticles: from “platelet dust” to mediators of intercellular communication. Pulm Circ. 2013;3:329–340. doi: 10.4103/2045-8932.114760. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9. Soni S, Garner JL, O’Dea KP, Koh M, Finney L, Tirlapur N, et al. Intra-alveolar neutrophil-derived microvesicles are associated with disease severity in COPD. Am J Physiol Lung Cell Mol Physiol. 2021;320:L73–L83. doi: 10.1152/ajplung.00099.2020. [DOI] [PubMed] [Google Scholar]
  • 10. Genschmer KR, Russell DW, Lal C, Szul T, Bratcher PE, Noerager BD, et al. Activated PMN exosomes: pathogenic entities causing matrix destruction and disease in the lung. Cell. 2019;176:113–126.e15. doi: 10.1016/j.cell.2018.12.002. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 11.Taylor S, Contrepois K, Benayoun BA, Jiang L, Isobe S, Wang L, et al. Endogenous retroviral elements generate pathologic neutrophils and elastase rich exosomes in pulmonary arterial hypertension [preprint] https://www.biorxiv.org/content/10.1101/2021.01.08.426001v1.full [DOI] [PMC free article] [PubMed]
  • 12. de la Cuesta F, Passalacqua I, Rodor J, Bhushan R, Denby L, Baker AH. Extracellular vesicle cross-talk between pulmonary artery smooth muscle cells and endothelium during excessive TGF-β signalling: implications for PAH vascular remodelling. Cell Commun Signal. 2019;17:143. doi: 10.1186/s12964-019-0449-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 13. Théry C, Witwer KW, Aikawa E, Alcaraz MJ, Anderson JD, Andriantsitohaina R, et al. Minimal information for studies of extracellular vesicles 2018 (MISEV2018): a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines. J Extracell Vesicles. 2018;7:1535750. doi: 10.1080/20013078.2018.1535750. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14. Nolte-’t Hoen E, Cremer T, Gallo RC, Margolis LB. Extracellular vesicles and viruses: are they close relatives? Proc Natl Acad Sci USA. 2016;113:9155–9161. doi: 10.1073/pnas.1605146113. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 15. Narayanan A, Iordanskiy S, Das R, Van Duyne R, Santos S, Jaworski E, et al. Exosomes derived from HIV-1-infected cells contain trans-activation response element RNA. J Biol Chem. 2013;288:20014–20033. doi: 10.1074/jbc.M112.438895. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 16. Patters BJ, Kumar S. The role of exosomal transport of viral agents in persistent HIV pathogenesis. Retrovirology. 2018;15:79. doi: 10.1186/s12977-018-0462-x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 17. Dalvi P, Sharma H, Konstantinova T, Sanderson M, Brien-Ladner AO, Dhillon NK. Hyperactive TGF-β signaling in smooth muscle cells exposed to HIV-protein(s) and cocaine: role in pulmonary vasculopathy. Sci Rep. 2017;7:10433. doi: 10.1038/s41598-017-10438-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 18. Kumar S, Crenshaw BJ, Williams SD, Bell CR, Matthews QL, Sims B. Cocaine-specific effects on exosome biogenesis in microglial cells. Neurochem Res. 2021;46:1006–1018. doi: 10.1007/s11064-021-03231-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 19. Lee C, Mitsialis SA, Aslam M, Vitali SH, Vergadi E, Konstantinou G, et al. Exosomes mediate the cytoprotective action of mesenchymal stromal cells on hypoxia-induced pulmonary hypertension. Circulation. 2012;126:2601–2611. doi: 10.1161/CIRCULATIONAHA.112.114173. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 20. Sindi HA, Russomanno G, Satta S, Abdul-Salam VB, Jo KB, Qazi-Chaudhry B, et al. Therapeutic potential of KLF2-induced exosomal microRNAs in pulmonary hypertension. Nat Commun. 2020;11:1185. doi: 10.1038/s41467-020-14966-x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 21. Ferrer E, Dunmore BJ, Hassan D, Ormiston ML, Moore S, Deighton J, et al. A potential role for exosomal translationally controlled tumor protein export in vascular remodeling in pulmonary arterial hypertension. Am J Respir Cell Mol Biol. 2018;59:467–478. doi: 10.1165/rcmb.2017-0129OC. [DOI] [PMC free article] [PubMed] [Google Scholar]

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