Immune regulatory abnormalities produced by procainamide

Pulmonary gas exchange in the morbidly obese

The literature on pulmonary gas exchange at rest, during exercise, and with weight loss in the morbidly obese (body mass index or BMI > or = 40 kg m(-2)) is reviewed. Forty-one studies were found (768 subjects weighted mean = 40 years old, BMI = 48 kg m(-2)). The alveolar-to-arterial oxygen partial pressure difference (AaDO2) was large at rest in upright subjects at sea level (23, range 5-38 mmHg) while the arterial pressure of oxygen (PaO2) was low (81, range 50-95 mmHg). Arterial pressure of carbon dioxide (PaCO2) was normal. At peak exercise (162 W), gas exchange improves. Weight loss of 45 kg (BMI = -13 kg m(-2)) over 18 months is associated with an improvement in PaO2 (by 10 mmHg, range 1-23 mmHg), a reduction in AaDO2 (by 8 mmHg, range -3 to -16 mmHg), and PaCO2 (by -3 mmHg, range 3 to -14 mmHg) at rest. Every 5-6 kg reduction in weight increases PaO2 by 1 and reduces AaDO2 by 1 mmHg, respectively. Morbidly obese women have better gas exchange at rest compared with morbidly obese men which is likely due to lower waist-to-hip ratios in women than from differences in weight or BMI.

Obstructive Sleep Apnea and its Relationship to Cardiac Arrhythmias

Obstructive sleep apnea (OSA) affects approximately 4% of middle-aged men and 2% of middle-aged women. Cardiac arrhythmias are common problems in patients with OSA, even though the true prevalence and clinical relevance of cardiac arrhythmias remains to be determined. The presence and complexity of both tachyarrhythmias and bradyarrhythmias may influence morbidity, mortality, and the quality of life for OSA patients. Although the exact mechanisms underlying the link between OSA and cardiac arrhythmias are not well established, they could be partially the same proposed mechanisms relating OSA to different cardiovascular diseases. OSA is characterized by repetitive pharyngeal collapse during sleep that leads to markedly reduced or absent airflow, followed by oxyhemoglobin desaturation, persistent inspiratory efforts against an occluded airway, and termination by arousal from sleep. These mechanisms elicit a variety of autonomic, hemodynamic, humoral, and neuroendocrine responses that by themselves evoke acute and chronic changes in cardiovascular function. These effects may lead to the development of cardiac arrhythmias and any other form of cardiovascular disease linked to OSA. The aims of this review are to describe the essential cardiovascular pathophysiological aspects of OSA, to outline the relationship between OSA and both tachyarrhythmias and bradyarrhythmias and their possible influence in the natural history of OSA patients, and to assess the effects of OSA treatment on the presence of cardiac arrhythmias.

Clinical significance of sleep-related breathing disorders in patients with implantable cardioverter defibrillators

The prevalence and clinical significance of sleep-related breathing disorders (SRBDs) in patients with cardiac disease and a history of life-threatening ventricular tachyarrhythmias is unclear. Forty consecutive recipients of implantable cardioverter defibrillators (ICDs) with cardiac disease and a documented history of spontaneous, life-threatening, ventricular tachyarrhythmias underwent full night polysomnography. SRBDs were diagnosed if the apnea/hypopnea index was > 10. SRBD were diagnosed in 16 of 40 patients (40%): central sleep apnea (CSA) was present in 9 of these 16 patients (56%), 8 of whom had associated Cheyne-Stoke respiration. Seven of the 16 patients with SRBD (44%) had obstructive sleep apnea (OSA). Patients with and without SRBDs were comparable with respect to left ventricular ejection fraction, NYHA classification, underlying heart disease, ICD indications, and concomitant antiarrhythmic drug and beta-blocker therapy. Patients were followed prospectively for 2 years. ICD-treated ventricular tachyarrhythmias occurred in 10 of 24 patients (42%) without SRBD, in 4 of 9 patients (44%) with CSA, and in 3 of 7 patients (44%) with OSA (NS). The numbers and circadian distributions of episodes recorded during follow-up in patients without SRBD versus with CSA or OSA were not significantly different (14 +/- 25, median = 4 vs 4 +/- 5, median = 2.5 vs 15 +/- 15, median = 7, respectively). The 2-year mortality, which was entirely attributable to nonsudden cardiac events, was highest in patients with CSA (4/9 [44%], vs 0/7 [0%] with OSA, vs 3/24 patients (12.5%) without SRBD; P < 0.05).

Fluid intake and urinary incontinence in older community-dwelling women

Urinary incontinence (UI) is a common problem and requires adjustment to self-care. Noninvasive methods to manage UI should be tried first. Although many individuals restrict fluid intake to reduce incontinent episodes, clinical hunches suggest that adequate hydration is more useful in the management of UI. This study was conducted to determine the effects of hydration on the number of UI episodes. Women were randomly assigned to 1 of 3 groups: increase fluid intake by 500 cc, maintain fluid intake at baseline level, or decrease by 300 cc. Thirty-two women kept fluid intake and output diaries for 5 weeks. Adherence to fluid intake protocols was poor, and consequently, quantitative results were nonsignificant. However, follow-up interviews revealed that 20 women reported decreased UI episodes since participating in the study and felt that the most significant learning was their recognition of the need to increase fluid intake. Community health nurses can provide guidance in self-assessment of fluid intake patterns to help manage UI.

The effect of methyldopa and procainamide on suppressor cell activity in relation to red cell autoantibody production

Kirtland et al (1980) suggested that methyldopa caused the production of red cell (RBC) autoantibodies by causing a persistent increase in lymphocyte cyclic AMP, which inhibited suppressor T cell function, leading to unregulated autoantibody production in some patients. They showed that significantly higher lymphocyte cyclic AMP concentrations were generated by lymphocytes from healthy donors after adding methyldopa, and by lymphocytes from patients who were receiving methyldopa compared to lymphocytes from healthy donors without methyldopa present. They also showed that methyldopa affected suppressor cell activity. We measured the effect of methyldopa and procainamide on suppressor cell activity, using a similar approach to Kirtland et al (1980). Suppressor cell activity was measured by measuring the amount of IgG, produced in vitro, by B cells following mitogen stimulation preceded by a 24 h incubation period. We found no significant increase in the amount of IgG generated by normal donor lymphocytes, when methyldopa or procainamide was present during the preincubation period. This is in contrast to the findings of Kirtland et al (1980). We also measured the amount of IgG generated in vitro by mitogen-stimulated lymphocytes from patients (with and without positive direct antiglobulin tests) taking methyldopa and compared this to the amount of IgG generated by lymphocytes from normal donors and patients (with and without positive direct antiglobulin tests). The results were similar for each group. This does not agree with the findings of Kirtland et al (1980) who found that lymphocytes from patients taking methyldopa produced more IgG in vitro than lymphocytes from normal donors. Our results do not support the hypothesis that methyldopa and procainamide induce autoantibodies by affecting suppressor cell function.

Case Report: Distinctive Immune Abnormalities in a Patient with Procainamide-Induced Lupus and Serositis

To gain insight into the immunopathogenesis of drug-induced autoimmune disorders, lymphocyte and immunoglobulin distributions and cytokine levels were monitored in the peripheral blood and pleural fluid of a patient with procainamide-induced lupus and pleural effusion. Approximately 80% of the B cells in both compartments were CD5+ compared to 10% to 25% in normal adults. CD4/CD8 ratio and percentage CD4 were normal in peripheral blood. Serum levels of IgG (particularly IgG2), IL-6, and soluble IL-2R were slightly elevated, and those of IgA were significantly elevated compared to normal controls. Analysis of the pleural effusion revealed an increased CD4/CD8 ratio because of an increased percentage of CD4+CD29+ helper memory T cells, lack of expression of the resting B-cell marker CD21, immune complex deposition and complement consumption, increased relative levels of ANA, abnormally high levels of IL-6 and soluble IL-2R, and detectable levels of IL-1b, IFN-g and TNF-a. These observations provide evidence for the involvement of CD5+ B cells and differential helper T-cell activity in procainamide-induced lupus and for an association between local lymphocyte activation and organ pathology.

The role of leukocyte-generated reactive metabolites in the pathogenesis of idiosyncratic drug reactions

Evidence strongly suggests that many adverse drug reactions, including idiosyncratic drug reactions, involve reactive metabolites. Furthermore, certain functional groups, which are readily oxidized to reactive metabolites, are associated with a high incidence of adverse reactions. Most drugs can probably form reactive metabolites, but a simple comparison of covalent binding in vitro is unlikely to provide an accurate indication of the relative risk of a drug causing an idiosyncratic reaction because it does not provide an indication of how efficiently the metabolite is detoxified in vivo. In addition, the incidence and nature of adverse reactions associated with a given drug is probably determined in large measure by the location of reactive metabolite formation, as well as the chemical reactivity of the reactive metabolite. Such factors will determine which macromolecules the metabolites will bind to, and it is known that covalent binding to some proteins, such as those in the leukocyte membrane, is much more likely to lead to an immune-mediated reaction or other type of toxicity. Some reactive metabolites, such as acyl glucuronides, circulate freely and could lead to adverse reactions in almost any organ; however, most reactive metabolites have a short biological half-life, and although small amounts may escape the organ where they are formed, these metabolites are unlikely to reach sufficient concentrations to cause toxicity in other organs. Many idiosyncratic drug reactions involve leukocytes, especially agranulocytosis and drug-induced lupus. We and others have demonstrated that drugs can be metabolized by activated neutrophils and monocytes to reactive metabolites. The major reaction appears to be reaction with leukocyte-generated hypochlorous acid. Hypochlorous acid is quite reactive, and therefore it is likely that many other drugs will be found that are metabolized by activated leukocytes. Some neutrophil precursors contain myeloperoxidase and the NADPH oxidase system, and it is likely that these cells can also oxidize drugs. Therefore, although there is no direct evidence, it is reasonable to speculate that reactive metabolites generated by activated leukocytes, or neutrophil precursors in the bone marrow, could be responsible for drug-induced agranulocytosis and aplastic anemia. This could involve direct toxicity or an immune-mediated reaction. These mechanisms are not mutually exclusive, and it may be that both mechanisms contribute to the toxicity, even in the same patient. In the case of drug-induced lupus, a prevalent hypothesis for lupus involves modification of class II MHC antigens.(ABSTRACT TRUNCATED AT 400 WORDS)

Respiratory variability and associated cardiovascular changes in adults at rest

Breathing patterns and associated circulatory fluctuations may reflect the action of various regulatory mechanisms as well as mechanical influences of breathing on the circulation. Thus, the study of such patterns can enhance our knowledge of these mechanisms, both in normal and pathological conditions. In this review, literature is evaluated that provides insight into the breath-to-breath variation of respiration in quietly breathing adults. Also when respiration is seemingly random, deterministic patterns in the respiratory variability can often be discerned. The various methods used in the recognition of such patterns and their possible interpretation are discussed. Furthermore, the question is addressed how respiratory variability can affect the circulation and how this can be studied by analysing the time relationships of respiratory and circulatory parameters. This may add to both the understanding of normal cardiovascular regulation and to insight into cardiovascular disturbances under unstable respiratory conditions. As examples of such circumstances, some common conditions are discussed that are often, though not always, associated with pathology, viz. Cheyne-Stokes respiration, snoring and the sleep apnoea syndrome.

Metabolism of procainamide to the cytotoxic hydroxylamine by neutrophils activated in vitro

An almost universal side effect of long-term therapy with procainamide is the appearance of serum autoantibodies and less frequently a syndrome resembling lupus erythematosus. Previous studies demonstrated that procainamide-hydroxylamine (PAHA), a metabolite generated by hepatic mixed function oxidases, was highly toxic to dividing cells, but evidence that PAHA could be formed in the circulation was lacking. This study examines the capacity of neutrophils to metabolize procainamide to reactive forms. Neutrophils activated with opsonized zymosan were cytotoxic only if procainamide was present, whereas N-acetyl procainamide, which does not induce autoimmunity, was inert in this bioassay. PAHA was detected by HPLC in the extracellular medium if ascorbic acid was present. Generation of PAHA and cytotoxic procainamide metabolites was inhibited by NaN3 and catalase but not by superoxide dismutase, indicating that H2O2 and myeloperoxidase were involved. Nonactivated neutrophils and neutrophils from patients with chronic granulomatous disease did not generate cytotoxic PAHA, demonstrating that H2O2 was derived from the respiratory burst accompanying neutrophil activation. These conclusions were supported by results of a cell-free system in which neutrophils were replaced by myeloperoxidase and H2O2 or an H2O2 generating system. These studies demonstrate the capacity of neutrophils to mediate metabolism of procainamide and establish the role of myeloperoxidase released during degranulation and H2O2 derived from the respiratory burst in the direct cooxidation of procainamide to PAHA. The profound biologic activity of this metabolite and its possible generation within lymphoid compartments implicate this process in the induction of autoimmunity by procainamide.

Procainamide induces a transitory impairment of B cell mitogenesis in beagle dogs

Beagle dogs (3 to 6 years old) were treated with 100-150 mg procainamide HC1/kg/day. After 2, 5, and 9 months of treatment, peripheral blood lymphocytes were isolated and stimulated with pokeweed mitogen. The data demonstrated a suppression of mitogenesis only at 2 and 5 months after procainamide treatment. The lymphocytes from dogs treated for 9 months had a normal response to pokeweed mitogen. At no time during this experiment were any significant levels of serum antinuclear antibodies detected nor was any change in the number of cycling lymphocytes apparent in the experimental versus control groups. The resting membrane potential of both control and experimental groups was similar and pokeweed mitogen depolarized the cells from both groups.

Autoimmunity induced by chemicals

Immunotoxicologic studies have demonstrated that autoimmune responses and/or autoimmune diseases are induced in humans and experimental animals by chronic exposure to various chemicals. The present review is focused on seven groups of chemically induced human disorders, i.e. systemic lupus erythematosus, autoimmune hemolytic anemia, myasthenia gravis, pemphigus, glomerulonephritis, thyroiditis and hepatitis. Results obtained from studies of the available experimental counterparts of these diseases, i.e. those models obtained from the exposure of laboratory animals to various chemicals, are then analyzed. Finally, we present the lessons that can be derived from immunotoxicologic investigations regarding mechanisms of induction, heterogeneity of chemicals involved, humoral vs. cellular immune responses and genetic predisposition to chemically induced autoimmunity.

Increased presence of common systemic lupus erythematosus (SLE) anti-DNA idiotypes (16/6 Id, 32/15 Id) is induced by procainamide

Sixty-seven patients on treatment with procainamide were examined for the presence of two common idiotypes of anti-DNA antibodies (16/6 Id and 32/15 Id). These idiotypes have been shown previously to have clinical relevance in patients with systemic lupus erythematosus (SLE). An enzyme-linked immunosorbent assay (ELISA) with rabbit anti-Id antibodies revealed increased concentrations of the 16/6 Id and 32/15 Id in 25 (37%) and 16 (24%) patients, respectively. Five of eight patients with drug-induced lupus had elevated titers of both idiotypes. A high correlation (R = 0.56, P less than 0.001 for 16/6 Id) was found between Id levels and anti-single-stranded DNA (ssDNA) antibody titers and between 16/6 Id titers and antihistone antibodies (IgG, R = 0.43; IgM, R = 0.25). It seems that procainamide, a component known to be associated with drug-induced lupus, may induce an increased production of common anti-DNA idiotypes in apparently normal subjects.

Antibodies in procainamide-induced and systemic lupus erythematosus bind the C-terminus of histone 1 (H1)

The sera of patients with systemic lupus erythematosus (SLE) and drug-induced lupus (DIL) were used to study the antigenic regions of histone 1 (H1) that bind antibodies in these sera. ELISA and immunoblotting techniques using enzymatically and chemically derived peptides of H1 showed that the major antigenic domain is in the carboxyl (C) terminus. None of the 24 SLE or 11 DIL sera bound to the central hydrophobic polypeptide by ELISA. The reactivity of DIL sera with the purified H1 peptides was similar to that observed with SLE sera. This observation suggests a common immune pathway for DIL and SLE.

The origin of autoantibodies

Autoimmune diseases are characterized by the appearance of autoantibodies (autoAb) which may participate in their pathogenesis, but autoAb have also been found in normals with a variety of other conditions. The production of hybridomas from lymphocytes of unimmunized normal mice and healthy humans and analysis of the monoclonal autoAb (m-autoAb) obtained, showed that many had polyspecific autoAb reactivity, binding to many seemingly unrelated self-antigens, or to several organs. Most m-autoAb were of the IgM class and shared a common cross-reactive idiotype (CRI). Low levels of Ab with similar binding pattern and idiotype are continuously represented in the serum of mice and humans who have no evidence of autoimmune or other disease. Very similar Ab appear in autoimmune diseases. Studies of m-autoAb derived from lupus-prone mice and from patients with systemic lupus erythematosus (SLE) and other autoimmune diseases also revealed polyspecific binding, IgM isotype and CRI. Moreover, these CRI, which were almost identical with the idiotypes of natural autoAb in normals, may identify a group of pathogenic Ab in the lupus mice and SLE patients. Since the data clearly suggest that lymphocytes that make autoAb are common and are part of the normal B cell repertoire coded by widely dispersed germline genes, there remain the basic problems of the function of these autoAb in health, as well as the question of their regulation and activation in vivo. Several postulated functions and immunoregulatory mechanisms are discussed and the possible role of certain factors, especially viruses, in enhancing autoAb production and autoimmunity, is assessed.

Recognition of major histocompatibility complex antigens on murine glial cells

Recognition of autologous major histocompatibility complex (MHC) antigens by T cells is an essential step in the induction of an immunologic reaction to either endogenous or exogenous antigens. We investigated the ability of murine glial cells of different ages to stimulate clones of allospecific T lymphocytes. We also investigated the effects of supernatants from cultures of activated T cells on the immunologic recognition of MHC antigens on murine glial cells. Lymphocyte clones specific for Class I, Class II and non-MHC, background antigens were obtained from C57B1/6J-anti-DBA/2 mixed lymphocyte cultures. Glial cell cultures were prepared from newborn syngeneic (C57B1/6J) and allogeneic (DBA/2) mouse brains. Glial cultures 1-4 weeks of age were able to stimulate alpha-Class I-specific clones. No stimulation of alpha-Class II or alpha-background clones was noted. Incubation of glial cells with supernatants from cultures of alloantigen-activated spleen cells (C57B1/6J-anti-DBA/2) resulted in a decreased ability of glial cells to stimulate alpha-Class I responses. In contrast supernatant-treated cultures acquired the capacity to stimulate alpha-Class II-specific clones. No responses were noted in clones responsive to non-MHC antigens. The ability to stimulate alpha-Class II-specific clones was most prominent with one-week-old glial cultures and was lost by four weeks of culture. The increased susceptibility of younger glial cultures to the modulatory effects of lymphokines from activated T cells may be a factor in the increased susceptibility of the immature central nervous system to persistent viral infections and the development of autoimmune phenomena.

In vivo self-reactivity of mononuclear cells to T cells and macrophages exposed to HgCl2

Mercuric chloride induces in Brown-Norway rats a polyclonal activation of B cells resulting in a lymphoproliferation and in the production of autoantibodies. Experiments were performed to test the role of cells modified by HgCl2 in the induction of B cell proliferation by using the popliteal lymph node assay. Spleen cells, T cells and peritoneal macrophages exposed in vivo or in vitro to HgCl2 induced a proliferation of T and B cells in the draining popliteal lymph node. Spleen cells from Lewis rats who received HgCl2 were ineffective. These data suggest that modified cells could trigger autologous lymphocyte subsets and be responsible for autoimmunity induced by HgCl2.

Effects of long-term procainamide therapy on immunoglobulin synthesis

Procainamide is a potent inducer of autoantibodies. In order to evaluate the immunologic effects of this drug in vivo, 23 cardiac disease patients who had received procainamide for at least 6 months and an equal number of matched cardiac disease control subjects were studied, and percentage of circulating T cell subsets, concanavalin A-induced suppressor cell activity, and pokeweed mitogen--stimulated generation of immunoglobulin-secreting cells was quantitated. There was no significant difference between patient and control groups in the percentage of T cell subsets defined by OKT4 and OKT8 monoclonal antibodies or in concanavalin A-induced suppressor cell activity. The numbers of pokeweed mitogen--induced immunoglobulin-secreting cells were markedly decreased in the patient group, as measured by the protein A-augmented reverse hemolytic plaque assay (3,000 +/- 644, mean +/- SEM in patients versus 10,826 +/- 1,529, mean +/- SEM in control subjects, P less than 0.005). Removal of the adherent cell fraction did not improve the hyporesponsiveness. When B and T cell fractions of 6 patients were mixed with normal T and B cell fractions, all of the patients demonstrated diminished B cell responses, and one-half also had diminished T cell responses. Addition of patient adherent cells to a co-culture of normal B cells with deficient patient T cells restored plaque formation to normal levels, suggesting that the T cell defect was correctable by a macrophage-derived factor. The data obtained suggest that procainamide exerts an immuno-suppressive action on both B and T cell function in patients receiving this drug.

Captopril and immune regulation

We examined the in vitro effect of captopril (2.5 to 5 micrograms/ml) on the primary antibody response of human B cells. Captopril suppresses (by 50%) the specific anti-trinitrophenyl (TNP) response of unfractionated peripheral blood mononuclear cells (PBM) but not that of nonadherent PBM. The susceptibility to captopril suppression can be restored in the latter cell cultures by 10% adherent radioresistant cells. This suppression is independent of prostaglandins. In transfer experiments, cells preincubated with 5 micrograms/ml captopril suppress the antibody response of autologous nonadherent PBM. The inductive phase of this suppression requires both adherent cells and radiosensitive T cells. Once induced, the suppression can be transferred by isolated T effector cells. In vivo after a unique oral intake of captopril a moderate suppressor activity can be demonstrated in adherent cells from normal individuals. We conclude that captopril interferes with the immune regulation by inducing a suppressor circuit involving monocytes and a T8 suppressor effector lymphocyte.