Reactive nitrogen species modulate the effects of rhein, an active component of senna laxatives, on human epithelium in vitro

The Metabolism and Pharmacokinetics of Rhein and Aurantio-Obtusin

BACKGROUND

Anthraquinones, rhein and aurantio-obtusin were isolated from the herb Duhaldea nervosa for the first time by our group, which were also found in plants that belong to the plant family Compositae. Anthraquinone compounds have a range of pharmacological activities such as anti-inflammatory, anti-cancer, antioxidation, anti-diabetes, etc. and can be used as a laxative, for liver protection, treatment of chronic renal failure, etc. However, in recent years, anthraquinones have been reported to be cytotoxic to the liver and kidneys. Therefore, it is very important to study the pharmacokinetics and metabolism of rhein and aurantio-obtusin, which are common ingredients in many traditional Chinese medicines (TCM). According to our research, the pharmacokinetics and metabolism of rhein and aurantio-obtusin are comprehensively summarized in the paper for the first time.

OBJECTIVE

The study provides comprehensive information on pharmacokinetics and metabolism of rhein and aurantio- obtusin in different Species; meanwhile, the aim of this review is also to provide a reference for a reasonable application of TCM enriched with these two ingredients.

METHODS

The metabolism and pharmacokinetics of rhein and aurantio-obtusin were searched by the Web of Science, PubMed, Google scholar and some Chinese literature databases.

RESULTS

Rhein and aurantio-obtusin exist mainly in the form of metabolites in the body. Rhein and aurantio-obtusin and its metabolites might be responsible for pharmacological effects in the body. Therefore, the significance of studying the in vivo metabolites of rhein and aurantio-obtusin is not only essential to clarify their pharmacological mechanism, but also to find new active compound ingredients. The metabolism of rhein is different in different species, so the toxicity effects of rhein may also be different after oral administration in different species; however, the metabolic profiles of aurantio-obtusin in the liver microsomes of different species are similar.

CONCLUSION

This paper not only provides detail regarding the pharmacokinetics of rhein and aurantio-obtusin, but it is anticipated that it will also facilitate further study on the metabolism of rhein and aurantio-obtusin.

Are Senna based laxatives safe when used as long term treatment for constipation in children?

BACKGROUND AND AIM

Senna is a stimulant laxative commonly used by pediatricians, pediatric gastroenterologists, and pediatric surgeons. Many clinicians avoid Senna for reasons such as tolerance or side effects but this has little scientific justification. We recently found several patients we were caring for developed perineal blistering during the course of Senna treatment. Because of this we chose to review the literature to identify side effects in children taking this medication as well as to analyze our Center's experience with Senna's secondary effects.

METHODS

We performed a literature review (MEDLINE, PUBMED) using the keywords of Senna, sen, sennosides and children, and pediatric and functional (idiopathic) constipation. We looked for articles with information regarding perineal blisters related to Senna as well as other secondary effects of Senna laxatives in children when used on a long-term basis. We also reviewed the charts of our patients who had previously taken Senna or are currently taking Senna, looking for adverse reactions.

RESULTS

Eight articles in the literature reported perineal blisters after administration of Senna laxatives in 28 patients. Of those occurrences, 18 patients (64%) had accidental administration of Senna and 10 (36%) had Senna prescribed as a long term treatment. All of the blistering episodes were related to high dose, night-time accidents, or intense diarrhea with a long period of stool to skin contact. At our institution, from 2014 to 2017, we prescribed Senna and have recorded data to 640 patients. During the study period, 17 patients (2.2%) developed blisters during their treatment. Patients who developed blisters had higher doses 60mg/day; 60 [12-100] vs. 17.5 [1.7-150] (p<0.001). All of the blistering episodes were related to night-time accidents, with a long period of stool to skin contact. 83 (13%) patients presented minor side effects such as abdominal cramping, vomiting or diarrhea which resolved once the type of laxatives were changed or enemas were started. The doses of Senna was not significantly different in these patients 15mg/day [4.4-150] vs. 17.5mg/day [1.5-150]. There were no other long-term side effects from Senna found in the pediatric literature for long-term treatment besides abdominal cramping or diarrhea during the first weeks of administration. We found no evidence of tolerance to Senna in our review.

CONCLUSION

There is a paucity of information in the literature regarding side effects of sennosides as a long-term therapy, and to our knowledge, this is the first review of Senna side effects in children. Senna induced dermatitis is rare, but may occur when patients need a higher dose. All of the cases described had a long period of exposure of the skin to stool. Besides the perineal rash with blisters, we could find no other described major side effect with Senna administration in the pediatric population or evidence of the frequently mentioned concern of the development of tolerance to Senna. Pediatric caregivers should advise families of the rare side effect of skin blistering and educate them to change the diaper frequently in children who are not toilet- trained to reduce stool to skin exposure. We can conclude from this review that Senna is a safe treatment option for constipation in children.

LEVEL OF EVIDENCE

IV.

Rhein: A Review of Pharmacological Activities

Rhein (4, 5-dihydroxyanthraquinone-2-carboxylic acid) is a lipophilic anthraquinone extensively found in medicinal herbs, such as Rheum palmatum L., Cassia tora L., Polygonum multiflorum Thunb., and Aloe barbadensis Miller, which have been used medicinally in China for more than 1,000 years. Its biological activities related to human health are being explored actively. Emerging evidence suggests that rhein has many pharmacological effects, including hepatoprotective, nephroprotective, anti-inflammatory, antioxidant, anticancer, and antimicrobial activities. The present review provides a comprehensive summary and analysis of the pharmacological properties of rhein, supporting the potential uses of rhein as a medicinal agent.

Rhein inhibits lipopolysaccharide-induced intestinal injury during sepsis by blocking the toll-like receptor 4 nuclear factor-κB pathway

Sepsis is one of the leading causes of mortality in severe systemic inflammatory syndrome. The endotoxin-induced inflammatory response has been linked to the development of sepsis. Rhein is a lipophilic anthraquinone isolated from Rheum rhabarbarum (rhubarb), which has a protective effect on intestinal damage in vivo. However, the underlying mechanism responsible for the protective effects of rhein remains to be elucidated. In the present study, mice were exposed to 20 mg/kg lipopolysaccharide (LPS), prior to being treated with either 100 mg/kg rhein or 0.3 mg/kg toll‑like receptor 4 (TLR4) signaling inhibitor TAK‑242. In the rhein‑treated mice, the colon length (cm) was extended and colon injury was attenuated. In addition, treatment with rhein significantly decreased the expression levels of the LPS‑induced inflammatory cytokines interleukin (IL)‑1β, IL‑6, IL‑8, and tumor necrosis factor‑α, in both the plasma and colon tissue. However, mice treated with TAK‑242 exhibited increased expression levels of IL‑10, as determined by ELISA and western blot analysis. In addition, immunohistochemistry and western blot analyses demonstrated that treatment with rhein was able to reduce TLR4 expression and inhibit nuclear factor‑κB (NF‑κB) phosphorylation in colon tissue. Furthermore, LPS induction was blocked by TAK‑242. These results demonstrate that the observed rhein‑attenuated inflammatory response during sepsis may be achieved via the TLR4 NF‑κB signaling pathway. In conclusion, the results of the present study provide a novel insight into the protective effects of rhein on LPS‑induced intestinal inflammation, and demonstrate that rhein may act as a beneficial therapeutic agent in the treatment of sepsis-induced intestinal damage.

Synthesis and antitumor activities of novel rhein α-aminophosphonates conjugates

Several rhein α-aminophosphonates conjugates (5a-5q) were synthesized and evaluated for in vitro cytotoxicity against HepG-2, CNE, Spca-2, Hela and Hct-116 cell lines. Some compounds showed relatively high cytotoxicity. Especially, compound 5i exhibited the strongest cytotoxicity against Hct-116 cells (IC50 was 5.32 μM). All the synthesized compounds exhibited low cytotoxicity against HUVEC cells. The mechanism of compound 5i was preliminarily investigated by Hoechst 33258 staining, JC-1 mitochondrial membrane potential staining and flow cytometry, which indicated that the compound 5i induced apoptosis in Hct-116 cancer cells. Cell cycle analysis showed that these compound 5i mainly arrested Hct-116 cells in G1 stage. The effects of 5i on the activation of caspases expression indicated that 5i might induce apoptosis via the membrane death receptor pathways. In addition, the binding properties of a model analog 5i to DNA were investigated by methods (UV-vis, fluorescence, CD spectroscopy and FRET-melting) in compare with that of rhein. Results indicated that 5i showed moderate ability to interact ct-DNA.

Synthesis, cytotoxicity, DNA binding and apoptosis of rhein-phosphonate derivatives as antitumor agents

Several rhein-phosphonate derivatives (5a-c) were synthesized and evaluated for in vitro cytotoxicity against HepG-2, CNE, Spca-2, Hela and Hct-116 cell lines. Some compounds showed relatively high cytotoxicity. Especially compounds 5b exhibited the strongest cytotoxicity against HepG-2 and Spca-2 cells (IC50 was 8.82 and 9.01 µM), respectively. All the synthesized compounds exhibited low cytotoxicity against HUVEC cells. Further experiments proved that 5b could disturb the cell cycle in HepG-2 cells and induce apoptosis. In addition, the binding properties of a model conjugate 5b to DNA were investigated by methods (UV-Vis, fluorescence, CD spectroscopy). Results indicated that 5b showed moderate ability to interact ct-DNA.

An evidence-based systematic review of senna (Cassia senna) by the Natural Standard Research Collaboration

An evidence-based systematic review, including written and statistical analysis of scientific literature, expert opinion, folkloric precedent, history, pharmacology, kinetics/dynamics, interactions, adverse effects, toxicology, and dosing.

Emodin and rhein inhibit LIGHT-induced monocytes migration by blocking of ROS production

LIGHT is known to act as a novel mediator for atherogenesis. Furthermore, it has been reported that emodin, an active component extracted from rhubarb, can stop the growth of cancer cells. However, it is not known if emodin exerts anti-atherogenic effects in the human monocyte, THP-1, following treatment with LIGHT. In this study, we evaluated the inhibitory effect of emodin and rhein on LIGHT-induced migration in THP-1. Emodin and rhein decreased the level of LIGHT-induced generation of ROS, as well as the expression of CCR1, CCR2 and ICAM-1 and the production of IL-8, MCP-1, TNF-alpha, and IL-6. Emodin and rhein also decreased the phosphorylation of the p38 MAPK and IkB-alpha. Furthermore, the NADPH oxidase assembly inhibitor, AEBSF, and the blocker of NADPH oxidase, p47(phox) small interference RNA (siRNA), also efficiently blocked LIGHT-induced migration, CCR1, CCR2, ICAM-1, and HVEM expression, and p38 MAPK and NF-kB activation. These findings indicate that the inhibitory effects of emodin and rhein on LIGHT-induced migration occur via decreasing ROS production and NADPH oxidase p47(phox) activation. Taken together, these results indicate that emodin and rhein have the potential for use as an anti-atherosclerosis agent.

Maturation of gastric electrical activity, gastric emptying and intestinal permeability in preterm newborns during the first month of life

INTRODUCTION

Immaturity of motility, intestinal epithelial barrier function and absorptive capacity may play a role in the pathophysiology of intestinal diseases in preterms. We determined the gastric electrical activity and emptying, and intestinal permeability, in preterm newborns to verify if a maturation pattern exists in preterm newborns during the first month of life.

PATIENTS AND METHODS

Eighteen preterm newborns (median 34 wks, range 2 wks) completed the study. They underwent the recording of gastric electrical activity by means of cutaneous electrogastrography, the ultrasound examination of gastric emptying, and the lactulose-to-mannitol ratio from permeability-absorption test on days 3, 7, 15, and 30 after birth.

RESULTS

Gastric electrical activity and emptying showed only slight changes between day 3 and day 7. On the contrary, an evident maturation in permeability, expressed as L/Mratio, was evident over time (Friedman Repeated Measures Analysis, p = 0.004).

CONCLUSION

In preterm healthy newborns of 34 weeks gestational age, electrical and motor activity are completely developed at birth whilst the intestinal epithelial barrier clearly improves during the first week of life.

Rhein inhibits invasion and migration of human nasopharyngeal carcinoma cells in vitro by down-regulation of matrix metalloproteinases-9 and vascular endothelial growth factor

Progression of cancer invasion is believed to be dependent on the remodeling of extracellular matrix induced by tumor cells. Rhein has been shown to inhibit the growth and proliferation of human nasopharyngeal carcinoma (NPC) cells. However, the molecular mechanism underlying rhein-induced inhibition of cancer invasion has not been explored. Herein, we show that rhein could inhibit the invasion and migration of NPC cells in vitro. Rhein inhibits invasion by reducing the expression of matrix metalloproteinase-9 (MMP-9) and vascular endothelial growth factor (VEGF). Moreover, we demonstrate that the pathway involved in rhein-inhibited invasion is presumably through the growth factor receptor bound protein 2/son of sevenless-Ras-mitogen-activated protein kinase (GRB2/SOS-Ras-MAPK) pathway, as shown by an decrease in the expression levels of GRB2, SOS-1 and Ras as well as led to suppression of the phosphorylation of extracellular signal-regulated kinase (ERK) and p38 MAPK. Further study has shown that rhein also inhibited activation of transcription factor nuclear factor kappaB (NF-kappaB), which is known to implicate the regulation of MMP-9 and VEGF gene expression in cancer invasion. Our findings suggest that rhein inhibits the invasion of NPC cells may be mediated in part through the suppression of MMP-9 and VEGF expression via the modulation of NF-kappaB signaling pathway.

Transport of sennosides and sennidines from Cassia angustifolia and Cassia senna across Caco-2 monolayers--an in vitro model for intestinal absorption

Laxative effects of Senna preparations are mainly mediated by rheinanthrone, a metabolite formed in the intestinal flora from dianthrones. Nevertheless, it was not clear whether dianthrones are bioavailable at all and contribute to the overall effects of this important medicinal plant. Using the Caco-2 human colonic cell line as an in vitro model of the human intestinal mucosal barrier, the bioavailability of dianthrones was studied in apical to basolateral (absorptive) and basolateral to apical (secretive) direction. Permeability coefficients (P(c)) and percent transport were calculated based on quantitations by HPLC. From the data obtained it was concluded that sennosides A and B, as well as their aglycones sennidine A and B are transported through the Caco-2 monolayers in a concentration-dependent manner and their transport was linear with time. The absorption in apical to basolateral direction was poor and P(c) values were comparable to mannitol. The transport was higher in the secretory direction, indicating a significant efflux (e.g. by efflux pumps) of the (poorly) absorbed compounds in the intestinal lumen again. Our findings support the general understanding that the laxative effects of Senna are explainable mainly by metabolites and not by the natively present dianthrones.

Bile acids modulate tight junction structure and barrier function of Caco-2 monolayers via EGFR activation

Intestinal and systemic illnesses have been linked to increased gut permeability. Bile acids, whose luminal profile can be altered in human disease, modulate intestinal paracellular permeability. We investigated the mechanism by which selected bile acids increase gut permeability using a validated in vitro model. Human intestinal Caco-2 cells were grown in monolayers and challenged with a panel of bile acids. Transepithelial electrical resistance and luminal-to-basolateral fluxes of 10-kDa Cascade blue-conjugated dextran were used to monitor paracellular permeability. Immunoprecipitation and immunoblot analyses were employed to investigate the intracellular pathway. Redistribution of tight junction proteins was studied by confocal laser microscopy. Micromolar concentrations of cholic acid, deoxycholic acid (DCA), and chenodeoxycholic acid (CDCA) but not ursodeoxycholic acid decreased transepithelial electrical resistance and increased dextran flux in a reversible fashion. Coincubation of 50 muM CDCA or DCA with EGF, anti-EGF monoclonal antibody, or specific src inhibitor 4-Amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP-2) abolished the effect. A concentration of 50 muM of either CDCA or DCA also induced EGF receptor phosphorylation, occludin dephosphorylation, and occludin redistribution at the tight junction level in the same time frame and in a reversible fashion. We conclude that selected bile acids modulate intestinal permeability via EGF receptor autophosphorylation, occludin dephosphorylation, and rearrangement at the tight junction level. The effect is mediated by the src family kinases and is abolished by EGF treatment. These data also support the role of bile acids in the genesis of necrotizing enterocolitis and the protective effect of EGF treatment.

Effect of hyperbilirubinemia on intestinal permeability in healthy term newborns

We investigated the effect of serum bilirubin (SB) on intestinal permeability (IP) of healthy, term, birth weight appropriate for gestational age neonates before phototherapy. IP was measured by the dual probe (lactulose/mannitol) sugar absorption test (SAT) performed on the third day of life in 12 healthy jaundiced newborns (total bilirubin 249 +/- 39.75 micromol/L) and compared to that of 12 non-jaundiced newborns (total bilirubin 83.79 + 37.62 micromol/L) matched for sex, gestational age, birth weight and Apgar score. Jaundiced newborns have a significantly higher La/Ma ratio than non-jaundiced (0.31 +/- 0.28 vs. 0.053 +/- 0.043; p < 0.0004). A significant correlation was found between serum bilirubin level and La/Ma ratio (r = 0.56 p < 0.006).

CONCLUSION

Our study demonstrates a direct effect of UCB on gut epithelial barrier of at-term newborns in whom UCB appears to be responsible for an alteration of IP that theoretically may lead to a passage of macromolecules through the intestinal epithelium increasing the risk of sensitization.

Unconjugated bilirubin modulates the intestinal epithelial barrier function in a human-derived in vitro model

Unconjugated bilirubin promotes intestinal secretion without affecting nutrient digestion or absorption. In the current study, the effects of unconjugated bilirubin (UCB) on the barrier function of the intestinal epithelium were investigated. The apical side of human intestinal cell line Caco-2 monolayers was challenged with purified UCB. Transepithelial electrical resistance and paracellular fluxes of 10 kD Cascade blue conjugate dextran were measured. Cell monolayer viability was studied using LDH release and trypan blue exclusion tests. Redistribution of enterocyte tight junction occludin was studied by confocal microscopy. Bilirubin induced a dose-dependent decrease of transepithelial electrical resistance (TEER). This effect was maximal at 6 h and tended to be reversed at 48 h. Oxidated bilirubin was ineffective. Bilirubin significantly increased fluorescent dextran paracellular passage. Cell viability was not affected by UCB over the 5-200 nmol/L concentration range. Finally, bilirubin triggered a reversible redistribution of tight junctional occludin. UCB increases the permeability of intestinal epithelium. This effect is reversible, dependent on the redox status of the molecule and the rearrangement of the tight junction. These data attribute to bilirubin a novel role of functional modulator of intestinal paracellular permeability in vitro.

Effect of Ethanol Extracts of Three Chinese Medicinal Plants with Laxative Properties on Ion Transport of the Rat Intestinal Epithelia

The effects of ethanol extracts of three Chinese medicinal plants Dahuang (Rheum palmatum L.), Badou (Croton tiglium L.), and Huomaren (Cannabis sativa L.), on ion transport of the rat intestinal epithelia were studied. Rat intestinal epithelia mounted in an Ussing chamber attached with voltage/current clamp were used for measuring changes of the short-circuit current across the epithelia. The intestinal epithelia were activated with current raised by serosal administration of forskolin 5 microM. Ethanol extracts of the three plants all augmented the current additively when each was added after forskolin. In subsequent experiments, ouabain and bumetanide were added prior to ethanol extracts of these medicinal plants to determine their effect on Na(+) and Cl(-) movement. The results suggest that ethanol extracts of the three medicinal plants may affect the Cl(-) movement more directly than Na(+) movement in the intestinal epithelial cells. The results provide evidence for the pharmacologic mechanism of the three Chinese medicinal plants on the intestinal tract.

Rhein induces apoptosis in HL-60 cells via reactive oxygen species-independent mitochondrial death pathway

Rhein is an anthraquinone compound enriched in the rhizome of rhubarb, a traditional Chinese medicine herb showing anti-tumor promotion function. In this study, we first reported that rhein could induce apoptosis in human promyelocytic leukemia cells (HL-60), characterized by caspase activation, poly(ADP)ribose polymerase (PARP) cleavage, and DNA fragmentation. The efficacious induction of apoptosis was observed at 100 microM for 6h. Mechanistic analysis demonstrated that rhein induced the loss of mitochondrial membrane potential (DeltaPsi(m)), cytochrome c release from mitochondrion to cytosol, and cleavage of Bid protein. Rhein also induced generation of reactive oxygen species (ROS) and the phosphorylation of c-Jun N-terminal kinase (JNK) and p38 kinase. However, these actions seem not to be associated with the apoptosis induction because antioxidants including N-acetyl cysteine (NAC), Tiron, and catalase did not block rhein-induced apoptosis, although they could block the generation of ROS and the phosphorylation of JNK and p38 kinase. Our data demonstrate that rhein induces apoptosis in HL-60 cells via a ROS-independent mitochondrial death pathway.