Increased plasma levels of extracellular mitochondrial DNA during HIV infection: A new role for mitochondrial damage-associated molecular patterns during inflammation
Introduction
The advent of combined antiretroviral therapy has deeply modified the prognosis of patients with human immunodeficiency virus type-1 (HIV-1) infection, but their life expectancy is still shorter than that of uninfected persons (Antiretroviral Therapy Cohort Collaboration, 2008). Several factors could account for this phenomenon, but the most recent data indicate that the vast majority of complications could be sustained, at least in part, by a chronic inflammatory state (Volberding and Deeks, 2010). This could be triggered and/or maintained by residual viral replication, persistent viral expression, loss of immunoregulatory cells that should dampen immune activation, increased fibrosis of lymph nodes, and microbial translocation (Deeks, 2009, Kuller et al., 2008).
Mitochondria are the main intracellular source of energy, in form of ATP, but can also produce dangerous molecules such as reactive oxygen species. Moreover, when cells are coping with an insult that is potentially harmful for the cell or for whole organism, they can release into the cytoplasm molecules that are able to trigger cell death such as cytochrome c or apoptosis inducing factor (Green and Kroemer, 2004).
Mitochondria contain several copies of a circular genome, the mitochondrial DNA (mtDNA), akin to a prokaryotic plasmid, codifying key proteins of the oxidative phosphorylation system, whose degradation origin formyl peptides. Recently, it has been shown that either mtDNA or degraded mitochondrial peptides can be involved in the pathogenesis of the systemic inflammatory response syndrome (SIRS), a condition that often affects patients who survive a trauma, and is characterized by the presence of shock and compromised function of several organs (Zhang et al., 2010). SIRS closely resembles sepsis, and is due, at least partially, to molecules called “damage-associated molecular patterns” (DAMPs). This novel, expanding family includes hyaluronan fragments, heat shock proteins, S100 proteins, amyloid-β, uric acid, interleukin (IL)-1α, IL-33, and the DNA-binding nuclear protein “high mobility group box 1” (Sims et al., 2010). DAMPs are conceptually similar to a set of conserved molecules defined “pathogen-associated molecular patterns” (PAMPs), which are produced and released by several microorganisms. PAMPs trigger a potent innate immune response, causing inflammation through the engagement of several Toll-like receptors (TLR), which can also be bound by DAMPs.
During trauma, mitochondrial DAMPs (MTDs) are released by damaged tissues, and found in high amounts in patients' plasma (Zhang et al., 2010). MTDs are represented by formyl peptides, that bind the formyl peptide receptor-1 (FPR-1), and mtDNA, that binds TLR-9, an intracellular receptor present in the endosomial system that responds to bacterial DNA, viral DNA and synthetic oligodeoxynucleotides containing unmethylated CpG motifs, like mtDNA. Injecting in rats MTDs equivalent to 5% of the liver causes a marked inflammation, with accumulation of albumin and elastase in lungs, influx of inflammatory cells in the airways and appearance of tumor necrosis factor (TNF)-α followed by IL-6 (Zhang et al., 2010).
It has been hypothesized that cells that are damaged during several pathological conditions such as chronic inflammations, ischemia–reperfusion injuries, or different infections can release mitochondrial structures (in particular: mtDNA, N-formyl peptides, cardiolipin, cytochrome c, ATP, carbamoyl phosphate synthetase-1, and finally reactive oxygen species) that trigger inflammation (Krysko et al., 2011, Manfredi and Rovere-Querini, 2010). As HIV-1 infection is characterized by a persistent chronic inflammation, we wondered whether MTDs could play a role in triggering or sustaining this phenomenon. For this purpose, we have studied plasma levels of mtDNA in HIV-1 positive patients showing a different course of the infection, and have correlated such levels to the activation of the immune system and to the plasma viremia. We analyzed individuals during acute primary infection (Cossarizza et al., 1995), patients with an advanced infection (including those with full blown acquired immunodeficiency syndrome, AIDS) but still naïve for antiretroviral therapy, and those defined “long term non progressors” (LTNPs), who had been infected since at least 8 years, always out of treatment, but with a normal number of CD4+ T cells, a low grade of apoptosis (Franceschi et al., 1997) and a good immunological control of the virus.
Section snippets
Study subjects
For this study, 37 HIV-1 positive patients, followed by the Infectious Disease Clinics of the Azienda Ospedaliero-Universitaria Policlinico di Modena, were enrolled. Informed consent was obtained from each patient before blood collection, according to the Italian laws.
Thirteen subjects had experienced a primary, acute HIV infection (AHI) and had not received any antiviral treatment (Cossarizza et al., 1997). The presumed date of infection was calculated as 1 month before undetermined western
Results and discussion
As shown in Fig. 1 (upper panel), we found that in all HIV-1 positive patients but LTNP plasma levels of mtDNA were significantly higher than in healthy controls. Furthermore, in patients naïve for antiretroviral therapy, 6 months of efficient HAART (able to increase CD4+ T cell count, decrease viral load and reduce T cell activation) did not modify mtDNA plasma levels (Fig. 1, lower panel). It is to note that in this paper we express the amount of extracellular mtDNA as copies per mL of plasma.
Fundings
This work was partially supported by grants from MIUR — PRIN 2008 to AC.
References (46)
- et al.
HIV infection and the gastrointestinal immune system
Mucosal Immunol.
(2008) - et al.
Quality assessment of human mitochondrial DNA quantification: MITONAUTS, an international multicentre survey
Mitochondrion
(2011) - et al.
Human immunodeficiency virus controllers: mechanisms of durable virus control in the absence of antiretroviral therapy
Immunity
(2007) - et al.
Mitochondrial membrane potential and nucleosidic inhibitors of HIV reverse transcriptase: a cytometric approach
Mitochondrion
(2004) - et al.
Protective effect of acetyl-l-carnitine against oxidative stress induced by antiretroviral drugs
FEBS Lett.
(2006) - et al.
Inflammaging and anti-inflammaging: a systemic perspective on aging and longevity emerged from studies in humans
Mech. Ageing Dev.
(2007) - et al.
Emerging role of damage-associated molecular patterns derived from mitochondria in inflammation
Trends Immunol.
(2011) - et al.
Functional characterization of the promoter of the human Lon protease gene
Mitochondrion
(2011) - et al.
Effects of chloroquine on viral infections: an old drug against today's diseases?
Lancet Infect. Dis.
(2003) - et al.
Antiretroviral therapy and management of HIV infection
Lancet
(2010)
Chloroquine enhances human CD8+ T cell responses against soluble antigens in vivo
J. Exp. Med.
Microbial translocation is associated with increased monocyte activation and dementia in AIDS patients
PLoS One
Life expectancy of individuals on combination antiretroviral therapy in high-income countries: a collaborative analysis of 14 cohort studies
Lancet
Development of TLR inhibitors for the treatment of autoimmune diseases
Immunol. Rev.
Quantitative analysis of circulating mitochondrial DNA in plasma
Clin. Chem.
Mitochondria alterations and dramatic tendency to apoptosis in peripheral blood lymphocytes during acute HIV syndrome
AIDS
Lack of selective Vβ deletion in CD4+ or CD8+ lymphocytes during acute HIV syndrome
AIDS
Mitochondrial functionality and mitochondrial DNA content in lymphocytes of vertically-infected HIV+ children with HAART-related lipodystrophy
J. Infect. Dis.
Increased mitochondrial DNA content in peripheral blood lymphocytes from HIV-infected patients with lipodystrophy
Antiviral Ther.
Immune dysfunction, inflammation, and accelerated aging in patients on antiretroviral therapy
Top. HIV Med.
Biomolecular screening of formyl peptide receptor ligands with a sensitive, quantitative, high-throughput flow cytometry platform
Nat. Protoc.
Direct analysis of mitochondrial toxicity of antiretroviral drugs
AIDS
Phenotypic characteristics and tendency to apoptosis of peripheral blood mononuclear cells from HIV+ long term non progressors
Cell Death Differ.
Cited by (79)
Roles of mitochondrial DNA in dynamics of the immune response to COVID-19
2022, GeneCitation Excerpt :Innate immune responses are triggered by mtDAMPs which are released from damaged or dying cells into the circulation of the host (Elesela and Lukacs 2021; Khan et al. 2015; West et al. 2011). Several potent immunological activators can induce the secretion of various proinflammatory cytokines causing cytokine storm (Hauser and Otterbein 2018; Itagaki et al. 2021) and increased plasma levels of extracellular mtDNA during various viral infection, such as HIV and HPV (Cossarizza et al. 2011; Feng et al. 2016). The release of mtDNA into the cytoplasm and out into the extracellular milieu induces different pattern recognition receptors and innate immune responses (Riley and Tait 2020).
Mitochondrial damage-associated molecular patterns stimulate reactive oxygen species production in human microglia
2020, Molecular and Cellular NeuroscienceCitation Excerpt :For some neurodegenerative disorders, such as PD and AD, disease-specific factors able to activate microglia have been discovered, whereas for others, such as MS, this research is still at its dawn. Considering therefore, the increasing relevance acquired by DAMPs in neurodegenerative diseases including MS (Bajwa et al., 2019; Leurs et al., 2018; Lowes et al., 2019; Nasi et al., 2019; Wilkins et al., 2015), our focus was to understand the role of microglia in eliciting sterile inflammation in various scenarios featured by low-grade, chronic forms of inflammation (Cossarizza et al., 2011; Pinti et al., 2012; Pinti et al., 2014). In particular, we investigated the effects of three different MTDs, i.e. DAMPs of mt origin: mtDNA, N-formyl peptides and CL.
Increased plasma levels of mitochondrial DNA and pro-inflammatory cytokines in patients with progressive multiple sclerosis
2020, Journal of NeuroimmunologySelf-DNA Sensing Fuels HIV-1-Associated Inflammation
2019, Trends in Molecular MedicineCitation Excerpt :The extracellular mtDNA content of blood plasma of HIV-1-infected participants of the Canadian Cellular Aging and HIV Comorbidities in Women and Children (CARMA) cohort was 46% higher than that of HIV-1 negative controls, and mtDNA content was positively correlated with nDNA content and with inflammation markers such as IL-6, in a multivariate model adjusted for IL-6, white blood cell content, and age [75]. Furthermore, in two cohorts studied in Modena (Italy) and Guangzhou (China), the plasma mtDNA content of treatment naïve HIV-1-infected patients was three times higher than that of healthy donors [76,77]. Of note, elevated levels of HMGB1 are frequently reported from the cerebrospinal fluid of patients with HIV-1-associated neurological disorders [78].
The Diagnostic, Prognostic, and Therapeutic Potential of Cell-Free DNA with a Special Focus on COVID-19 and Other Viral Infections
2023, International Journal of Molecular Sciences