Autoantibodies to lipids in bronchoalveolar lavage fluid of patients with acute respiratory distress syndrome

IgG immune complex-induced acute lung injury is ameliorated by cAMP via down-regulation of C/EBP- and AP-1-mediated transcriptions

BACKGROUND

Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS) are life threatening pulmonary diseases, and we are now lack of effective therapeutic methods. Inflammatory responses are essential for initiating ALI/ARDS. Thus, ameliorating inflammatory reaction might be beneficial for treatment of the disease. There are increasing data that phosphodiesterase-4 (PDE4)-selective inhibitors, which may elevate cellular cyclic adenosine 3', 5'-monophosphate (cAMP) level, could suppress inflammation. However, whether they could be used to treat IgG immune complex (IgG-IC)-associated ALI has not been determined.

METHODS

ALI is induced by treating mice with airway deposition of IgG immune complexes. Cellular cAMP concentrations are elevated by treating mice or macrophages with Rolipram/Roflumilast. The degree of pulmonary injury is reflected by lung permeability, leukocyte accumulation, histological change and expressions of pro-inflammatory mediators. 6-Bnz-cAMP and H-89 are used to regulate protein kinase A (PKA) activity, and 8-pCPT-2'-O-Me-cAMP is applied to activate exchange proteins directly activated by cAMP (Epac). Gene expressions are analyzed by real-time PCR, ELISA or Western blot. CCAAT/enhancer binding protein (C/EBP) and activation protein 1 (AP-1) transcription activities are estimated by measuring the luciferase productions.

RESULTS

IgG-IC-induced ALI is attenuated by the PDE4-selective inhibitor, which is due to reduced expressions of cytokine and chemokines. Interestingly, we find that cAMP downstream effector molecule PKA but not Epac is involved in negative regulation of IgG-IC-mediated pro-inflammatory mediators' productions. Mechanistically, activation of cAMP-PKA signal axis leads to inactivation of MAPK pathway, resulting in a decrease in C/EBP- and AP-1-mediated transcriptions of pro-inflammatory mediators.

CONCLUSIONS

Our data demonstrate, for the first time, that cAMP-PKA signal is involved in down-regulation of IgG-IC-associated inflammatory responses via down-regulating MAPK activation, which is critical for transcriptional activities of C/EBP and AP-1. Collectively, our experiments provide theoretical base for the potential application of PDE4-selective inhibitor to clinic for treatment of IgG-IC-related acute lung injury.

The pulmonary pathology of COVID-19

The lung is the main affected organ in severe coronavirus disease 2019 (COVID-19) caused by the novel coronavirus SARS-CoV-2, and lung damage is the leading cause of death in the vast majority of patients. Mainly based on results obtained by autopsies, the seminal features of fatal COVID-19 have been described by many groups worldwide. Early changes encompass edema, epithelial damage, and capillaritis/endothelialitis, frequently combined with microthrombosis. Subsequently, patients with manifest respiratory insufficiency exhibit exudative diffuse alveolar damage (DAD) with hyaline membrane formation and pneumocyte type 2 hyperplasia, variably complicated by superinfection, which may progress to organizing/fibrotic stage DAD. These features, however, are not specific for COVID-19 and can be found in other disorders including viral infections. Clinically, the early disease stage of severe COVID-19 is characterized by high viral load, lymphopenia, massive secretion of pro-inflammatory cytokines and hypercoagulability, documented by elevated D-dimers and an increased frequency of thrombotic and thromboembolic events, whereas virus loads and cytokine levels tend to decrease in late disease stages, when tissue repair including angiogenesis prevails. The present review describes the spectrum of lung pathology based on the current literature and the authors' personal experience derived from clinical autopsies, and tries to summarize our current understanding and open questions of the pathophysiology of severe pulmonary COVID-19.

Antiphospholipid Syndrome and the Lungs

Antiphospholipid syndrome (APS) is a systemic autoimmune disease characterised by recurrent thromboembolic events (arterial or venous) and/or morbidity in pregnancy (fetal loss, premature birth, or recurrent embryonic losses) in the presence of laboratory evidence of antiphospholipid antibodies (aPL). APS is a multisystem disorder. Several lung manifestations may develop in patients with APS including pulmonary embolism (PE)/infarction; thromboembolic and non-thromboembolic pulmonary hypertension (PH) (pulmonary arterial hypertension); pulmonary microthrombosis; acute respiratory distress syndrome associated with catastrophic APS; diffuse alveolar haemorrhage; and pulmonary capillaritis. Postpartum syndrome and cryptogenic fibrosing alveolitis (CFA) can be associated with APS. Pulmonary manifestations are relatively rare but are more likely to be life-threatening compared with other complications of APS. Particularly in the presence of aPL, pulmonary manifestations should be suspected in any systemic lupus erythematosus patient with clinical findings such as chest pain, dyspnoea, tachypnoea, and haemoptysis. Early diagnosis and treatment of pulmonary manifestations in APS are essential for improving mortality rates in patients with this condition. The purpose of this review is to assess current evidence around the diagnosis, prognosis, and management of patients with common and rare pulmonary manifestations of APS.

Antiphospholipid antibodies in critically ill patients

Antiphospholipid antibodies are responsible for a wide spectrum of clinical manifestations. Venous, arterial and microvascular thrombosis and severe catastrophic cases account for a large morbidly/mortality. Through the connection between the immune, inflammatory and hemostatic systems, it is possible that these antibodies may contribute to the development of organ dysfunction and are associated with poor short and long-term prognoses in critically ill patients. We performed a search of the PubMed/MedLine database for articles written during the period from January 2000 to February 2013 to evaluate the frequency of antiphospholipid antibodies in critically ill patients and their impact on the outcomes of these patients. Only eight original studies involving critically ill patients were found. However, the development of antiphospholipid antibodies in critically ill patients seems to be frequent, but more studies are necessary to clarify their pathogenic role and implications for clinical practice.

Does activation of the FcgammaRIIa play a role in the pathogenesis of the acute lung injury/acute respiratory distress syndrome?

ALI (acute lung injury) and its more severe form ARDS (acute respiratory distress syndrome) are inflammatory diseases of the lung characterized by hypoxaemia and diffuse bilateral infiltrates. Disruption of epithelial integrity and injury to endothelium are contributing factors of the development of ALI/ARDS, and alveolar damage is the most pronounced feature of ALI/ARDS. The resulting increase in lung microvascular permeability promotes influx of inflammatory cells to the alveolar spaces. Oedema fluid contains pro-nflammatory mediators and plasma proteins, including Igs (immunoglobulins). Moreover, several reports describe the presence of autoantibodies and immune complexes [anti-IL-8 (interleukin-8) autoantibody/IL-8 complexes] in lung fluids (oedema and bronchoalveolar lavage fluids) from patients with ALI/ARDS. These immune complexes associate with FcgammaRIIa (Fcgamma IIa receptor) in lungs of patients with ARDS. Furthermore, the expression of FcgammaRIIa is substantially elevated in lungs of these patients. FcgammaRIIa appears on virtually all myeloid cells, platelets and endothelial cells. It is a low-affinity receptor for IgG that preferentially binds aggregated immunoglobulins and immune complexes. FcgammaRs regulate phagocytosis and cell-mediated cytotoxicity, and initiate the release of inflammatory mediators. It should be noted that immune complexes formed between either anti-neutrophil autoantibodies and their specific antigens or anti-HLA (human leucocyte antigen) antibodies and target antigens are implicated in the pathogenesis of TRALI (transfusion-related acute lung injury), and importantly, animal studies indicate that FcgammaRs are essential for these complexes to cause damage to the lungs. Therefore, we hypothesize that FcgammaRs such as FcgammaRIIa could contribute to the pathogenesis of ALI/ARDS.

Anti-IL-8 autoantibody:IL-8 immune complexes suppress spontaneous apoptosis of neutrophils

Our previous studies demonstrated that a significant fraction of interleukin-8 (IL-8) in lung fluids from patients with acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) is associated with anti-IL-8 autoantibodies (anti-IL-8:IL-8 immune complexes). Neutrophils have been implicated in the pathogenesis of ALI/ARDS, and moreover, it is well-established that apoptosis of neutrophils is delayed in patients with ALI/ARDS. The aim of this study was, therefore, to examine the role of anti-IL-8:IL-8 immune complexes in modulating spontaneous apoptosis of normal human neutrophils. Apoptosis was assessed by evaluating morphological changes, measuring enzymatic activity of caspase-3, and determining the extent of DNA degradation. We found that samples containing anti-IL-8:IL-8 immune complexes but not samples from which these complexes were removed inhibited neutrophil apoptosis. Furthermore, the former samples or effectively anti-IL-8:IL-8 complexes induced an increase in the level of antiapoptotic protein, Bcl-X(L). In contrast, levels of proapoptotic proteins Bax and Bak were decreased in the same conditions. Activity of both caspase-3 and caspase-9 was also suppressed by anti-IL-8:IL-8 complex-containing samples. Finally, we established that IgG receptor, FcgammaRIIa, mediates antiapoptotic activity of anti-IL-8:IL-8 complexes and that the key components of the FcgammaRIIa signaling pathway, Src, Syk, PI3 kinase, and ERK, may be involved in regulation of neutrophil apoptosis by the complexes. These studies demonstrate for the first time that anti-IL-8:IL-8 immune complexes have the ability to prolong neutrophil life.

Catastrophic antiphospholipid syndrome presented with severe hypertension, adult respiratory distress syndrome and unilateral adrenal haemorrhagic infarction

We are reporting a case of catastrophic antiphospholipid syndrome (CAPS) in an adult female manifested with severe hypertension followed by adrenal haemorrhagic infarction and adult respiratory distress syndrome. Adrenal involvement appears to be exceedingly high in CAPS and adult respiratory distress syndrome (ARDS) is the prevailing pulmonary manifestation in this condition, compared with these impediments in patients with simple antiphospholipid syndrome (APS). Even though the above manifestations are well recognized, their combination as an initial presentation of CAPS is uncommon.

Identification of immunoglobulins that recognize 3-nitrotyrosine in patients with acute lung injury after major trauma

Tyrosine nitration is a nitric oxide-derived post-translational modification of proteins. Elevated levels of specific plasma proteins modified by tyrosine nitration have been detected during acute and chronic inflammatory conditions, including acute lung injury (ALI). In the present study we examined whether circulating immunoglobulins against nitrated proteins are present in the plasma of subjects with clinically documented ALI. Affinity chromatography using covalently linked 3-nitrotyrosine was employed to identify plasma proteins that bind to this unusual amino acid. Western blotting and liquid chromatography-tandem mass spectrometry of in-gel digested protein bands revealed that the major proteins eluted from the affinity column were IgM and IgG. An enzyme-linked immunosorbent assay (ELISA) based on competition of horseradish peroxidase-derivatized 3-nitrotyrosine binding to plasma with unlabeled 3-nitrotyrosine was developed and validated. Using this ELISA, the levels of immunoglobulins that recognize 3-nitrotyrosine were significantly higher in the plasma of subjects with ALI compared with both normal control subjects and subjects with major trauma who did not develop ALI (0.36+/- 0.14 versus 0.03 +/- 0.05, and 0.25 +/- 0.15; P < 0.001 and P = 0.006, respectively). These data indicate that tyrosine-nitrated proteins induce the production of specific immunoglobulins during acute phase response and inflammation.

The acute respiratory distress syndrome in catastrophic antiphospholipid syndrome: analysis of a series of 47 patients

BACKGROUND

The acute respiratory distress syndrome (ARDS) is a non-cardiogenic form of pulmonary oedema characterised by severe hypoxaemia refractory to oxygen therapy, with diffuse pulmonary infiltrates on chest radiographs. It can be precipitated by various serious medical and surgical conditions, including systemic autoimmune diseases. The "catastrophic" variant of the antiphospholipid syndrome (APS) is an accelerated form of this systemic autoimmune condition which results in multiorgan failure because of multiple small vessel occlusions.

OBJECTIVE

To analyse the clinical and laboratory characteristics of patients with catastrophic APS who develop ARDS.

METHODS

Cases with ARDS were selected from the web site based international registry of patients with catastrophic APS (CAPS registry) (http://www.med.ub.es/MIMMUN/FORUM/CAPS.HTM) and their characteristics examined.

RESULTS

Pulmonary involvement was reported in 150 of 220 patients with catastrophic APS (68%) and 47 patients (21%) were diagnosed as having ARDS. Nineteen (40%) of these patients died. Pathological studies were undertaken in 10 patients and thrombotic microangiopathy was present in seven. There were no differences in age, sex, precipitating factors, clinical manifestations, or mortality between catastrophic APS patients with and without ARDS.

CONCLUSIONS

ARDS is the dominant pulmonary manifestation of catastrophic APS. Thus the existence of ARDS in the context of an APS makes it necessary to rule out the presence of the catastrophic variant of this syndrome.

Anti-phospholipid antibodies in serum from patients with Guillain-Barré syndrome

OBJECTIVE

The Guillain-Barré syndrome (GBS) is an acute inflammatory polyneuropathy related to autoimmunity. However, no conclusive etiological concept has yet been found. We examined the variation in autoantibodies to lipids in serum of GBS patients in response to the course of the disease but investigated titer modifications during treatment with gamma-globulin.

DESIGN AND SETTING

Prospective clinical study in a 14-bed general ICU.

PATIENTS

Nine patients with GBS and nine controls were included in the study.

MEASUREMENTS AND RESULTS

Four blood samples were obtained before and after treatment. Serum samples, diluted 1:60, were tested by enzyme-linked immunosorbent assay for IgM, IgA, and IgG antibodies to phosphatidylcholine, phosphatidylinositol, cardiolipin, phosphatidic acid, phosphatidylserine, phosphatidylglycerol, phosphatidylethanolamine, sphingomyelin, and gangliosides. Anti-phospholipid antibodies of the IgM, IgA, and IgG families were detected in all GBS patients but in none of the controls. Phosphatidylinositol, cardiolipin, phosphatidylcholine, and phosphatidic acid were the main antigens. All patients developed anti-phosphatidylinositol antibodies of the IgM family and anti-cardiolipin antibodies of the IgA and IgG families. A decrease in the level of anti-phospholipid autoantibodies was observed after 1 day of treatment with gamma-globulin. Two days after ending gamma-globulin administration the IgG antibodies increased again.

CONCLUSIONS

Our findings suggest that in GBS there is an extensive immune reaction, which is altered after gamma-globulin treatment. Anti-cardiolipin and anti-phosphatidylinositol antibodies could be useful markers for the response to treatment.

Prospective observational study of antiphospholipid antibodies in acute lung injury and acute respiratory distress syndrome: comparison with catastrophic antiphospholipid syndrome

Detection of antiphospholipid (aPL) antibodies in bronchoalveolar lavage fluid (BALF) of patient with acute respiratory distress syndrome (ARDS) suggests involvement of autoimmune mechanisms in the pathogenesis of ARDS. We investigated whether aPL antibodies could be detected in the serum as well as BALF of patients with acute lung injury (ALI) and ARDS. IgG anticardiolipin, IgG anti-beta2-glycoprotein I, IgG antiphosphatidic acid and IgG antiphosphatidylserine antibodies were detected by ELISA in low titers within the normal range in the BALF and serum of nine patients with ALI and 17 patients with ARDS. However, one out of 27 patients investigated had high levels of aPL antibodies in both BALF and serum. This patient suffered from severe ARDS due to sepsis. The high aPL antibody levels in serum possibly triggered by sepsis were associated with high aPL antibody levels in BALF, which can be explained by high capillary-alveolar permeability. Computed tomography scan revealed widespread infarctions in brain, spleen and kidneys, and pulmonary thromboembolism, suggesting the diagnosis of catastrophic antiphospholipid syndrome.

Lipids are co-eluted with immunoglobulins G during purification by recombinant streptococcal protein G affinity chromatography

The efficiency of recombinant streptococcal protein G (rec-spG) affinity column chromatography in purifying immunoglobulins G (IgG) from lipids has been studied, with particular reference to IgG fractions from bronchoalveolar lavage (BAL) fluid and serum samples from different sources. It was found that the IgG fractions purified by rec-spG affinity column chromatography also contained cholesterol and phospholipids.