The autonomy of different aspects of Sjögren´s syndrome and their treatment in an experimental model: the use of comprehensive biomarker analyses to characterize the disease and the effect of heat-shock proteins in treatment intervention

Sjögren’s syndrome (SS) is a systemic rheumatic disease, in which the salivary and lacrimal
glands are the principal targets of a pathological autoimmune reaction. Clinically, SS is
manifested by keratoconjunctivitis sicca (dry eyes) and xerostomia (dry mouth).
Histopathologically, the disease is characterized by persistent focal mononuclear cell
infiltration in the salivary glands. Traditionally, loss of secretory capacity, degree of lymphoid
infiltration and production of specific autoantibodies were anticipated to correlate with each
other and indicate disease state and disease severity. The correctness of this assumption was,
however, difficult to prove.
The aim of the first study was to clarify the chronology of the SS disease course and to
describe possible interrelationships between sialoadenitis and hyposalivation. We could
confirm that the SS in non-obese diabetic (NOD) mice is characterized by at least two distinct
phases. In our study, inflammation of the salivary glands preceded the onset of hyposalivation
with a considerable amount of time. Interestingly, the onset of hyposalivation was not
associated with a significantly higher degree of inflammation. Significant alterations in
cytokines in serum and saliva paralleled the transition from the pre-clinical to the overt
disease state.
The purpose of the second study was to acquire knowledge on 87 immunologically relevant
proteins measured in serum and 75 proteins analyzed in saliva. Thirty-eight biomarkers
analyzed in serum and 34 proteins in saliva from NOD mice were significantly altered when
compared to Balb/c mice. Eighteen biomarkers in serum and 3 chemokines in saliva had the
potential to predict individual strain-membership with 80-100% accuracy. Computation of a
correlation network led to the conclusion that processes related to the adaptive immune
system promote SS with a strong implication of T-helper (TH)2 related proteins in
hyposalivation. In addition, the SS-related disease manifestations appeared to be associated
with different immunological processes and did not correlate with each other. Cluster of
differentiation (CD)40, CD40L, interleukin-18, granulocyte chemotactic protein-2 (GCP-2)
and anti-muscarinic M3 receptor immunoglobulin G3, may, however, interrelate the different
aspects of SS. The study further established saliva as an attractive biofluid for biomarker
discovery in SS and provides a basis for the comparison and selection of potential drug targets
and diagnostic markers.
The third study was conducted to investigate a potential immunomodulatory effect of heatshock
protein 60kDa (Hsp60) and Hsp60-derived peptide aa437-460 (aa437-460)
immunization on spontaneous experimental SS. Administration of Hsp60 and aa437-460
significantly reduced SS-related histopathology compared to the untreated NOD controls. In
addition, 50% of Hsp60 and 33% of aa437-460 injected mice retained normal exocrine
function. Both treatments induced similar changes in the biomarker profiles, which indicated
decreased inflammatory chemotaxis and strengthened anti-inflammatory regulatory pathways.
Successful prevention of hyposalivation was accompanied by quantitative alterations in 36
biomarkers, of which 19 inflammatory mediators declined to levels comparable to the
measurements obtained in Balb/c mice. Molecules involved in inflammatory chemotaxis,
neovascularization and regulatory pathways coined the differences displayed by the biomarker
profiles. In addition, specific biomarker signatures had the capability to accurately predict the
received treatment, treatment efficacy and impaired exocrine function.
Common to all three studies were the appearing independence of the different aspects of SS
and the valuable information we could extract from biomarker analyses especially in saliva