Prostaglandins are special tissue hormones. They are also used in drugs.
What are prostaglandins?
Prostaglandins are local hormones from the eicosanoid class derived from arachidonic acid. They are important for the local mediation of pain. In addition, they serve as mediators of hormone action and are involved in integrative functions. The name prostaglandins is due to the discovery of the hormones in prostatic secretions. However, tissue hormones are present in almost all human organs. In doing so, they influence numerous bodily processes. Prostaglandins are unsaturated fatty acids. They are composed of 20 carbon atoms, which have a ring of five CA atoms in their center. Different fatty acids act as starting materials for their synthesis.
Function, action, and roles
Prostaglandins also bear the name tissue hormones. Thus, unlike other hormones, they are not formed in a gland, but are produced in the tissues of the body in response to various stimuli. Prostaglandins are produced from fatty acids such as arachidonic acid, which also involves the enzyme cyclooxygenase (COX). After production, the tissue hormones are released in the immediate vicinity of the tissue that produced them, where they are active for a short period of time. A distinction is made between different endogenous prostaglandins, several groups of which are produced. These include PGF, PGE and PGD, which in turn are subdivided into subgroups. The effects of the prostaglandins are extremely diverse and often even different. The main groups are considered to be the series 1 prostaglandins, the series 2 prostaglandins, and the series 3 prostaglandins. Series 1 prostaglandins originate from dihomogammalinolenic acid (DGLA). Their functions include reducing blood clotting and inhibiting inflammation. Series 2 prostaglandins arise from arachidonic acid (AA). Their action is opposite to that of series 1 prostaglandins, which means that they cause and even increase inflammation. They also trigger greater blood clotting, increase the perception of pain, and cause blood vessels to constrict. In doing so, they cause effects that are necessary to counteract injuries or wounds. Series 3 prostaglandins are tissue hormones derived from eicosapentaenoic acid. One of their functions is to reduce the formation of series 2 prostaglandins. Therefore, they are considered anti-inflammatory.
Formation, occurrence, properties, and optimal values
The various prostaglandins, unlike other hormones, are found almost everywhere in the body. First and foremost, this includes the male sperm. The synthesis of tissue hormones is also dependent on food. Thus, most prostaglandins are derivatives of arachidonic acid, which in turn belongs to the omega-6 fatty acids. Phospholipids act as a reservoir for the formation of prostaglandins. These are contained in the membranes of cells, from which they are cleaved by the effect of PLA2 (phospolipase 2). A subsequent effect of cyclooxygenases 1 and 2 ensures the formation of prostaglandins. The prostaglandin, which is initially formed by the cyclooxygenase effect, is called PGG2. Due to a further transformation, it gives rise to PGH2, which in turn serves as the starting point of various substances that are biologically active. These include PGE2, PGD2, prostacyclin (PGI2), PGF2, and thromboxane (TXA2), among others. Analogues of prostaglandins can also be used in medicine to produce drugs. These include, for example, alprostadil, a prostaglandin E1 analogue used to dilate peripheral arteries. The prostaglandin E2 analog dinoprostone is used to promote labor at the end of pregnancy. Other medications include the prostaglandin E1 analog misoprostol, used to prevent and treat gastric and duodenal ulcers, and the prostaglandin E2 analog sulprostone, which stimulates labor.
Diseases and disorders
The beneficial effects of prostaglandins are of great importance in medicine and can be used for targeted treatments. Thus, both endogenous prostaglandins and derivatives whose chemical modification occurs are used.For example, the drug dinoprostone, which is used in obstetrics, corresponds to the body’s own tissue hormone PGE2. Synthetic prostaglandin derivatives such as gemeprost or sulprostone are also administered in obstetrics. They have the effect of dilating the cervix and contracting the muscles of the uterus. The endogenous prostaglandin PGF2-alpha gives rise to the active ingredients bimatoprost, latanoprost, travoprost and tafluprost, which are used to treat glaucoma. They dilate the aqueous humor outflow ducts within the eye’s cornea. The drugs alprostadil and iloprost improve blood flow in certain regions of the body. While alprostadil corresponds to the prostaglandin PGE1, iloprost is a synthetic derivative. However, some prostaglandins, such as PGE2, also cause adverse health effects. These include pain, inflammation and fever. However, it is possible to suppress the production of these tissue hormones with the help of non-opioid painkillers such as anti-inflammatory drugs or acetylsalicylic acid. They have the property of blocking the COX enzyme. This is essential for prostaglandin production. By inhibiting cycloooxygenase, the production of prostaglandins is no longer possible. The prostaglandins are usually administered in the form of injections. However, they can also be applied locally in vagina gels, eye drops, inhalants or urethral sticks. Prostaglandins interact with drugs that have a prostaglandin-inhibiting effect. These are primarily non-steroidal anti-inflammatory drugs and anti-inflammatory drugs. They weaken the effect of the tissue hormones. In contrast, an enhancement of prostaglandin effects is possible with other agents.
