| Objective:Vomiting is a reflex response that the gastric contents return into the esophagus, and vomit orally. Vomiting can spit out the harmful substances from the stomach, it is a kind of body's defensive and protective reflext. But in most cases, vomiting is distressing symptoms which can be modulated via multiple mechanisms operating at different loci within these systems. Generally vomiting is divided into reflective vomiting, central vomiting, vomiting of vestibular disorder and neural functionality vomiting. It involves dozens of diseases, especially during radiotherapy and chemotherapy. Vomiting can lead to dehydration or electrolyte balance disorders, which greatly reduce life quality and affect compliance in some patients. Therefore, how to effectively prevent radiotherapy or chemotherapy-induced vomiting becomes an important research subject of scientists in many countries.The current clinical antiemetic drugs commonly are chemical drugs, such as histamine, acetylcholine, dopamine, SP and other receptor antagonists. These drugs are endowed with high price, usually have many side effects and have to be given in combination with other agents. Therefore, it is required to explore a natural and low-toxic antiemetic agent, which could treat vomiting by multi-targets effect.Ginger is known as "saint drug of vomiting" which has been used as a common antiemetic drug for more than 2,000 years in China. Gingerol is the generic term of pungent constituents in ginger. To study the antiemetic mechanism of gingerol will provide useful ideas for revealing the antiemetic mystery of ginger.On the base of the past studies, we integrated the traditional pharmacology and the modern molecular biological techniques, use the new vomiting model of minks and the classic pica model of rats to investigate the antiemetic effect of gingerol and its probably mechanism in organs level and cells level from the following aspects:1. Gingerol inhibits the acute vomiting by down regulating 5-HT, DA and substance P expression in minks; 2. Effect of gingerol on NK1 receptor expression in the delayed vomiting model of minks; 3. Effect of gingerol on c-fos, NKi receptor, CCK, CGRP, MTL expression in the pica model of rats.Methods:1. Gingerol inhibits the acute vomiting by down regulating 5-HT, DA and substance P expression in minksMinks were randomly divided into the following 6 groups (n=6), the blank control group, the model group, the low-dose gingerol group, the middle-dose gingerol group, the high-dose gingerol group and the ondansetron group. Following administration of cisplatin, animals were observed continuously for 6 hours for the emetic responses, the time of onset to vomiting and the number of both retches and vomits. Animals were sacrificed 6 hours after administration of cisplatin. Tissues of the area postrema as well as the ileum were removed. The levels of 5-HT, DA and distribution of substance P in the area postrema and ileum were measured by high performance liquid chromatography (HPLC) and immunohistochemistry respectively.2. Effect of gingerol on NK1receptor expression in the delayed vomiting model of minksThe groups were divided as the first experiment. Animals were observed continuously for 72 hours for the emetic responses, the time of onset to vomiting and the number of both retches and vomits. Animals were sacrificed 72 hours after administration of cisplatin. Tissues of the area postrema as well as the ileum were removed. The levels of NK1 receptor expression in the area postrema and ileum were measured by immunohistochemistry and western-blot respectively.3. Effect of gingerol on c-fos, NK1 receptor, CCK, CGRP, MTL expression in the pica model of ratsRats were randomly divided into the following 8 groups (n=6), the blank control group, the gingerol control group, the model group, the aprepitant group, the ondansetron group, the low-dose gingerol group, the middle-dose gingerol group and the high-dose gingerol group. Following administration of cisplatin, animals were observed continuously for 72 hours for the responses and the consumption of kaolin. Animals were sacrificed 72 hours after administration of cisplatin. Tissues of the area postrema as well as the ileum were removed, the blood was sampled from the abdominal aorta. The levels of NK1 receptor expression in the area postrema and ileum were measured by RT-PCR, distribution of c-fos in the area postrema and ileum were measured by immunohistochemistry, the levels of CCK, CGRP, MTL were measured by radioimmunoassay.Results:1. Gingerol inhibits the acute vomiting by down regulating 5-HT, DA and substance P expression in minksCisplatin evoked a profound emetic response in 6 minks of the model group, pretreatment with gingerol reduced the number of retches and vomits induced by cisplatin and increased the latency of onset of cisplatin to induce emesis during the 6 h observation period (P＜0.01). And there was no significant difference on the number of retches and vomits between the high-dose group and ondansetron group (P>0.05).The immunohistochemistry and HPLC studies showed:Cisplatin produced a significant increase in 5-HT, DA and SP levels in the area postrema and ileum of minks (P<0.05), and this increase was significantly inhibited by gingerol. There was no significant difference between the 5-HT release in the area postrema of ondansetron and in the high-dose group (P>0.05), but ondansetron did not alter the 5-HT release from the mink ileum induced by cisplatin (P>0.05), nor did ondansetron to DA and SP release from the mink ileum as well as the area postrema induced by cisplatin (P>0.05).2. Effect of gingerol on NK1 receptor expression in the delayed vomiting model of minksMinks dosed with vehicle followed by cisplatin had two distinct periods of retching and vomiting. There was an initial acute phase, which typically reached the peak at 24 h after dosing with cisplatin. After this period there was a delayed phase in 24-72 h (P＜0.05). Gingerol decreased the retching and vomiting response during the 72 h observation period with significant decreases observed on each of the three test days (P<0.01). Ondansetron significantly decreased the retching and vomiting response during 24 h following cisplatin injection (P<0.05). However, there was no significant decreases on the retching and vomiting response during 24-72 h (P>0.05).The immunohistochemistry and Western-blot studies showed: The expression levels of NK1 receptor significantly increased after treatment with cisplatin (P<0.01), the elevated expression was inhibited by the pretreatment of gingerol in both the ileum and area postrema in a dose-dependent manner (P＜0.01). However, ondansetron had no significant effect on the elevated level of NK1 receptor protein in either the area postrema or ileum (P>0.05).3. Effect of gingerol on c-fos, NK1 receptor, CCK, CGRP, MTL expression in the pica model of ratsRats in model group followed by cisplatin had two distinct periods of consumption of kaolin. There was an initial acute phase, which typically reached its peak at 24 h after dosing with cisplatin (P<0.01), and there was a delayed phase in 24-72 h which the consumption of kaolin was decreasing. Gingerol decreased the consumption of kaolin during the 72 h observation period (P<0.01). Ondansetron significantly decreased the consumption of kaolin during 24 h following cisplatin injection (P<0.01). However, there was no siginificant decreases during 24-72 h (P>0.05). Aprepitant decreased the consumption of kaolin either in the acute phase or the delayed period (P<0.05).The immunohistochemistry research showed:The expression levels of c-fos significantly increased after treatment with cisplatin (P<0.05), the elevated expression was inhibited by the pretreatment of gingerol in both the ileum and the area postrema in a dose-dependent manner (P<0.05). Ondansetron and aprepitant had no significant effect on the elevated level of c-fos protein in either the area postrema or ileum (P>0.05).The results of RT-PCR showed:The expression levels of NK1's mRNA significantly increased after treatment with cisplatin (P<0.05), the elevated expression was inhibited by the pretreatment of gingerol in both the ileum and area postrema in a dose-dependent manner (P＜0.05). Ondansetron had significant effect on the elevated level of NK1's mRNA neither in the area postrema nor in ileum (P>0.05). Aprepitant significantly decreased the elevated levels of NK1's mRNA in both the ileum and area postrema (P<0.05).The results of radioimmunoassay indicated: The levels of CCK, CGRP, MTL significantly increased after treatment with cisplatin (P<0.05), the elevated levels were inhibited by the pretreatment of gingerol in a dose-dependent manner (P<0.05). Ondansetron and aprepitant had no significant effect on the elevated level of CCK, CGRP, MTL (P＞0.05).Conclusions:1. Cisplatin could evoke the acute vomiting in minks and cause a significant increase in 5-HT, DA and SP levels in postrema and ileum. Gingerol can antagonize the cisplatin-induced emesis of minks in acute phase possibly by inhibiting central or peripheral increase of 5-HT, DA and substance P.2. Cisplatin could produce the delayed vomiting in minks and increase the expression of NK1 receptor in the area postrema and ileum. Gingerol can counteract cisplatin-induced emesis of minks in delayed period possibly by inhibiting central or peripheral increase of NK1 receptors in a dose-dependent manner.3. Cisplatin could replicate the pica model of rats and increase the expression of NK1 receptor, c-fos, CCK, CGRP, MTL in the area postrema and ileum. Gingerol could decrease cisplatin-induced consumption of kaolin in rats; this may be related to inhibiting central or peripheral increase of c-fos protein and NK1 receptors and the levels of CCK, CGRP, MTL in a dose-dependent manner. |
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