Polyphenols in the treatment of autoimmune diseases

Abstract

In addition to protecting body from infections and diseases, the immune system produces auto-antibodies that can cause complex autoimmune disorders, such as Type I diabetes, primary biliary cirrhosis, rheumatoid arthritis, and multiple sclerosis, to name a few. In such cases, the immune system fails to recognize between foreign agents and its own body cells. Different factors, such as genetic factors (CD25, STAT4), epigenetic factors (DNA methylation, histone modifications) and environmental factors (xenobiotics, drugs, hormones) trigger autoimmunity. Glucocorticoids, non-steroidal anti-inflammatory drugs (NSAIDs), immunosuppressive and biological agents are currently used to manage autoimmune diseases of different origins. However, complete cure remains elusive. Many dietary and natural products including polyphenols have been widely studied as possible alternative treatment strategies for the management of autoimmune disorders. Polyphenols possess a wide-range of pharmacological and therapeutic properties, including antioxidant and anti-inflammatory activities. As immunomodulatory agents, polyphenols are emerging pharmaceutical tools for management of various autoimmune disorders including vitiligo, ulcerative colitis and multiple sclerosis (MS). Polyphenols activate intracellular pathways such as arachidonic acid dependent pathway, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway, mitogen-activated protein kinases (MAPKs) pathway, phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling pathway and epigenetic modulation, which regulate the host's immune response. This timely review discusses putative points of action of polyphenols in autoimmune diseases, characterizing their efficacy and safety as therapeutic agents in managing autoimmune disorders.

Keywords: Autoimmunity; Epigenetic modulation; MAPKs; NF-κB; PI3K/Akt; Polyphenols.

Figure 1

The factors that influence the development of autoimmunity.

Figure 2

Main proposed points of action of polyphenols in autoimmune diseases (+ means activation and - inhibition. Akt, protein kinase B; COX, cyclooxygenase; ERK-1/2, extracellular-signal-regulated kinases 1/2; IκBs, inhibitory proteins of κB; IKK, IκBs kinase; JNKs, c-Jun amino-terminal kinases; LOX, lipoxygenase; MAPKs, mitogen-activated protein kinases; p38, p38-mitogen-activated protein kinase; PI3K, phosphatidylinositol 3-kinase; PLA₂, phospholipase A2; PTEN, phosphatase and tensin homolog; SIRT1, sirtuin 1.

Figure 3

Chemical structures of polyphenols used in clinical studies