Myotonic and repetitive discharges in hypokalemic myopathy associated with glycyrrhizin-induced hypochloremia

Glycyrrhiza glabra

Liquorice foliage

Licochalcone A, a polyphenol present in licorice, suppresses UV-induced COX-2 expression by targeting PI3K, MEK1, and B-Raf

Licorice is a traditional botanical medicine, and has historically been commonly prescribed in Asia to treat various diseases. Glycyrrhizin (Gc), a triterpene compound, is the most abundant phytochemical constituent of licorice. However, high intake or long-term consumption of Gc has been associated with a number of side effects, including hypertension. However, the presence of alternative bioactive compounds in licorice with anti-carcinogenic effects has long been suspected. Licochalcone A (LicoA) is a prominent member of the chalcone family and can be isolated from licorice root. To date, there have been no reported studies on the suppressive effect of LicoA against solar ultraviolet (sUV)-induced cyclooxygenase (COX)-2 expression and the potential molecular mechanisms involved. Here, we show that LicoA, a major chalcone compound of licorice, effectively inhibits sUV-induced COX-2 expression and prostaglandin E2 PGE₂ generation through the inhibition of activator protein 1 AP-1 transcriptional activity, with an effect that is notably more potent than Gc. Western blotting analysis shows that LicoA suppresses sUV-induced phosphorylation of Akt/ mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinases (ERK)1/2/p90 ribosomal protein S6 kinase (RSK) in HaCaT cells. Moreover, LicoA directly suppresses the activity of phosphoinositide 3-kinase (PI3K), mitogen-activated protein kinase kinase (MEK)1, and B-Raf, but not Raf-1 in cell-free assays, indicating that PI3K, MEK1, and B-Raf are direct molecular targets of LicoA. We also found that LicoA binds to PI3K and B-Raf in an ATP-competitive manner, although LicoA does not appear to compete with ATP for binding with MEK1. Collectively, these results provide insight into the biological action of LicoA, which may have potential for development as a skin cancer chemopreventive agent.

Correlation between high intake of glycyrrhizin and myolysis of the papillary muscles: an experimental in vivo study

The ingestion of large quantities of glycyrrhizin, whether as a drug or a sweetener, is known, in susceptible subjects, to induce a syndrome similar to hypermineralcorticoidism, with bouts of hypertension, hypokaliaemia and rabdomyolysis, sometimes associated with severe renal failure and hypokaliaemia-induced arrythmias. Glycyrrhizin is also known to isomerize into the glycyrrhetic (or glycyrrhetinic) acids 18alpha- and 18beta-. In previous works, we reported that these metabolites cause bouts of hypertension and reduction in diuresis at low doses in the rat. In particular, the alpha isomer causes significant elimination of the calcium ion in the urine. The present findings confirm that 18alpha-glycyrrhetic acid is more toxic than either glycyrrhizin or the beta isomer. Histopathological study of tissue samples taken from rats treated with the alpha isomer also reveal selective damage to the myocardium with oedema, myolysis, apoptosis and blistering of the sarcoplasm. These effects begin to appear in the course of subchronic treatment, they manifest themselves in acute treatment and correlate closely with the electrocardiographic changes recorded in rats acutely treated with 18alpha-glycyrrhetic acid.

Histopathologic and MRI findings in hypokalemic myopathy induced by glycyrrhizin

Histopathologic studies and magnetic resonance images of the leg muscles were conducted in two patients with glycyrrhizin-induced hypokalemic myopathy (GHM). Muscle biopsy showed myopathic changes and vacuolated fibers with light microscopy, and dilatation of the sarcoplasmic reticulum, various types of vacuoles and myofibrillar degeneration with electron microscopy. High signal intensities in T2-weighted images obtained during severe muscle weakness were widely distributed in the leg muscles, especially the pretibial and soleus muscles. These high signal intensities disappeared after full recovery of muscle weakness. We suggest that high signal intensity in T2-weighted images can be seen and correspond to histopathologic changes in the muscles of GHM patients.