PHKB

Prostaglandin D2 (PGD2)

Prostaglandin D2 (PGD2) is a bioactive lipid compound that belongs to the family of prostaglandins, which are derived from arachidonic acid. PGD2 is a member of the eicosanoid family and plays a significant role in various physiological and pathological processes in the human body.

Biochemistry

PGD2 is synthesized from arachidonic acid through the cyclooxygenase (COX) pathway. The enzyme prostaglandin D synthase (PGDS) catalyzes the conversion of prostaglandin H2 (PGH2) to PGD2. There are two main types of PGDS: lipocalin-type PGDS (L-PGDS) and hematopoietic PGDS (H-PGDS), each with distinct tissue distributions and functions.

Physiological Roles

PGD2 is involved in a variety of physiological processes, including:

• Sleep Regulation: PGD2 is known to promote sleep and is involved in the regulation of the sleep-wake cycle. It acts on the central nervous system to induce sleepiness.

• Inflammation and Immune Response: PGD2 is a potent mediator of inflammation and is produced by mast cells during allergic reactions. It plays a role in the recruitment of eosinophils and other immune cells to sites of inflammation.

• Bronchoconstriction: PGD2 is involved in the pathophysiology of asthma and other respiratory conditions by causing bronchoconstriction and increasing mucus production.

• Hair Growth: PGD2 has been implicated in the regulation of hair growth and is thought to play a role in androgenetic alopecia.

Receptors

PGD2 exerts its effects through binding to specific G protein-coupled receptors (GPCRs), primarily the DP1 and DP2 (also known as CRTH2) receptors. These receptors are expressed in various tissues and mediate the diverse actions of PGD2.

• DP1 Receptor: Activation of the DP1 receptor generally leads to vasodilation and inhibition of platelet aggregation.

• DP2 Receptor (CRTH2): The DP2 receptor is involved in the chemotaxis of Th2 cells, eosinophils, and basophils, contributing to allergic inflammation.

Clinical Significance

Due to its role in inflammation and allergic responses, PGD2 is a target for therapeutic intervention in conditions such as asthma, allergic rhinitis, and other inflammatory diseases. Inhibitors of PGD2 synthesis or receptor antagonists are being explored as potential treatments.

Research and Developments

Recent studies have focused on the role of PGD2 in hair loss, particularly in male pattern baldness. Research is ongoing to develop PGD2 receptor antagonists as potential treatments for hair loss.

Also see

• Prostaglandin E2
• Cyclooxygenase
• Eicosanoids
• Mast cells
• Arachidonic acid