|LE Magazine March 2000|
Multiple agents have been proposed for the prevention and treatment of fibrosis. S-adenosylmethionine was reported to oppose CCl4-induced fibrosis in the rat, to attenuate the consequences of the ethanol-induced oxidative stress, and to decrease mortality in cirrhotics. Anti-inflammatory medications and agents that interfere with collagen synthesis, such as inhibitors of prolyl-4-hydroxylase and antioxidants, are also being tested. In nonhuman primates, polyenylphosphatidylcholine (PPC), extracted from soybeans, protected against alcohol-induced fibrosis and cirrhosis and prevented the associated hepatic phosphatidylcholine (PC) depletion by increasing 18:2 containing PC species; it also attenuated the transformation of stellate cells into collagen-producing transitional cells. Furthermore, it increased collagen breakdown, as shown in cultured stellate cells enriched with PPC or pure dilinoleoyl PC, the main PC species present in the extract. Because PPC and dilinoleoyl PC promote the breakdown of collagen, there is reasonable hope that this treatment may be useful for the management of fibrosis of alcoholic, as well as nonalcoholic, etiologies and that it may affect not only the progression of the disease, but may also reverse pre-existing fibrosis, as demonstrated for CCl4-induced cirrhosis in the rat and as presently tested in an ongoing clinical trial.
A hepatoprotective effect of PPC
Dietary iron overload damages membrane phospholipids and decreases microsomal cytochromes P-450. We wondered whether this might also pertain to cytochrome P-4502E1 (2E1) and whether polyenylphosphatidylcholine (PPC), a 94-96% pure mixture of linoleate-rich polyunsaturated phosphatidylcholines that protects against alcohol-induced liver injury, also affects 2E1, either in the presence or absence of iron. Accordingly, rats were fed for 8 weeks our standard liquid diet containing ethanol (36% of energy) or isocaloric carbohydrates, with either PPC (3 g/1000 Cal) or equivalent amounts of linoleate (as safflower oil). 2E1 was assessed by Western blots and by two of its characteristic enzyme activities: the microsomal ethanol oxidizing system (MEOS), evaluated by the conversion of ethanol to acetaldehyde (determined by head space GC), and p-nitrophenolhydroxylase (PNP) activity, measured by HPLC with UV detection of 4-nitrocatechol. With ethanol (36% of energy) replacing carbohydrates, 2E1 content increased 10-fold, with a corresponding increase in PNP and MEOS activities, but when carbonyl iron (5 g/1000 Cal) was added, the induction was significantly reduced. This iron-induced decrease was corrected by PPC. PPC is rich in linoleate, but when the latter was given as triglycerides (safflower oil), there was no effect, whereas hepatic nonheme iron content was the same in both these groups. It also was found that in the absence of iron, the ethanol-mediated induction of 2E1 and its corresponding enzyme activities were significantly less with PPC (< 0.001) than with safflower oil. In addition, in alcohol-fed animals, PPC decreased the oxidative stress (as determined by F2-isoprostanes), which reflects yet another hepatoprotective effect of PPC.
Hepatitis and PPC
BACKGROUND/AIMS: Polyunsaturated phospatidyl-choline (PPC) has been shown to reduce serum aminotransferases in experimental hepatitis. This multi-center, randomized, double-blind, placebo-controlled trial evaluated the effects of PPC in patients with chronic hepatitis B and C in combination with interferon alpha 2a or 2b. The diagnosis of chronic viral hepatitis was based on an abnormal serum alanine aminotransferase (ALT) value (more than twice the upper value of normal), viral replication and chronic hepatitis found on liver biopsy. METHODOLOGY: Patients received 5 million I.U. (Hepatitis B) and 3 million I.U. (hepatitis C) interferon s.c. thrice weekly for 24 weeks, respectively, and were randomly assigned to additional oral medication with either 6 capsules of PPC (total daily dose: 1.8 g) or 6 capsules of placebo per day for 24 weeks. Biochemical response to therapy was defined as a reduction of ALT by more than 50% of pre-treatment values. The responders were treated for further 24 weeks after cessation of interferon therapy with either PPC or placebo. RESULTS: 176 patients completed the study protocol (per-protocol population: 92 in the PPC and 84 in the placebo group). A biochemical response (> 50% ALT reduction) was seen in 71% of patients who were treated with PPC, but only in 56% of patients who received placebo (p < 0.05). PPC increased the response rate in particular in patients with hepatitis C: 71% of those patients responded in the PPC group versus 51% in the placebo group (p < 0.05). Prolonged PPC therapy given to responders beyond the cessation of interferon therapy tended to increase the rate of sustained responders at week 48 in patients with hepatitis C (41% versus 15% in the control group; p = 0.064). In contrast, PPC did not alter the biochemical response to interferon in patients with hepatitis B. PPC did not accelerate elimination of HBV-DNA, HBeAg and HCV-RNA. CONCLUSIONS: In conclusion, PPC may be recommended in patients with chronic hepatitis C in combination with interferon and after termination of interferon in order to reduce the high relapse rate. PPC may not be recommended for patients with chronic hepatitis B. In contrast to IFN and other antiviral agents PPC does not carry major risks and is tolerated very well.
Reducing Aspirin Induced Gastric Mucosal Damage
OBJECTIVE: In previous studies on rats, we have shown that aspirin (ASA)-induced injury to the gastric mucosa is markedly reduced or completely abolished if ASA is chemically associated with the phospholipid, phosphatidylcholine (PC). We have also shown that the protective effect of PC does not influence the ability of ASA to inhibit mucosal cyclooxygenase (COX) activity in the stomach and other tissues. We therefore sought to assess the effect of PC-associated ASA (ASA/PC) on the gastric mucosa of normal volunteers and to compare the results with the use of ASA alone. METHODS: Sixteen normal healthy subjects were administered ASA or ASA/PC in a randomized, double-blind, crossover study. The subjects received ASA in a dose of 650 mg three times a day for 3 days or an equivalent dose of ASA chemically associated with PC. Endoscopy was performed at baseline and again on the morning of day 4, after the subjects had taken the final dose of the test drug. On both occasions, antral biopsy specimens were obtained for the assessment of mucosal COX activity and prostaglandin concentration. RESULTS: The number (mean +/- SD) of gastric erosions seen with the ASA/PC formulation was significantly less than when ASA was used alone (8.7 +/- 10.7 vs 2.9 +/- 4.3; p < 0.025). A similar trend was seen in the duodenum but the difference was statistically not significant. The antral mucosal COX activity, as well as the level of prostaglandin 6-keto PGF1alpha, were reduced significantly (80-88%) and to a similar extent by both ASA and ASA/PC. CONCLUSIONS: The present study shows that acute aspirin-induced damage to the gastric mucosa can be reduced by chemically associating ASA with PC. The mechanism of mucosal protection provided by this compound is not related to any alteration in the ability of ASA to inhibit mucosal COX activity. We believe this protection is attributable to the maintenance of the defensive hydrophobic barrier of the gastric mucosa.
PPC and Cholesterol Uptake
Pancreatic secretion is required for efficient cholesterol absorption by the intestine, but the factors responsible for this effect have not been clearly defined. To identify factors involved and to investigate their role in cholesterol uptake, we studied the effect of Viokase(R), a porcine pancreatic extract, on cholesterol uptake into human intestinal Caco-2 cells. Viokase is capable of facilitating cholesterol uptake into these cells such that the level of uptake is 5-fold higher in the presence of solubilized Viokase. This stimulation is time-dependent and is dependent on the presence of bile salt. However, bile salt-stimulated pancreatic cholesterol esterase, which has been proposed to mediate cholesterol uptake, is not fully responsible. The major cholesterol transport activity was purified and identified as pancreatic phospholipase A2. Anti-phospholipase A2 antibodies abolished virtually all of the phospholipase A2 and cholesterol transport activity of solubilized Viokase. We demonstrate that both phospholipase A2 and cholesterol esterase increase cholesterol uptake by hydrolyzing the phosphatidylcholine that is used to prepare the cholesterol-containing micelles. In the absence of cholesterol esterase or phospholipase A2, uptake of cholesterol from micelles containing phosphatidylcholine is not as efficient as uptake from micelles containing phospholipase A2-hydrolytic products. These results indicate that phospholipase A2 may mediate cholesterol absorption by altering the physical-chemical state of cholesterol within the intestine.
Flavonoids Antioxidative Action
Antioxidative action of flavonoids have been attracted attention of many investigators and a good deal of studies on it were reported. While their interests were mostly centered to the direct scavenging action of flavonoids against free radicals and active oxygen species, we expected that the interaction of flavonoids and intracellularly occurring antioxidative agents such as glutathione peroxidase (GSH-PO) could synergistically enhance their antioxidative activities. For this purpose, cultured rat hepatocytes (BL-9), which are highly expressing GSH-PO, were employed. One group of the cells were cultured with Se deficient media (Se(-) cells) to diminish the activity and the expression of GSH-PO protein and mRNA, and the other group was cultured with Se supplemented media (Se(+) cells). The oxidative cell damage was induced by the addition of H2O2 and two representative antioxidative flavonoids, quercetin and catechin, were added to the media to test their cytoprotective action. In Se(+) cells, the remarkable cytoprotective activity of those flavonoids were confirmed, whereas none of such activity was evidenced in Se(-) cells. It was proved that the intracellular antioxidative function of flavonoids requires the interaction with GSH-PO, at least in the cells expressing the enzyme. Interestingly, the flavonoid activated GSH-PO clearly, and its mechanism is discussed.
Flavonoids as Hormones
Although for centuries plants have been known to have hormone-like actions in humans, the mechanism(s) by which plant-derived compounds act in humans is still being elucidated, a goal that has assumed more importance due to interest in the protective actions of fruits and vegetables in diseases such as cancer. Here I use the "molecular fossil record" of amino acid sequences of proteins involved in regulating the actions steroids, retinoids, thyroid hormone and prostaglandins to propose some mechanisms by which flavonoids in fruits and vegetables can have hormone-like actions in humans. I focus on: i) hormone receptors that bind to DNA and regulate gene transcription and ii) the enzymes that regulate the concentrations of these hormones. Comparative analyses of amino acid sequences show that nuclear receptors for steroids, retinoids, thyroid hormone and prostaglandins in humans and insects are descended from a common ancestor. Similar analyses of dehydrogenases that regulate the concentrations of steroids, retinoids and prostaglandins reveal strong sequence similarity to enzymes in plants, insects, fungi, and bacteria. The similarity is sufficient to suggest that some compounds that bind receptors or enzymes in invertebrates, plants or unicellular organisms may also bind to mammalian homologs that are involved in endocrine physiology. Among the phytochemicals that are candidates for such activity are flavonoids because they are involved in plant-insect and plant-bacteria interactions and have some structural and chemical similarities to steroids, retinoids, thyroid hormone, prostaglandins and fatty acids. These similarities and the kinship of human, plant, insect and bacterial proteins involved in signal transduction provide a conceptual framework for investigating flavonoids for hormone-like actions in humans. Understanding these modes of action may be useful in developing protocols for preventing.
We investigated, by measuring oxygen radical absorbance capacity (ORAC), whether hyperoxia causes alterations in antioxidant status and whether these alterations could be modulated by dietary antioxidants. Rats were fed for 8 wk a control diet or a control diet supplemented with vitamin E (500 IU/kg) or with aqueous extracts (ORAC: 1.36 mmol Trolox equivalents/kg) from blueberries or spinach and then were exposed to air or >99% O2 for 48 h. Although the constituents of the extracts were not extensively characterized, HPLC indicated that blueberry extract was particularly rich in anthocyanins, and the spinach extract did not contain any anthocyanins. The ORAC was determined in samples without proteins [serum treated with perchloric acid (PCA); ORACPCA] and with proteins (ORACtot). Hyperoxia induced a decrease in serum protein concentration, an increase in serum ORACPCA, decreases in lung ORACPCA and ORACtot, and an equilibration of proteins and ORACPCA between serum and pleural effusion. These alterations suggested a redistribution of antioxidants between tissues and an increase in capillary permeability during hyperoxia. Only the blueberry extract was effective in alleviating the hyperoxia-induced redistribution of antioxidantsbetween tissues.
Experiences in the medical treatment of progressive myopia
In order to judge the effect of anthocyanosides and vitamine E (Difrarel E) on refraction, visual acuity and eye-fundus, we treated 36 patients with this speciality in progressive myopia. After an observation period of 14.5 months an average increase of myopia by 0.53 dpt per eye was demonstrated. The final examination of 29 patients showed a stabilization of the fundus-alterations, as well as a stable, or an improved visual acuity respectively. In 7 patients a moderate deterioration of the partial or overall medical findings occurred. Our observations allow the conclusion that Difrarel E achieves therapeutically valuable results in the treatment of progressive myopia.