Rheumatol Int (2014) 34:341–345 DOI 10.1007/s00296-013-2889-7
SHORT COMMUNICATION
Smoking, disease activity, permanent damage and dsDNA autoantibody production in patients with systemic lupus erythematosus Susanne Ekblom‑Kullberg · Hannu Kautiainen · Pirkko Alha · Marjatta Leirisalo‑Repo · Aaro Miettinen · Heikki Julkunen
Received: 12 August 2013 / Accepted: 21 October 2013 / Published online: 30 October 2013 © Springer-Verlag Berlin Heidelberg 2013
Abstract The aim was to study the association of smoking with the activity and severity of systemic lupus erythematosus (SLE) and the production of antibodies to dsDNA. The study included 223 SLE patients attending the outpatient clinics at Helsinki University Central Hospital. The history of smoking was obtained by personal interview, and clinical data related to SLE by interview, clinical examination and chart review. The activity of SLE was assessed by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score and permanent damage by the SLICC/ACR score. Antibodies to dsDNA were determined by three ELISA assays, by the indirect immunofluorescence technique using Crithidia luciliae cells as substrates and by the Farr assay. There were no significant differences in the SLEDAI scores between current smokers (73 patients), ex-smokers (59) and never-smokers (91), though current smokers tended to have lower disease
activity. The SLICC/ACR scores between the groups were practically equal. Current smokers had significantly lower levels of antibodies to dsDNA than ex- and never-smokers (p = 0.025). Our study suggests that cigarette smoke may have immunosuppressive effect on autoantibody production in patients with SLE. Permanent damage was not found to be associated with smoking.
S. Ekblom‑Kullberg · M. Leirisalo‑Repo Department of Medicine, Institute of Clinical Medicine, University of Helsinki, P.O. Box 20, 00014 Helsinki, Finland
M. Leirisalo‑Repo Division of Rheumatology, Department of Medicine, Helsinki University Central Hospital (HUS), P.O. Box 372, 00029 Helsinki, Finland
Keywords Systemic lupus erythematosus · Smoking · Anti-dsDNA antibodies · Activity · Damage
Introduction Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disease with a highly variable clinical
S. Ekblom‑Kullberg (*) Finnish Red Cross Blood Service, Kivihaantie 7, 00310 Helsinki, Finland e-mail: susanne.ekblom‑[email protected]
A. Miettinen Haartman Institute, University of Helsinki, P.O. Box 21, 00014 Helsinki, Finland
H. Kautiainen Department of General Practice and Primary Health Care, Institute of Clinical Medicine, University of Helsinki, P.O. Box 20, 00014 Helsinki, Finland
A. Miettinen Department of Immunology, Laboratory Diagnostics, Helsinki University Central Hospital (HUS), P.O. Box 720, 00029 Helsinki, Finland
H. Kautiainen Department of General Practice, Primary Health Care Unit, Turku University Hospital, P.O. Box 52, 20521 Turku, Finland
H. Julkunen Division of Rheumatology, Department of Medicine, Helsinki University Central Hospital (HUS), Peijas Hospital, P.O. Box 900, 00029 Vantaa, Finland
P. Alha National Institute for Health and Welfare, P.O. Box 30, 00271 Helsinki, Finland
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course. SLE can be active for many years, periods of activity and inactivity can vary, or the disease can go into a longterm, even permanent, remission. The clinical picture and the activity and severity of SLE are influenced by intrinsic and extrinsic factors, including sex, genes, hormones, ultraviolet light, infectious agents, diet, drugs and many other yet unknown factors [1]. Cigarette smoke is one of the greatest sources of environmental exposures to toxic chemicals and is known to affect the development, course and outcome of many autoimmune diseases. In patients with SLE, smoking is reported to be a risk factor for the development of the disease and associated with specific clinical features such as end-stage renal disease [2, 3]. The association of smoking with the overall clinical activity of SLE has been controversial, as well the association with cumulative organ damage of the disease [3–5]. Anti-dsDNA antibodies serve as a marker for disease activity and prognosis, and it may have a role in the etiopathogenesis of SLE [6]. The cause of autoantibody production in SLE and in other autoimmune diseases is, however, unknown. One explanation may be that endogenous proteins are altered by exogenous factors and recognized as foreign antigens resulting in antibody production. Cigarette smoke contains toxic agents that can cause oxidative DNA damage and lead to genetic mutations [7]. Whether smoking is associated with the production of dsDNA antibodies in patients with SLE has been controversial. One study showed a significantly higher risk of dsDNA seropositivity in current smokers versus ex- and never-smokers [8], while another study reported a negative correlation of smoking with IgG anti-dsDNA antibodies in newly diagnosed SLE patients [9]. In this study, we sought to find out whether smoking is associated with the activity and severity of SLE and the production of antibodies to dsDNA.
Methods SLE patients and data collection Adult patients with a clinical diagnosis of SLE attending Helsinki University Central Hospital were informed about this study and, if they agreed to participate, were personally interviewed and clinically examined by two rheumatologists (SE-K and HJ). Hospital charts were reviewed. The study included 223 patients, all of whom fulfilled the criteria for SLE [10]. Based on earlier reported prevalence figures of SLE in our country (28/100,000) [11], we estimated that about 80–85 percent of all SLE patients requiring hospital-based treatment living in the area (about 1 million inhabitants) were included in the study.
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Rheumatol Int (2014) 34:341–345
A detailed history of the clinical manifestations was obtained from each patient, and the activity and severity of SLE were recorded by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI, original version) [12] and the accumulated organ damage index SLICC/ACR [13], respectively. Routine laboratory tests for the SLEDAI score were determined, and additional serum samples were stored at −20 °C. Questions related to smoking were as follows. Have you ever smoked? Have you smoked at least 100 times? Have you smoked daily for more than one year? How many years have you smoked daily? Do you smoke currently (daily, occasionally or not at all)? When did you last smoke? How many cigarettes (cigars or pipes of tobacco) do you smoke daily (or did before you stopped smoking)? The study was approved by the Ethics Committee at Helsinki University Central Hospital. Antibodies to dsDNA Anti-telomere IgG antibodies were determined using a specific ELISA test (Anti-dsDNA test kit Cat. No. AI 003 010, Biohit Plc, Helsinki, Finland) and anti-dsDNA antibodies to calf thymus dsDNA by ELISA using two assays (Immunocap™ anti-dsDNA and Farrzyme™ anti-dsDNA) according to the manufacturers’ instructions. In addition, anti-dsDNA antibodies were determined by the indirect immunofluorescence technique using Crithidia luciliae cells (NOVA Lite™ dsDNA, INOVA Diagnostics, Inc, San Diego, CA) as substrates and by the Farr assay using a commercial kit (Medix, Biochemica, Kauniainen, Finland). Statistical analysis The data are presented as means with standard deviations or as medians with interquartile range (IQR) or as counts with percentages. The 95 % CI are given for the most important outcomes. Statistical significance between groups was tested by Chi-square test, Kruskal–Wallis test and analysis of variance. In the case of violation of the assumptions (non-normality), a bootstrap-type test was used. The normality of the variables was tested using the Shapiro–Wilk W test. Correlations were estimated with Spearman’s rank correlation coefficient method.
Results Demographic characteristics of the patients Patients, who were daily smokers or had smoked at least 100 times during their lifetime, were classified as ever smokers (132 patients). Of these 132 patients, 59 had
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Rheumatol Int (2014) 34:341–345 Table 1 Demographic characteristics of the patients Ex-smokera N = 59
Current smoker N = 73 Female, n (%) Age, mean (SD) Body mass index, mean (SD) Age at diagnosis, mean (SD) Duration of SLE, median (IQR), years Education years, mean (SD) Total household income (1,000 €), median (IQR) Marital status, n (%) Married/living with a spouse Divorced/widowed/separated Never married Depression score, median (IQR)
Never-smoker N = 91
p value
63 (86)
53 (90)
89 (98)
0.021
44 (13) 23.6 (4.6) 32 (13) 10 (4, 20) 12.4 (3.2) 11 (9, 16)
49 (14) 25.3 (4.3) 37 (12) 11 (4, 19) 12.7 (3.1) 14 (9, 27)
47 (16) 23.7 (4.2) 34 (16) 12 (5, 20) 13.8 (3.4) 16 (9, 27)
0.12 0.044 0.13 0.57 0.013 0.034 0.011
29 (40) 19 (26) 25 (34)
36 (61) 9 (15) 14 (24)
61 (67) 12 (13) 18 (20)
5 (3, 11)
6 (2, 12)
5 (2, 8)
0.23
a
Stopped smoking for more than 6 months before the study
No significant differences were found in the SLEDAI (p = 0.20) or SLICC/ACR (p = 0.88) scores between current smokers, ex- and never-smokers (Fig. 1). Current smokers tended to have lower disease activity than ex- and never-smokers. The SLICC/ACR scores between the three groups were almost identical. Smoking, C3 and antibodies to dsDNA Current smokers had significantly lower levels of antibodies to dsDNA than ex- and never-smokers (p = 0.025, Fig. 2). The differences in the C3 levels between the groups were insignificant (p = 0.92). There was a good correlation between the anti-dsDNA results by all five assays, complement C3, and the SLEDAI score (p
SHORT COMMUNICATION
Smoking, disease activity, permanent damage and dsDNA autoantibody production in patients with systemic lupus erythematosus Susanne Ekblom‑Kullberg · Hannu Kautiainen · Pirkko Alha · Marjatta Leirisalo‑Repo · Aaro Miettinen · Heikki Julkunen
Received: 12 August 2013 / Accepted: 21 October 2013 / Published online: 30 October 2013 © Springer-Verlag Berlin Heidelberg 2013
Abstract The aim was to study the association of smoking with the activity and severity of systemic lupus erythematosus (SLE) and the production of antibodies to dsDNA. The study included 223 SLE patients attending the outpatient clinics at Helsinki University Central Hospital. The history of smoking was obtained by personal interview, and clinical data related to SLE by interview, clinical examination and chart review. The activity of SLE was assessed by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score and permanent damage by the SLICC/ACR score. Antibodies to dsDNA were determined by three ELISA assays, by the indirect immunofluorescence technique using Crithidia luciliae cells as substrates and by the Farr assay. There were no significant differences in the SLEDAI scores between current smokers (73 patients), ex-smokers (59) and never-smokers (91), though current smokers tended to have lower disease
activity. The SLICC/ACR scores between the groups were practically equal. Current smokers had significantly lower levels of antibodies to dsDNA than ex- and never-smokers (p = 0.025). Our study suggests that cigarette smoke may have immunosuppressive effect on autoantibody production in patients with SLE. Permanent damage was not found to be associated with smoking.
S. Ekblom‑Kullberg · M. Leirisalo‑Repo Department of Medicine, Institute of Clinical Medicine, University of Helsinki, P.O. Box 20, 00014 Helsinki, Finland
M. Leirisalo‑Repo Division of Rheumatology, Department of Medicine, Helsinki University Central Hospital (HUS), P.O. Box 372, 00029 Helsinki, Finland
Keywords Systemic lupus erythematosus · Smoking · Anti-dsDNA antibodies · Activity · Damage
Introduction Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disease with a highly variable clinical
S. Ekblom‑Kullberg (*) Finnish Red Cross Blood Service, Kivihaantie 7, 00310 Helsinki, Finland e-mail: susanne.ekblom‑[email protected]
A. Miettinen Haartman Institute, University of Helsinki, P.O. Box 21, 00014 Helsinki, Finland
H. Kautiainen Department of General Practice and Primary Health Care, Institute of Clinical Medicine, University of Helsinki, P.O. Box 20, 00014 Helsinki, Finland
A. Miettinen Department of Immunology, Laboratory Diagnostics, Helsinki University Central Hospital (HUS), P.O. Box 720, 00029 Helsinki, Finland
H. Kautiainen Department of General Practice, Primary Health Care Unit, Turku University Hospital, P.O. Box 52, 20521 Turku, Finland
H. Julkunen Division of Rheumatology, Department of Medicine, Helsinki University Central Hospital (HUS), Peijas Hospital, P.O. Box 900, 00029 Vantaa, Finland
P. Alha National Institute for Health and Welfare, P.O. Box 30, 00271 Helsinki, Finland
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342
course. SLE can be active for many years, periods of activity and inactivity can vary, or the disease can go into a longterm, even permanent, remission. The clinical picture and the activity and severity of SLE are influenced by intrinsic and extrinsic factors, including sex, genes, hormones, ultraviolet light, infectious agents, diet, drugs and many other yet unknown factors [1]. Cigarette smoke is one of the greatest sources of environmental exposures to toxic chemicals and is known to affect the development, course and outcome of many autoimmune diseases. In patients with SLE, smoking is reported to be a risk factor for the development of the disease and associated with specific clinical features such as end-stage renal disease [2, 3]. The association of smoking with the overall clinical activity of SLE has been controversial, as well the association with cumulative organ damage of the disease [3–5]. Anti-dsDNA antibodies serve as a marker for disease activity and prognosis, and it may have a role in the etiopathogenesis of SLE [6]. The cause of autoantibody production in SLE and in other autoimmune diseases is, however, unknown. One explanation may be that endogenous proteins are altered by exogenous factors and recognized as foreign antigens resulting in antibody production. Cigarette smoke contains toxic agents that can cause oxidative DNA damage and lead to genetic mutations [7]. Whether smoking is associated with the production of dsDNA antibodies in patients with SLE has been controversial. One study showed a significantly higher risk of dsDNA seropositivity in current smokers versus ex- and never-smokers [8], while another study reported a negative correlation of smoking with IgG anti-dsDNA antibodies in newly diagnosed SLE patients [9]. In this study, we sought to find out whether smoking is associated with the activity and severity of SLE and the production of antibodies to dsDNA.
Methods SLE patients and data collection Adult patients with a clinical diagnosis of SLE attending Helsinki University Central Hospital were informed about this study and, if they agreed to participate, were personally interviewed and clinically examined by two rheumatologists (SE-K and HJ). Hospital charts were reviewed. The study included 223 patients, all of whom fulfilled the criteria for SLE [10]. Based on earlier reported prevalence figures of SLE in our country (28/100,000) [11], we estimated that about 80–85 percent of all SLE patients requiring hospital-based treatment living in the area (about 1 million inhabitants) were included in the study.
13
Rheumatol Int (2014) 34:341–345
A detailed history of the clinical manifestations was obtained from each patient, and the activity and severity of SLE were recorded by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI, original version) [12] and the accumulated organ damage index SLICC/ACR [13], respectively. Routine laboratory tests for the SLEDAI score were determined, and additional serum samples were stored at −20 °C. Questions related to smoking were as follows. Have you ever smoked? Have you smoked at least 100 times? Have you smoked daily for more than one year? How many years have you smoked daily? Do you smoke currently (daily, occasionally or not at all)? When did you last smoke? How many cigarettes (cigars or pipes of tobacco) do you smoke daily (or did before you stopped smoking)? The study was approved by the Ethics Committee at Helsinki University Central Hospital. Antibodies to dsDNA Anti-telomere IgG antibodies were determined using a specific ELISA test (Anti-dsDNA test kit Cat. No. AI 003 010, Biohit Plc, Helsinki, Finland) and anti-dsDNA antibodies to calf thymus dsDNA by ELISA using two assays (Immunocap™ anti-dsDNA and Farrzyme™ anti-dsDNA) according to the manufacturers’ instructions. In addition, anti-dsDNA antibodies were determined by the indirect immunofluorescence technique using Crithidia luciliae cells (NOVA Lite™ dsDNA, INOVA Diagnostics, Inc, San Diego, CA) as substrates and by the Farr assay using a commercial kit (Medix, Biochemica, Kauniainen, Finland). Statistical analysis The data are presented as means with standard deviations or as medians with interquartile range (IQR) or as counts with percentages. The 95 % CI are given for the most important outcomes. Statistical significance between groups was tested by Chi-square test, Kruskal–Wallis test and analysis of variance. In the case of violation of the assumptions (non-normality), a bootstrap-type test was used. The normality of the variables was tested using the Shapiro–Wilk W test. Correlations were estimated with Spearman’s rank correlation coefficient method.
Results Demographic characteristics of the patients Patients, who were daily smokers or had smoked at least 100 times during their lifetime, were classified as ever smokers (132 patients). Of these 132 patients, 59 had
343
Rheumatol Int (2014) 34:341–345 Table 1 Demographic characteristics of the patients Ex-smokera N = 59
Current smoker N = 73 Female, n (%) Age, mean (SD) Body mass index, mean (SD) Age at diagnosis, mean (SD) Duration of SLE, median (IQR), years Education years, mean (SD) Total household income (1,000 €), median (IQR) Marital status, n (%) Married/living with a spouse Divorced/widowed/separated Never married Depression score, median (IQR)
Never-smoker N = 91
p value
63 (86)
53 (90)
89 (98)
0.021
44 (13) 23.6 (4.6) 32 (13) 10 (4, 20) 12.4 (3.2) 11 (9, 16)
49 (14) 25.3 (4.3) 37 (12) 11 (4, 19) 12.7 (3.1) 14 (9, 27)
47 (16) 23.7 (4.2) 34 (16) 12 (5, 20) 13.8 (3.4) 16 (9, 27)
0.12 0.044 0.13 0.57 0.013 0.034 0.011
29 (40) 19 (26) 25 (34)
36 (61) 9 (15) 14 (24)
61 (67) 12 (13) 18 (20)
5 (3, 11)
6 (2, 12)
5 (2, 8)
0.23
a
Stopped smoking for more than 6 months before the study
No significant differences were found in the SLEDAI (p = 0.20) or SLICC/ACR (p = 0.88) scores between current smokers, ex- and never-smokers (Fig. 1). Current smokers tended to have lower disease activity than ex- and never-smokers. The SLICC/ACR scores between the three groups were almost identical. Smoking, C3 and antibodies to dsDNA Current smokers had significantly lower levels of antibodies to dsDNA than ex- and never-smokers (p = 0.025, Fig. 2). The differences in the C3 levels between the groups were insignificant (p = 0.92). There was a good correlation between the anti-dsDNA results by all five assays, complement C3, and the SLEDAI score (p
