Qibing Mei

Intestinal Absorption and First-Pass Metabolism of Polyphenol Compounds in Rat and Their Transport Dynamics in Caco-2 Cells

Background Polyphenols, a group of complex naturally occurring compounds, are widely distributed throughout the plant kingdom and are therefore readily consumed by humans. The relationship between their chemical structure and intestinal absorption, transport, and first-pass metabolism remains unresolved, however. Methods Here, we investigated the intestinal absorption and first-pass metabolism of four polyphenol compounds, apigenin, resveratrol, emodin and chrysophanol, using the in vitro Caco-2 cell monolayer model system and in situ intestinal perfusion and in vivo pharmacokinetic studies in rats, so as to better understand the relationship between the chemical structure and biological fate of the dietary polyphenols. Conclusion After oral administration, emodin and chrysophanol exhibited different absorptive and metabolic behaviours compared to apigenin and resveratrol. The differences in their chemical structures presumably resulted in differing affinities for drug-metabolizing enzymes, such as glucuronidase and sulphatase, and transporters, such as MRP2, SGLT1, and P-glycoprotein, which are found in intestinal epithelial cells.

Characterizations and anti-tumor activities of three acidic polysaccharides from Angelica sinensis (Oliv.) Diels.

In this study, three acidic polysaccharides (APS-3a, APS-3b and APS-3c) were obtained from Angelica sinensis (Oliv.) Diels. They displayed different structural features and anti-tumor activities. APS-3b and APS-3c significantly inhibited the growth of S180 tumors and increased the life spans of S180 tumor-bearing mice, whereas APS-3a had no significant effect. Further experiments showed that APS-3b and APS-3c could cause a concentration-dependent proliferation of the splenocytes, up-regulate IFN-gamma, IL-2 and IL-6 mRNA expressions in splenocytes and stimulate the productions of NO and TNF-alpha in peritoneal macrophages. Taken together, the three acidic polysaccharides displayed different anti-tumor activities which were associated with their different structural characteristics.

Amlodipine inhibits TNF-α production and attenuates cardiac dysfunction induced by lipopolysaccharide involving PI3K/Akt pathway

Calcium channel blockers (CCBs) are widely used in the therapy of cardiovascular diseases. Recent studies have shown that several CCBs exerted distinct anti-inflammatory effect in myocardial dysfunction models. The purpose of the present study was to evaluate therapeutic effect and possible mechanism of action of amlodipine, one of the widely used CCBs, on rat cardiac dysfunction during sepsis induced by lipopolysaccharide (LPS). Pretreatment of the rats with amlodipine (10 or 30 mg/kg, i.v.) delayed the fall of mean arterial blood pressure caused by LPS. Amlodipine also significantly inhibited the elevation of plasma tumor necrosis factor alpha (TNF-alpha) and decreased levels of inducible nitric oxide synthase (iNOS) in response to LPS challenge. To investigate the mechanism of the action of amlodipine, neonatal rat cardiomyocytes were used as a model. Amlodipine concentration-dependently decreased the release of TNF-alpha and iNOS protein expression, and suppressed the degradation and phosphorylation of inhibitor of kappaB-alpha (IkappaB-alpha) in LPS-activated neonatal rat cardiomyocytes. Further studies revealed that amlodipine markedly activated phosphatidylinositiol 3-kinase (PI3K) and Akt, downstream of the PI3K signal cascade. Application of PI3K inhibitors, wortmannin and LY294002 attenuated the depression of TNF-alpha and iNOS expression by amlodipine in LPS-induced cardiomyocytes. These findings may explain some cardioprotective effects of amlodipine in LPS-mediated sepsis and suggest that the inhibition of TNF-alpha and iNOS expression by amlodipine is, at least in part, dependent on PI3K/Akt signaling pathway.

Antivirus and immune enhancement activities of sulfated polysaccharide from Angelica sinensis.

This study is to synthesize sulfated Angelica polysaccharides (APSs) and investigate the activity of one of the sulfated derivatives APS-1 on murine leukemia virus in vivo. Six sulfated derivatives with degree of sulfation ranging from 0.68 to 1.91 were obtained. And the virus replication was inhibited by APS-1 at the dose of 10 and 30 mg/kg (26% and 30% inhibition respectively). Furthermore, both the percentage of CD4(+) cells and CD4(+)/CD8(+) ratio in peripheral blood cells were significantly enhanced by APS-1 at 3-30 mg/kg. In addition, the reduced thymus/body weight index by murine leukemia virus infection was increased by ASP-1 in a dose dependent manner. These results suggest that APS-1 could not only inhibit virus replication, but also improve the immune function. APS-1 may be a potential new and better antiviral drug.

The beneficial effect of Rheum tanguticum polysaccharide on protecting against diarrhea, colonic inflammation and ulceration in rats with TNBS-induced colitis: The role of macrophage mannose receptor in inflammation and immune response

Rhubarb has been used as a folk remedy for gastrointestinal disease in China for over two thousand years. In the present study, we evaluated the effect of Rheum tanguticum polysaccharide (RTP), a water soluble fraction extracted from rhubarb, on protection from inflammation and colonic damage in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats. RTP protected against diarrhea, colon weight increase, and ulceration induced by TNBS. It was at least as effective as dexamethasone (DEX). RTP significantly decreased myeloperoxidase (MPO) activity in the colonic mucosa. Oral administration of RTP was as effective as intraperitoneal (i.p.) injection on toxicity protection and MPO activity. To further investigate the possible underlying mechanism, we studied the role of mannose receptor (MR) in cytokine secretion, ligand binding and endocytosis of macrophages. The secretion of IFN-gamma was dramatically increased while IL-4 decreased in colitis compared to the control (normal rats), and RTP restored the condition similar to the control in vivo. The secretion of IFN-gamma by macrophages was induced by RTP and lipoarabinomannan (LAM) but not mannose in vitro. Mannose completely inhibited the effect of RTP, while RTP and LAM affected each other on IFN-gamma secretion. The MR-mediated ligand binding and endocytosis of macrophages were markedly decreased in colitis and RTP restored their function to near normal condition. The results indicated that RTP targeted MR and down-regulation of Th1-polarized immune response may be the possible mechanism for its attenuation of intestinal inflammation and damage. RTP may be useful for treatment of patients with inflammatory bowel disease.

Immunomodulation of Rheum tanguticum polysaccharide (RTP) on the immunosuppressive effects of dexamethasone (DEX) on the treatment of colitis in rats induced by 2,4,6-trinitrobenzene sulfonic acid

Dexamethasone (DEX) is still the main choice for colitis, although the immunosuppressive side effects are still the troublesome problems to overcome. In our previous study, Rheum tanguticum polysaccharide (RTP), extracted from traditional Chinese medicine rhubarb, targeted mannose receptor, showed immunoregulatory effect on the balance of Th1 and Th2 polarization in colitis rats. For the present study, we hypothesized that RTP could regulate the immunosuppressive effects of DEX. Taking advantage of the colon delivery ability of the polysaccharide, we prepared the double emulsion of RTP microsphere containing DEX to investigate the potential immunoregulatory effects of RTP on DEX immunosuppression in TNBS-induced colitis in rats. As expected, DEX-RTP microsphere showed not only significant immunomodulatory effects, but also strong anti-inflammation. The microsphere balanced enteric bacteria disorder, decreased TLR4 activation and promoted the balance of Th1 and Th2 polarization, inhibited NF-kappaB activity. Especially, DEX-RTP showed significant colon injury reparation. DEX alone exhibited a strong anti-inflammatory effect by suppressing MPO activity, down-regulate NF-kappaB activity and Th1 cytokines production. However, DEX showed severe immunosuppressive effects. It aggravated the intestinal commensal bacteria disorder, induced thymus atrophy and the further imbalance of Th1/Th1 cytokine polarization. RTP showed significant immunoregulatory effects. A significant protection on the intestinal bacterial balance, TLR4 and NF-kappaB activation decreased, and Th1/Th2 cytokine production balance were showed in RTP. In conclusion, DEX-RTP microsphere delivered DEX directly to the colon avoiding the absorption at the upper intestinal tract and showed synergistic effects on colitis both from the strong anti-inflammatory effects of DEX and from the immunoregulation of RTP.

In Vitro and In Vivo Antitumor Activity of a Novel pH-Activated Polymeric Drug Delivery System for Doxorubicin

Background Conventional chemotherapy agent such as doxorubicin (DOX) is of limited clinical use because of its inherently low selectivity, which can lead to systemic toxicity in normal healthy tissue. Methods A pH stimuli-sensitive conjugate based on polyethylene glycol (PEG) with covalently attachment doxorubicin via hydrazone bond (PEG-hyd-DOX) was prepared for tumor targeting delivery system. While PEG-DOX conjugates via amid bond (PEG-ami-DOX) was synthesized as control. Results The synthetic conjugates were confirmed by proton nuclear magnetic resonance (NMR) spectroscopy, the release profile of DOX from PEG-hyd-DOX was acid-liable for the hydrazone linkage between DOX and PEG, led to different intracellular uptake route; intracellular accumulation of PEG-hyd-DOX was higher than PEG-ami-DOX due to its pH-triggered profile, and thereby more cytotoxicity against MCF-7, MDA-MB-231 (breast cancer models) and HepG2 (hepatocellular carcinoma model) cell lines. Following the in vitro results, we xenografted MDA-MB-231 cell onto SCID mice, PEG-hyd-DOX showed stronger antitumor efficacy than free DOX and was tumor-targeting. Conclusions Results from these in vivo experiments were consistent with our in vitro results; suggested this pH-triggered PEG-hyd-DOX conjugate could target DOX to tumor tissues and release free drugs by acidic tumor environment, which would be potent in antitumor drug delivery.

A new natural angelica polysaccharide based colon‐specific drug delivery system

Colon-specific drug delivery systems are clinically necessary to treat colon diseases locally while minimizing systemic side effects. In this study, we extracted angelica polysaccharide from fresh roots of Angelica sinensis Diels and analyzed the monosaccharide components. With succinate as a cross-linker and angelica polysaccharide as a drug carrier, a dexamethasone-polysaccharide conjugate was synthesized. The amount of dexamethasone (Dex) loaded in the dexamethasone-polysaccharide conjugate was 14.13/100 mg. The newly synthesized dexamethasone-polysaccharide conjugate was found to greatly reduce systemic absorption of Dex and effectively deliver Dex to the large intestine. When dexamethasone-polysaccharide conjugate was used to treat TNBS-induced ulcerative colitis in rats by gavage, the ulcerative area of the colon and the colonic myeloperoxidase (MPO) activity was reduced in a dose-dependent manner. There was no effects on spleen weight, thymus weight, or peripheral blood lymphocyte count (0.25 micromol kg(-1) day(-1)). These results indicate that the dexamethasone-polysaccharide conjugate has a therapeutic effect on TNBS-induced ulcerative colitis in rats, while simultaneously reducing the systemic immunosuppression caused by Dex. Thus, the angelica polysaccharide was a promising colon-specific drug carrier, and the new dexamethasone-polysaccharide conjugate may yield a potential drug for the treatment of human inflammatory bowel disease.

In Vivo Anti-Tumor Activity of a New Doxorubicin Conjugate via α-Linolenic Acid

The conventional chemotherapy agent, doxorubicin, is of limited clinical use because of its systemic toxicity toward normal healthy tissue. A new doxorubicin conjugate with α-linolenic acid showed good anti-tumor activity with lower toxicity than free doxorubicin and exhibited an active tumor-targeting profile due to the introduction of α-linolenic acid which might be an effective tumor-targeting moiety for the modification of chemotherapeutics.