Increased expression of interleukin 1alpha and MHC class I in muscle tissue of patients with chronic, inactive polymyositis and dermatomyositis.
OBJECTIVE
To investigate if there is a molecular correlate in muscle tissue to the persisting decreased muscle function in patients with chronic, inactive polymyositis (PM) and dermatomyositis (DM).


METHODS
Muscle function was assessed using a muscle function index of myositis. To assess disease activity both histopathological investigation of muscle biopsies and magnetic resonance imaging (MRI) scans of the thigh muscles were performed. Inactive chronic disease was defined as persisting muscle weakness and absence of inflammatory infiltrates in muscle biopsy and absence of signs of inflammation on MRI. Expression of interleukin 1alpha (IL-1alpha), IL-1beta,, adhesion molecules, and MHC class I molecules in muscle tissue was investigated with immunohistochemistry.


RESULTS
Muscle weakness was confirmed by a reduction of muscle function score. No signs of inflammation typical for myositis were observed. The most striking finding in our study was the strong expression of IL-1alpha and MHC class I molecules in muscle tissue from patients with inactive chronic PM and DM. Increased IL-1alpha expression was evident in capillaries and increased MHC class I expression was detected in muscle fiber membranes.


CONCLUSIONS
IL-1alpha and MHC class I molecules may have an importance in the pathogenesis of the chronic muscle weakness and fatigue in patients with PM and DM.
Nyberg
P
P
Department of Medicine, Karolinska Institutet, Rheumatology Clinic, Karolinska Hospital, Stockholm, Sweden. pernilla.nyberg@cmm.ki.se
Wikman
A L
AL
Nennesmo
I
I
Lundberg
I
I
D000328:Adult; D001706:Biopsy; D002196:Capillaries / Q000737:chemistry / Q000378:metabolism; D002908:Chronic Disease; D003402:Creatine Kinase / Q000032:analysis; D003882:Dermatomyositis / Q000378:metabolism* / Q000473:pathology; D005260:Female; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D039041:Integrin alpha4beta1; D016023:Integrins / Q000032:analysis; D018799:Intercellular Adhesion Molecule-1 / Q000032:analysis; D007375:Interleukin-1 / Q000378:metabolism*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000032:analysis; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000737:chemistry / Q000201:enzymology; D018908:Muscle Weakness / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology; D016201:Receptors, Lymphocyte Homing / Q000032:analysis; D019010:Vascular Cell Adhesion Molecule-1 / Q000032:analysis
D015395:Histocompatibility Antigens Class I; D039041:Integrin alpha4beta1; D016023:Integrins; D007375:Interleukin-1; D016169:Lymphocyte Function-Associated Antigen-1; D016201:Receptors, Lymphocyte Homing; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1; D003402:Creatine Kinase