S100A8 in Serum and Urine as a New Biomarker in Lupus Nephritis

Systemic lupus erythematosus (SLE) is a systemic autoimmune/ inflammatory disease that can affect any organ of the human body. The molecular pathophysiology of SLE remains largely unknown, but complex interactions of genetic factors, the environment, and hormones contribute to disease expression.

Clinical importance of S100 calcium-binding protein A8 protein (S100A8) as a biomarker in SLE has been well-established. During an inflammatory reaction, neutrophils produce S100A8, a Ca2+-binding protein that is part of the S100 family and is found in neutrophil extracellular traps.

In addition to its primary role as a member of the S100A8/A9 heterodimer, S100A8 accumulates in various bodily compartments and functions as a damage-associated molecular pattern molecule upon release. It is a crucial regulator of inflammation and enhances the function of innate immune cells by interacting with members of the immunoglobulin superfamily of cell surface molecules, such as toll-like receptor 4 and the receptor of advanced glycation end products.

Serum S100A8 levels are linked with disease activity, glomerulonephritis, and anti-double-stranded DNA (dsDNA) antibodies (Ab), according to increasing experimental and clinical data. healthy controls (HCs) had lower serum S100A8 levels. Considering that elevated blood S100A8 levels are also seen in several inflammatory disorders such as inflammatory bowel disease and rheumatoid arthritis, it is unclear if this elevated level is adequate to serve as a biomarker specific to SLE.

Inclusion criteria

• Age ≥ 18 years.
• Both sexes.
• Patients with Systemic lupus erythematosus (SLE)
• Patients with SLE and renal affection. SLE diagnosis is based on the 1997 American College of Rheumatology (ACR) criteria or the 2012 Systemic Lupus International Collaborating Clinics (SLICC) classification criteria.

Renal involvement (lupus Nephritis) (LN) can be diagnosed by presence of proteinurea or elevated kidney function and can be confirmed by biopsy if present.

Exclusion criteria

• Autoimmune diseases.
• Sjogren's syndrome.
• Rheumatoid arthritis.
• Systemic sclerosis.
• Taking other biologic disease-modifying anti-rheumatic drugs.
• Immunosuppressive drugs.
• Corticosteroid.