Melatonin, the chief hormone of the pineal gland in vertebrates, is widely distributed in the animal kingdom. Among many functions, melatonin synchronizes circadian and circannual rhythms, stimulates immune function, may increase life span, inhibits growth of cancer cells in vitro and cancer progression and promotion in vivo, and was recently shown to be a potent hydroxyl radical scavenger and antioxidant. Hydroxyl radicals are highly toxic by-products of oxygen metabolism that damage cellular DNA and other macromolecules. Herein we report that melatonin, in varying concentrations, is also found in a variety of plants. Melatonin concentrations, measured in nine different plants by radioimmunoassay, ranged from 0 to 862 pg melatonin/mg protein. The presence of melatonin was verified by gas chromatography/mass spectrometry. Our findings suggest that the consumption of plant materials that contain high levels of melatonin could alter blood melatonin levels of the indole as well as provide protection of macromolecules against oxidative damage.

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Enteric neuronal degeneration, as seen in inflammatory bowel disease, obesity, and diabetes, can lead to gastrointestinal dysmotility. Pyroptosis is a novel form of programmed cell death but little is known about its role in enteric neuronal degeneration. We observed higher levels of cleaved caspase-1, a marker of pyroptosis, in myenteric ganglia of overweight and obese human subjects compared with normal-weight subjects. Western diet-fed (WD-fed) mice exhibited increased myenteric neuronal pyroptosis, delayed colonic transit, and impaired electric field stimulation-induced colonic relaxation responses. WD increased TLR4 expression and cleaved caspase-1 in myenteric nitrergic neurons. Overactivation of nitrergic neuronal NF-κB signaling resulted in increased pyroptosis and delayed colonic motility. In caspase-11-deficient mice, WD did not induce nitrergic myenteric neuronal pyroptosis and colonic dysmotility. To understand the contributions of saturated fatty acids and bacterial products to the steps leading to enteric neurodegeneration, we performed in vitro experiments using mouse enteric neurons. Palmitate and lipopolysaccharide (LPS) increased nitrergic, but not cholinergic, enteric neuronal pyroptosis. LPS gained entry to the cytosol in the presence of palmitate, activating caspase-11 and gasdermin D, leading to pyroptosis. These results support a role of the caspase-11-mediated pyroptotic pathway in WD-induced myenteric nitrergic neuronal degeneration and colonic dysmotility, providing important therapeutic targets for enteric neuropathy.

The adsorption isotherm of a soluble anionic surfactant was measured and discussed within the framework of established thermodynamical models. The adsorbed amount derived by these models was compared with the results obtained by second harmonic generation, SHG. SHG can be used as a highly surface specific probe which allows the determination of orientation and number density. Since no thermodynamic quantities are involved in the interpretation of SHG measurements, the data can be used to assess the validity and underlying assumptions of thermodynamic adsorption models. The SHG experiments reveal a good agreement with the Frumkin model. No indication of a subsurface layer can be found.