Liujunanwei decoction attenuates cisplatin-induced nausea and vomiting in a Rat-Pica model partially mediated by modulating the gut micsrobiome.

Studies show that traditional Chinese medicine (TCM), such as Liujunanwei (LJAW) decoction, can play important roles in alleviating side effects of chemotherapy. The purpose of this study was to understand how LJAW can counter chemotherapy-induced emesis via alteration of gut microbiota. We evaluated the effect of LJAW on cisplatin (DDP)-induced nausea and vomiting using a rat-pica model. Rats react to emetic-producing stimuli with increased kaolin consumption, a phenomenon called pica. The rats were injected with cisplatin and then randomly assigned to the control (DDP), Ondansetron or LJAW. The intake of kaolin and chow diet as well as body weights were recorded every 24 hours. Fecal samples were collected prior to, after three and seven days of treatment. The expression of proteins was measured by western blot. The concentration of cytokines and serotonin was evaluated using ELISA assay kits. Kaolin consumption in rats induced by cisplatin was reduced by 16.5%, 22.5%, and 30.1% in the LJAW group compared to the DDP group at 24 hours, 48 hours and 72 hours, respectively (p>0.05). LJAW significantly increased the food intake of the rats (13.94 ± 4.73 g) during the first 24 hours as opposed to the DDP (9.23 ± 3.77 g) (p<0.05). 16S rRNA gene sequencing showed the abundance of Bacteroidetes increased in cisplatin treated rats. In addition, cisplatin injection caused an enrichment of Escherichia-Shigella and Enterococcus at the genus level. While, enrichment of Blautia and Lactobacillus was presented in LJAW treated rats. Serotonin decreased in LJAW treated intestine and medulla oblongata tissues. Further, the protein expression of tryptophan hydroxylase 1 (TPH1) a rate limiting enzyme of serotonin was inhibited in LJAW treated rat's jejunum compared with cisplatin only treated rats. In addition, LJAW downregulated chemotherapy induced elevated inflammation. The results of this study indicated that LJAW is capable of decreasing cisplatin-induced kaolin intake in rat-nausea model (pica), which might be mediated through gut microbiome-induced anti-inflammation and anti-serotonin synthesis functions.

Effects of Rikkunshi-To, a Japanese kampo medicine, on donepezil-induced gastrointestinal side effects in mice.

Donepezil, an acetylcholinesterase inhibitor, is associated with gastrointestinal symptoms, such as nausea, vomiting, and anorexia, which may affect adherence to continuous therapy. Since Rikkunshi-To, a Japanese herbal medicine, activates the ghrelin signaling pathway and promotes gastrointestinal function, it is administered to prevent gastrointestinal symptoms. We herein investigated whether donepezil-induced gastrointestinal side effects in mice are ameliorated by Rikkunshi-To and if its therapeutic efficacy is mediated by ghrelin. Since pica behavior, the ingestion of kaolin, correlates with nausea and vomiting in humans, donepezil was intraperitoneally administered with or without Rikkunshi-To daily to mice, and food and kaolin intakes were monitored. The effects of donepezil on intestinal motility and a ghrelin receptor antagonist on donepezil-induced pica behavior, anorexia, and changes in intestinal motility were examined in mice treated with Rikkunshi-To. Pica behavior and anorexia were significantly induced by donepezil and significantly inhibited by Rikkunshi-To. Intestinal motility was significantly suppressed by donepezil and promoted by Rikkunshi-To. Furthermore, the therapeutic effects of Rikkunshi-To were antagonized by the ghrelin receptor antagonist. The present results support the therapeutic efficacy of Rikkunshi-To against donepezil-induced gastrointestinal side effects.

Effect of niacin supplementation on nausea-like behaviour in an isoniazid-induced mouse model of pellagra.

Niacin deficiency causes pellagra, the symptoms of which include dermatitis, diarrhoea and dementia. Investigating the mechanism underlying these phenotypes has been challenging due to the lack of an appropriate animal model. Here, we report a mouse model of pellagra-related nausea induced by feeding mice a low-niacin diet and administering isoniazid (INH), which is thought to induce pellagra. Mice fed a normal or low-niacin diet received INH (0·3 or 1·0 mg/mg per animal, twice daily, 5 d), and nausea was evaluated based on pica behaviour, which considered the rodent equivalent of the emetic reflex. Furthermore, the effect of therapeutic niacin administration on nausea was evaluated in this model. Urinary and hepatic metabolite levels were analysed by LC coupled with MS. INH-induced pica was observed in mice fed a low-niacin diet but not in those fed a normal diet. Levels of urinary metabolites, such as 1-methyl-2-pyridone-5-carboxamide, kynurenic acid and xanthurenic acid, were significantly reduced in the mice treated with INH compared with those that did not receive INH. Furthermore, niacin supplementation prevented pica and restored the levels of some metabolites in this mouse model. Our findings suggest that INH-related nausea is pellagra-like. We also believe that our newly established method for quantifying pica is a useful tool for investigating the mechanisms of pellagra-related nausea.

Forsythiae Fructus aqueous extract attenuates cisplatin-induced kaolin consumption (pica) by inhibiting NLRP3 inflammasome activation in rats.

The present study was conducted to evaluate the effect of Forsythiae Fructus aqueous extract (FAE) against cisplatin-induced emesis and to explore the antiemetic mechanism of FAE by focusing on NLRP3 inflammasome activation in a rat pica model. Our results showed that FAE significantly ameliorated cisplatin-induced acute and delayed pica in rats. Moreover, FAE improved the gastrointestinal histopathological injury and reduced the levels of serum ROS, IL-1ß, and IL-18 in cisplatin-treated rats. In addition, the expressions of NLRP3, ASC, caspase-1, and IL-1ß and the colocalization of the NLRP3 with ASC or caspase-1 in rat gastric antrum and ileum were also suppressed by FAE. Taken together, our findings indicate that FAE has a therapeutic effect against CINV, which may be related to its inhibition of the activation of NLRP3 inflammasome.

RNA-Seq reveals inflammatory mechanisms of Xiao-Ban-Xia-Tang decoction to ameliorate cisplatin-induced emesis in a rat pica model.

OBJECTIVES: Xiao-Ban-Xia-Tang decoction (XBXT), an antiemetic formula in traditional Chinese medicine, has been proved to be a potential treatment for chemotherapy-induced nausea and vomiting (CINV), but the underlying mechanisms are not adequately understood. This study aimed to investigate changes in the ileum transcriptome after cisplatin and XBXT treatment and to reveal whether the antiemetic mechanisms of XBXT are related to its anti-inflammatory effect. METHODS: The pica model was established by a single intraperitoneal injection of 6 mg/kg cisplatin in Wistar rats. Tissues from the gastric antrum and ileum were stained with hematoxylin-eosin to observe gastrointestinal tract pathological changes. Based on the differentially expressed genes (DEGs) which were altered by cisplatin and reversed by XBXT, the transcriptome data of rat ileum were analyzed by GO, KEGG, and PPI analyses. Several inflammatory DEGs were validated by RT-PCR. RESULTS: XBXT could reduce kaolin intake up to 72 h after modeling and alleviate the inflammatory damage of gastric antrum and ileum induced by cisplatin. According to the transcriptome profile, there were 75 DEGs down-regulated by cisplatin and up-regulated by XBXT and 343 DEGs up-regulated by cisplatin and down-regulated by XBXT. XBXT could blunt the overexpression of tryptophan hydroxylase 1 (the rate-limiting enzyme of serotonin synthesis) in ileum. Enrichment analysis showed that inhibiting overexpression of several conventional inflammation pathways and pro-inflammation cytokines were related to the antiemetic effectiveness of XBXT. CONCLUSIONS: This study implies that inhibiting inflammatory signaling pathways and synthesis of serotonin might be potential mechanisms of XBXT's antiemetic effect against CINV.

Enhancement of ghrelin-signaling system by Rikkunshi-To attenuates teriparatide-induced pica in rats.

Teriparatide is clinically used for the treatment of osteoporosis; however, nausea is often observed in patients. Its insufficient control affects the ability to continue teriparatide therapy. Rikkunshi-To (RKT), a traditional Japanese herbal medicine, improves the gastrointestinal function via activation of the ghrelin-signaling system. We investigated the therapeutic effects of RKT on teriparatide-induced nausea in rats and the involvement of ghrelin in these effects. We previously reported that ovariectomized rats showed pica (kaolin ingestion), a behavior that can be used to assess nausea in rats, after the subcutaneous administration of teriparatide; thus, the behavior was used as an index of nausea. Ovariectomized rats were fed diets with or without RKT (1%) for 2 weeks, and then they received the subcutaneous injection of teriparatide (400 µg/kg). Teriparatide significantly increased the incidence of pica, while suppressing intestinal motility and plasma ghrelin levels in rats fed normal diets; however, rats fed diets with RKT showed improvements in all of the teriparatide-induced adverse reactions. These therapeutic effects were antagonized by a ghrelin receptor antagonist ([D-Lys3]-GHRP-6; 200 nmol/rat). These findings suggest that the enhancement of ghrelin-signaling is involved in RKT's therapeutic effect, and that RKT is a potentially useful treatment for teriparatide-induced nausea.

Strain differences in the development of cisplatin-induced pica behavior in mice.

INTRODUCTION: Pica behavior, kaolin ingestion, in rats and mice can be used as an assessment of nausea and vomiting; however, we observed that the incidence of pica behavior in ICR strain mice varied markedly. We investigated the susceptibility of four strains of mice (ICR, BALB/c, C57BL/6, and DBA/2) to the development of pica behavior. METHODS: Mice received cisplatin (7.5 mg/kg, i.p.) with or without a serotonin 5-HT3 receptor antagonist (granisetron: 0.1 mg/kg, i.p.) or tachykinin NK1 receptor antagonist (fosaprepitant: 30 mg/kg, i.p.), and then their daily kaolin intake was measured for 2 days. We examined the expression of preprotachykinin (PPT)-A mRNA in the medulla of cisplatin-treated mice 8 and 32 h after drug administration. RESULTS: All mice except for ICR strain significantly increased kaolin intake after cisplatin administration. Among the tested strains, DBA/2 mice compared to BALB/c and C57BL/6 mice notably showed pica behavior on both days (P < 0.0001). The expression of PPT-A mRNA was significantly increased 8 h after cisplatin administration in all strains, but the increase remained on the second day only in DBA/2 mice (P < 0.05). Granisetron significantly inhibited pica behavior in DBA/2 mice on the first day (P < 0.0001), but not the second day; however, fosaprepitant completely inhibited the pica behavior on both days (P < 0.001). DISCUSSION: These results indicate that cisplatin-induced pica behavior in mice is likely to be influenced by the genotype, and that DBA/2 mice are useful to analyze the emetogenic or anti-emetic potential of drugs in preclinical studies.

Saponin and non-saponin fractions of red ginseng ameliorate cisplatin-induced pica in rats.

CONTEXT: Nausea and vomiting are considered as the foremost unpleasant side effects of chemotherapy experienced by 20-90% of cancer patients. OBJECTIVE: In the present study, the effects of Korean Panax ginseng C.A. Meyer (Araliaceae) (RG), ginseng saponin (GS) and non-saponin (GNS) on cisplatin (CP)-induced pica and gastric damage in rats were investigated. MATERIAL AND METHODS: Rats were treated with RG (25, 50, 100 mg/kg b.wt.), GS (5 and 10 mg/kg 100 mg/kg b.wt.) and GNS (50 and 100 mg/kg b.wt.) before or after a single intraperitoneal injection of CP (6 mg/kg b.wt.). Kaolin together with normal food intake, normal food alone, body weight, histological examination of stomach and small intestine were used as indices of CP-induced pica in rats. RESULTS: Pre-treatment with RG (50 and 100 mg/kg b.wt.) attenuated CP-induced kaolin intake at 24 h. CP-induced kaolin intake decreased upon post-treatment of rats with RG (50 and 100 mg/kg b.wt.) at 48 h. The incidence of body weight reduction at 48 and 72 h diminished in rats post-treated with RG (50 mg/kg b.wt.). Pre-treatment with GS (5 and 10 mg/kg b.wt.) and GNS (50 and 100 mg/kg b.wt.) attenuated CP-induced kaolin intake while normal food intake was not improved in 24 and 48 h. DISCUSSION AND CONCLUSION: The gastro-protective effects of RG, GS and GNS were further confirmed by histopathological (damage in glandular portion and villi with dilated appearance) findings. The study indicates that both the red GS and GNS improve feeding behavior against CP-induced pica in rats.

[Preventive and therapeutic effects of xiaobanxia fuling decoction on cisplatin-induced pica rats].

OBJECTIVE: To investigate the preventive and therapeutic effects of Xiaobanxia Fuling Decoction (XBFD) on cisplatin-induced pica rats and to study its mechanism. METHODS: Forty-two male Sprague-Dawley rats were randomly divided into the following 7 groups, i.e., the blank control group, the model group, the high-, middle-, and low-dose XBFD groups (at the daily dose of 30, 15, and 7. 5 g/kg, respectively), the aprepitant (at the daily dose of 13 mg/kg), and pure Chinese medicine group (at the daily dose of XBFD 15 g/kg), 6 in each group. On the 3rd day of this study, 3 mg/kg cisplatin was intraperitoneally injected to rats except the blank control group and the model group to establish the pica rat model. The consumptions of kaolin, food, and the general situation of rats were observed. The protein and mRNA expressions of neurokinin 1 receptor (NK1R) in both the medulla oblongata and the gastric antrum were measured by immunohistochemical assay and Real-time fluorescent quantitative PCR respectively on the sixth day of this study. RESULTS: On the third, fourth, and fifth day of this study, the consumption of kaolin of rats significantly increased when compared with the blank control group (P<0.01). Compared with the model group, the consumption of kaolin significantly decreased in the high-, middle-, and low-dose XBFD groups on the third, fourth, and fifth day of this study (P<0.05). The food intake of rats in the high-dose XBFD groups significantly increased when compared with the model group on the third day of this study (P<0.05). The protein and mRNA expressions of NK, R in the medulla oblongata and the gastric antrum significantly decreased in the high- and middle-dose XBFD groups when compared with the model group (P<0.05). CONCLUSIONS: XBFD could prevent and treat cisplatin-induced pica in rats. Its effect might be correlated with decreasing expressions of NK, R in the medulla oblongata and the gastric antrum.

Acute oxycodone induces the pro-emetic pica response in rats.

Oxycodone, a semisynthetic opioid analgesic, is frequently prescribed for the management of pain. Side effects of nausea and emesis affect patient compliance and limit its therapeutic use. The present study established that an antinociceptive dose of oxycodone (15 mg/kg; oral) induces the pica response. We found sex differences in the temporal course of pica, with females having a longer duration. Opioid receptors mediated the pica response, as 1.0 mg/kg naloxone transiently attenuated and 2.0 mg/kg naloxone blocked pica. A κ-selective antagonist failed to block the response, suggesting mediation by µ opioid receptor. For further validation, we used the well established kaolin intake model to assess pica with the chemotherapeutic drug cisplatin as a positive control. Oxycodone and cisplatin significantly increased kaolin intake 4- to 7-fold, and the wet weight of stomach was elevated 2- to 3-fold. To examine the underlying neural circuitry, we investigated c-fos activation in the area postrema and nucleus of solitary tract (NTS). Oxycodone treatment significantly increased the number of c-fos-positive neurons in the area postrema and NTS compared with water controls. As expected, cisplatin also increased the number of c-fos-positive cells in these regions. In the area postrema, the oxycodone effect was greater than cisplatin, especially at 2 h. These results indicate that an antinociceptive dose of oxycodone is associated with the expression of pica, a pro-emetic response.

Xiao-Ban-Xia-Tang inhibits cisplatin-induced pica by down regulating obestatin in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Xiao-Ban-Xia-Tang (XBXT), a traditional Chinese herbal medicine, has been used in China for more than 2000 years, and proved to be effective in various cases of vomiting in the clinic. OBJECTIVE: To investigate the inhibitive effect of XBXT on cisplatin-induced pica behaviour and its effective mechanism on obestatin, CCK and CGRP in the pica model of rat. MATERIALS AND METHODS: The inhibitive effect of XBXT was investigated in the pica model of rats induced by cisplatin (3mg kg(-1), i.p.) in 72h observation, the expression of obestatin in the area postrema and ileum was measured by immunohistochemistry and PCR, and the levels of CCK and CGRP in blood were measured by Elisa. RESULTS: The weight of kaolin eaten in rats induced by cisplatin was significantly reduced by pretreatment with XBXT in a dose-dependent manner during the 0-24h and 24-72h periods (P<0.05). XBXT exhibited effective dose-dependent (P<0.05) inhibition on the increase of expression levels of obestatin in both the ileum and area postrema, and markedly suppressed the increase levels of CCK and CGRP in blood induced by cisplatin in a dose-dependent manner (P<0.05). CONCLUSIONS: XBXT has good activity against cisplatin-induced eating kaolin in rats possibly by inhibiting central or peripheral increase of obestatin, or the levels of CCK and CGRP in blood.

[Ameliorative effect of Armillariella tabescens on cisplatin-induced gastrointestinal tract reaction in the rat].

OBJECTIVE: To evaluate the effect of Armillariella tabescens on cisplatin chemotherapy-induced gastrointestinal tract reaction. METHODS: Forty-eight male Sprague-Dawley rats were randomized into control group, model group, low dose Armillariella tabescens group, middle dose Armillariella tabescens group, high dose Armillariella tabescens group and ondansetron group. The rats were injected intraperitoneally with cisplatin to induce pica, and observe the effect of Armillariella tabescens on consumption of kaolin, food, water and body weight. RESULTS: 24-72 h after cisplatin administration, in the middle dose Armillariella tabescens group, the high dose Armillariella tabescens group and the ondansetron group, the kaolin intake was significantly lower than that in the model group, respectively (P<0.05). The most significant difference was between the high dose Armillariella tabescens group [(0.58 +/- 0.23) g/24 h] and the control group [(2.16 +/- 0.98) g/24 h] at 24 h after cisplatin administration. The variables, such as consumption of food during 48-72 h (P<0.05), water during 48-72 h (P<0.05), and body weight at 72 h (P<0.05) in the middle dose Armillariella tabescens group were significantly higher than those in the model group, but no statistically significant difference between the ondansetron group and the model group (P>0.05). CONCLUSIONS: Armillariella tabescens can effectively inhibit the cisplatin-induced pica response, and the middle dose Armillariella tabescens group is significantly better than the model group in improving the food intake reduction, water intake reduction and body weight loss.

Scutellaria baicalensis and a constituent flavonoid, baicalein, attenuate ritonavir-induced gastrointestinal side-effects.

Ritonavir, a protease inhibitor drug, is commonly used in AIDS therapy. As with other chemotherapeutic drugs that cause gastrointestinal adverse effects, ritonavir treatment is associated with significant nausea and vomiting. This study investigated whether Scutellaria baicalensis, and its active flavonoid constituent, baicalein, attenuate the gastrointestinal effects of ritonavir. The effects of herb administration were evaluated in ritonavir-treated rats using a rat pica model, which simulates nausea and vomiting in humans. The effects of herb administration on gastric emptying in rats were also measured. Ritonavir treatment resulted in increased kaolin intake or severe pica, the intensity of which was reduced significantly with S. baicalensis administration (1 mg kg(-1); P<0.05). High-performance liquid chromatography analysis of S. baicalensis showed the presence of an extremely potent flavonoid constituent, baicalein. The study aimed to determine if baicalein contributed to the anti-pica effect of the extract. It was observed that baicalein dose-dependently decreased pica in ritonavir-treated rats (P<0.001). In addition to inducing pica, ritonavir also significantly delayed gastric emptying, which could contribute to ritonavir-induced gastrointestinal dysfunction. When S. baicalensis extract was administered to ritonavir-treated rats the delayed gastric emptying was significantly attenuated (P<0.05). The results suggest that S. baicalensis and the constituent baicalein reduce the gastrointestinal dysfunction caused by ritonavir. It is concluded that S. baicalensis may potentially have a role to play in reducing drug-induced adverse effects.

Polyphenol contents in grape-seed extracts correlate with antipica effects in cisplatin-treated rats.

BACKGROUND: Grape-seed (Vitis spp.) extract (GSE) is a widely used antioxidant dietary supplement. Chemotherapeutic agents such as cisplatin induce oxidative damage in the gastrointestinal tract and cause nausea and vomiting. MATERIALS AND METHODS: A rat model of simulated emesis was used to observe that cisplatin significantly increased kaolin consumption (or pica). Three GSEs from different sources were used in this study. RESULTS: High-performance liquid chromatographic analysis of five major constituents (gallic acid, catechin, epicatechi, procyanidin B2, and epicatechin gallate) revealed that each constituent had different levels in the three GSEs. Extract #1, prepared in the laboratory of the investigators, had the lowest total polyphenol content (27.27 mg/g); Extract #2, obtained from a dietary supplement company in the United States, had a somewhat higher level (35.84 mg/g); and Extract #3, obtained from China, had the highest level (194.21 mg/g). Subsequently these GSEs were intraperitoneally administered in rats to evaluate their ability to decreasing cisplatin induced pica. At 10 mg/kg all three GSEs, with varying degrees of effect, decreased cisplatin-induced pica. The areas under the curves of kaolin intake from time 0 to 72 hours, compared to those in the cisplantin-only group, were reduced 45% for Extract #1 (p < 0.01), 54% for Extract #2 (p < 0.01), and 66% Extract #3 (p < 0.001). CONCLUSIONS: The study data showed variable polyphenol contents and proportions in the three GSEs correlated to variable pharmacologic effects, indicating the importance of standardization of herbal product preparations. However further increasing of the GSE doses reversed the antipica effects of GSEs, probably because of their pro-oxidant effects. Results from this study suggest that an appropriate dose of GSE has therapeutic value in treating cisplatin-induced emesis.

Effects of antioxidant herbs on chemotherapy-induced nausea and vomiting in a rat-pica model.

Nausea and vomiting are significant adverse effects of chemotherapeutic agents like cisplatin, and cause significant patient morbidity. Cisplatin treatment results in oxidant gut injury, which is postulated to be the primary cause of nausea and vomiting. We evaluated the effects of two antioxidant herbs, Scutellaria baicalensis and American ginseng berry, on cisplatin-induced nausea and vomiting using a rat model. Rats react to emetic or nausea-producing stimuli, such as cisplatin, with altered feeding habits, manifested by increased kaolin consumption (pica). We measured pica in rats to quantify cisplatin-induced nausea. We observed that pretreatment of rats with S. baicalensis or ginseng berry extracts resulted in a significant reduction in cisplatin-induced pica. The in vitro free radical scavenging ability of the herbal extract observed in the study, further confirmed the antioxidant action of the herb. We conclude that herbal antioxidants may have a role in attenuating cisplatin-induced nausea and vomiting.

Scutellaria baicalensis extract decreases cisplatin-induced pica in rats.

PURPOSE: Nausea/vomiting are significant side effects associated with the use of chemotherapy in cancer patients. Treatment of nausea/vomiting caused by cisplatin, a potent chemotherapeutic agent and one of the most emetogenic stimuli, requires a combination of different antiemetic drugs. In this study, we investigated the effects of Scutellaria baicalensis, an antioxidant herbal medicine, on cisplatin-induced nausea using a rat model. METHODS: Rats react to emetic/nausea-producing stimuli, such as cisplatin, with altered feeding habits, manifested by pica or increased consumption of kaolin (a type of clay). We measured pica in rats to quantify cisplatin-induced nausea, and to evaluate the antinausea effect of pretreatment with S. baicalensis extract (SbE) given intraperitoneally. RESULTS: Cisplatin at 3 mg/kg induced significant pica accompanied by reduced food intake, suggesting the presence of nausea. Hence, this cisplatin dose was selected for testing the antinausea activity of SbE. Cisplatin-induced pica decreased significantly when animals were pretreated with SbE at doses of 1 mg/kg and 3 mg/kg ( P<0.01). At a higher SbE dose (10 mg/kg), kaolin consumption increased, rather than further decreased, and was significantly different from that in the groups treated with low SbE doses. CONCLUSIONS: SbE pretreatment decreased cisplatin-induced kaolin intake in the rat model of simulated nausea, suggesting that SbE and its active constituent(s) may play a therapeutic role in chemotherapy-induced emesis. Absence of therapeutic effect at the highest tested SbE dose could have been a result of prooxidant activity often associated with excess antioxidant concentration.

[Reappearance of pica symptoms during erythropoietin treatment]. / Reaparición del síntoma pica durante el tratamiento con eritropoietina.

Absolute or functional iron deficiency decreases the effectiveness of erythropoietin in patients undergoing hemodialysis. We describe a patient who developed pica associated to a ferritin level of 800 ng/ml during recombinant human erythropoietin treatment. The symptom subsided after supplementation with iron dextran. Therefore we recommend iron supplementation during the initial phase of treatment with erythropoietin until serum ferritin levels raise above 1000 ng/ml.