Role of Beta-Endorphin in the Skin

hormone cortisol, the melanocyte-stimulating hormone (MSH) that is involved in skin pigmentation and beta-endorphin that comprises the 31 C-terminal amino acids. POMC and its cleavage products are produced mainly in the hypothalamus and in the anterior lobe of the pituitary gland. There are several functions for beta-endorphin described. Binding with its N-terminus to the three opioid receptors mu, kappa and delta (preference for mu) leads to morphine-like effects. Beta-endorphin produces analgesia by acting on both, central and peripheral opioid receptors which inhibits the transmission of the signal along nerve cells from the source of the pain (nociceptor) to the spinal cord. Beta-endorphin was also found to bind to receptors on cells of the immune system. It seems to be involved in the fine tuning of the immune response. Finally there is strong evidence that endorphins are connected with »pleasure centres« in the brain. � Endorphins: Structure and Function Morphin, a substance found in Papaver somniferum, has an analgesic effect. Our body produces compounds with a similar effect and this is why they are called endogenous opioids. This is a group of peptide hormones comprising beta-endorphin, enkephalin and dynorphin. They share the N-terminal amino acid sequence Tyr-Gly-Gly-Phe-X (X = Met or Leu). This is the binding sequence to the opioid receptor. Each of these peptide hormones is produced out of a separate precursor peptide. Beta-endorphin is a cleavage product of proopiomelanocortin (POMC), a protein with 267 amino acid residues. Processing of POMC leads to several peptide hormones with different functions (Fig. 1): the adrenocorticotropic hormone (ACTH), also known as corticotrophin, that stimulates the adrenal cortex to secrete the anti-inflammatory and anti-allergic BETA-ENDORPHIN