What is psoriasis-associated arthritis?

Psoriasis-associated arthritis, also known as psoriatic arthritis (PsA), is a type of inflammatory arthritis that affects some individuals with psoriasis, a chronic autoimmune skin condition characterized by red, scaly patches of skin. Psoriasis-associated arthritis is classified as a seronegative spondyloarthropathy, a group of conditions that share similar features and often involve inflammation of the spine and peripheral joints.


Psoriatic arthritis can affect various parts of the body, including the joints, spine, tendons, and entheses (the sites where tendons or ligaments attach to bone). It is characterized by inflammation, pain, swelling, and stiffness in the joints, as well as other symptoms such as fatigue and nail changes. Psoriatic arthritis can vary widely in severity and may progress over time, leading to joint damage and functional impairment if left untreated.


There are several distinct subtypes of psoriatic arthritis, each with its own pattern of joint involvement and clinical features:


  • Symmetric arthritis: Involves symmetric involvement of joints, similar to rheumatoid arthritis. It typically affects multiple small joints in the hands and feet.


  • Asymmetric arthritis: Involves inflammation of one or a few joints, which may occur in an asymmetric pattern. It commonly affects the fingers and toes but can involve any joint.


  • Spondylitis: Involves inflammation of the spine and sacroiliac joints, leading to stiffness and pain in the lower back and buttocks. Spondylitis can also cause inflammation of the neck and upper back.


  • Enthesitis: Involves inflammation of the entheses, leading to pain and tenderness at sites where tendons or ligaments attach to bone, such as the heel (Achilles tendon) or bottom of the foot (plantar fascia).


  • Dactylitis: Involves inflammation of an entire digit, resulting in swelling of the entire finger or toe, giving it a sausage-like appearance.


The exact cause of psoriatic arthritis is not fully understood, but it is believed to involve a combination of genetic, environmental, and immunological factors. Genetic predisposition plays a significant role, as psoriatic arthritis tends to run in families. Environmental factors such as infections, trauma, and stress may trigger or exacerbate the condition in susceptible individuals. Immunologically, psoriatic arthritis is characterized by dysregulation of the immune system, leading to inflammation and tissue damage in the joints and other affected tissues.


What is the relationship between PsA and oxidative stress?

The relationship between psoriasis-associated arthritis (PsA) and oxidative stress is an area of growing interest in research. Oxidative stress occurs when there is an imbalance between the production of reactive oxygen species (ROS) and the body’s antioxidant defenses, leading to cellular damage. Several factors related to PsA can contribute to oxidative stress, which may in turn exacerbate inflammation, tissue damage, and joint pathology:


  • Inflammatory Pathways: PsA is characterized by chronic inflammation in the joints and surrounding tissues. Inflammatory processes generate ROS as byproducts, which can further perpetuate inflammation and oxidative stress. ROS can activate inflammatory signaling pathways, leading to the production of pro-inflammatory cytokines and chemokines, recruitment of immune cells, and tissue destruction.


  • Immune Dysregulation: PsA is an autoimmune condition characterized by dysregulation of the immune system, resulting in abnormal activation of immune cells and production of autoantibodies. Immune dysregulation can lead to increased production of ROS by activated immune cells, such as neutrophils and macrophages, contributing to oxidative stress and tissue damage in the joints.


  • Synovial Inflammation: In PsA, inflammation affects the synovium, the membrane lining the joints. Synovial inflammation is associated with increased ROS production and oxidative stress within the joint microenvironment. ROS can stimulate synoviocyte proliferation, induce expression of pro-inflammatory mediators, and promote cartilage and bone destruction.


  • Mitochondrial Dysfunction: Mitochondria, the cellular organelles responsible for energy production, play a crucial role in regulating oxidative stress. Dysfunctional mitochondria can produce excessive ROS, leading to oxidative damage and cellular dysfunction. Mitochondrial dysfunction has been implicated in the pathogenesis of various rheumatic diseases, including PsA, and may contribute to oxidative stress in affected tissues.


  • Environmental Triggers: Environmental factors such as smoking, pollution, and UV radiation can exacerbate oxidative stress in individuals with PsA. These environmental triggers can promote ROS production and impair antioxidant defenses, further contributing to oxidative damage and inflammation in the joints.


  • Systemic Inflammation: PsA is associated with systemic inflammation, characterized by elevated levels of inflammatory markers in the blood and increased oxidative stress systemically. Systemic inflammation can contribute to endothelial dysfunction, oxidative damage to vascular tissues, and increased cardiovascular risk in individuals with PsA.