In autocrine secretion, glands release messenger substances to the environment and reabsorb them themselves through receptors. This process plays a role in immune responses as well as cell growth, differentiation, and regeneration. Meanwhile, cancer is associated with dysregulation in autocrine secretion.
What is autocrine secretion?
In autocrine secretion, glands release second messengers to the environment and reabsorb them themselves through receptors. Figure shows the pancreas releasing insulin. Autocrine secretion is one of numerous secretion mechanisms in the human body. A secretion is the product of a gland or gland-like cell and can perform various tasks. In autocrine secretion, the glands or gland-like cells release hormones or hormone-like substances into the environment, which they themselves reabsorb. This process plays a role, for example, in the secretion of growth factors. These growth factors are proteins that influence cell development and, in the human organism, act particularly often on the secreting glandular cells themselves. Each secretion is either endocrine or exocrine. Endocrine secretions are transported to target cells via the blood. Unlike endocrine secretion, in autocrine secretion the blood does not serve as a transport medium for the substances produced. Rather, the action of autocrine secretions remains confined to the immediate environment, as is the case with paracrine secretion. Thus, autocrine secretion should be interpreted as a special case of paracrine secretion, and in this context, it is mainly relevant for growth factors.
Function and task
In the secretory mode of autocrine secretion, gland-like cells or glands release their secretions into the interstitial spaces between organs or tissues in the immediate environment. Autocrine glands are equipped with specific receptors to which their own secretions bind. In this way, the substances released act on the gland cells themselves. As a regulatory mechanism, the so-called ultrashort feedback mechanism is related to this. By binding to the gland receptors, the released hormone can, for example, inhibit its own secretion. This mechanism corresponds to a control loop. Autocrine action is exhibited by numerous cytokines and tissue hormones in humans. In medicine, cytokines are regulatory proteins that play a role in controlling immune responses, for example. In general, all hormones and cytokines are extracellular messengers and thus designed to act outside the releasing cell. An intracellular response, as in autocrine secretion, can only be triggered if cellular proteins are laid down as receptors in the membrane of the producing cells. These receptor proteins interact with the messenger. They are also called integral membrane proteins, cytoplasmic proteins or nuclear proteins. The interaction hormone-receptor complex stimulates the production of an intracellular signaling molecule through signal transduction. Since signal transduction occurs in multi-step processes, this is also referred to as a signal cascade. The termination of the respective cell response to a hormonal stimulus is realized by the inactivation of the intracellularly produced signal molecules. This process is also referred to as signal deletion. Hormones such as insulin, for example, act in this way as autocrine secretions, exhibiting regulatory patterns of ultrashort feedback. The mechanism of autocrine secretion thus regulates hormone balance in the broadest sense. Hormones are signaling substances that trigger a biologically specific response in cells. They thus serve to transmit information and perform irreplaceably important tasks in immunological information transmission, for example. The autocrine gland cells organize the transmission of information, so to speak. In addition to receptors, they possess their own downstream signal transmission system, which triggers a signal-specific and cell-internal response. Either this response corresponds to a positive or a negative response. In individual cases, for example, this increases the receptivity of the cells involved to other signals. Autocrine secretion also controls the differentiation processes of many tissues and cell types.It controls growth processes and plays a role in both embryogenesis and tissue regeneration.
Diseases and disorders
Diseases such as benign and malignant prostatic lesions may be related to dysregulation of autocrine secretion. Epithelial cell growth is controlled by autocrine secretions as regulatory mechanisms. For example, prostate cells are autostimulated by fibroblast growth factor as well as transforming growth factor. Both growth factors are produced directly in the cells of the prostate and influence growth based on androgen levels in different ways. For example, autocrine secretion triggers growth arrest or cell death. In the case of excessive growth processes of the prostate, this regulatory process is disturbed or misdirected. Because of these interrelationships, autocrine secretion occupies a special place in cancer research. Due to the growth control of autocrine secretions, the growth of a tumor is largely independent of external factors. Therefore, to successfully contain tumor growth, the approach from within would be recommended. This approach from the inside corresponds to an inhibition of autocrine growth factors, which stimulate the growth of the tumor in the first place. Inhibition of autocrine growth factors can be achieved by the administration of monoclonal antibodies. This therapeutic route is being discussed in modern research as a promising treatment option for cancer. Defects in the signaling cascade of autocrine secretions are now thought to be an important causative factor in all cancers. What causes such defects has not yet been conclusively clarified. Both genetic predispositions and environmental toxins may play an increased role in the misregulations.
