Erratum: Neural protection by naturopathic compounds-an example of tetramethylpyrazine from retina to brain

Abstract

Given the advantages of being stable in the ambient environment, being permeable to the blood-brain and/or blood-eye barriers and being convenient for administration, naturopathic compounds have growingly become promising therapeutic candidates for neural protection. Extracted from one of the most common Chinese herbal medicines, tetramethylpyrazine (TMP), also designated as ligustrazine, has been suggested to be neuroprotective in the central nervous system as well as the peripheral nerve network. Although the detailed molecular mechanisms of its efficacy for neural protection are understood limitedly, accumulating evidence suggests that antioxidative stress, antagonism for calcium, and suppression of pro-inflammatory factors contribute significantly to its neuroprotection. In animal studies, systemic administration of TMP (subcutaneous injection, 50 mg/kg) significantly blocked neuronal degeneration in hippocampus as well as the other vulnerable regions in brains of Sprague-Dawley rats following kainate-induced prolonged seizures. Results from us and others also demonstrated potent neuroprotective efficacy of TMP for retinal cells and robust benefits for brain in Alzheimer's disease or other brain injury. These results suggest a promising prospect for TMP to be used as a treatment of specific neurodegenerative diseases. Given the assessment of the distribution, metabolism, excretion, and toxicity information that is already available on most neuroprotective naturopathic compounds such as TMP, preclinical data to justify bringing such therapeutic compounds to clinical trials in humans is feasible.[This corrects the article on p. in vol. .].

Fig. 1

The conventional route of most natural compounds from herbs to target organs. In the traditional Chinese medicine, the herbal therapeutic ingredients are extracted and prepared as herbal tea or soup with water through regular cooking and taken orally. The effective ingredients are absorbed by the gastrointestinal tract and successfully pass through the blood–brain and/or blood–eye barriers to reach the targets, brain and/or retinas (graphic clips were taken from the Internet free sources)

Fig. 2

Systemic administration of TMP attenuates neuronal degeneration in rat brains following kainate-induced seizures. a Both hematoxylin–eosin (H & E) and TUNEL staining demonstrate massive neuronal damage shown as pink in H & E staining (f, g) and green in TUNEL (h, i, and j) in both hippocampus (f, g, h, and i) and piriform cortex (j) regions. In contrast, the animals received TMP only exhibited a few sporadic eosinophilic (l) and TUNEL-positive cells in the corresponding regions (m, n, and o). b Quantification of TUNEL-positive cells according to our previous methods reveals a significant decrease in the number of damaged neurons in the hippocampal regions with TMP treatment. Scale bar = 100 µm in b, d, e, g, i, j, l, n, and o; and 400 µm in a, c, f, h, k, and m