Pharmacokinetics, metabolic activation, and lung toxicity of cyclophosphamide in C57/B16 and ICR mice

Chemotherapy-Induced Changes in the Lung Microenvironment: The Role of MMP-2 in Facilitating Intravascular Arrest of Breast Cancer Cells

Previously, we showed that mice treated with cyclophosphamide (CTX) 4 days before intravenous injection of breast cancer cells had more cancer cells in the lung at 3 h after cancer injection than control counterparts without CTX. At 4 days after its injection, CTX is already excreted from the mice, allowing this pre-treatment design to reveal how CTX may modify the lung environment to indirectly affect cancer cells. In this study, we tested the hypothesis that the increase in cancer cell abundance at 3 h by CTX is due to an increase in the adhesiveness of vascular wall for cancer cells. Our data from protein array analysis and inhibition approach combined with in vitro and in vivo assays support the following two-prong mechanism. (1) CTX increases vascular permeability, resulting in the exposure of the basement membrane (BM). (2) CTX increases the level of matrix metalloproteinase-2 (MMP-2) in mouse serum, which remodels the BM and is functionally important for CTX to increase cancer abundance at this early stage. The combined effect of these two processes is the increased accessibility of critical protein domains in the BM, resulting in higher vascular adhesiveness for cancer cells to adhere. The critical protein domains in the vascular microenvironment are RGD and YISGR domains, whose known binding partners on cancer cells are integrin dimers and laminin receptor, respectively.

Amelioration of cyclophosphamide toxicity via modulation of metabolizing enzymes by avocado (Persea americana) extract

OBJECTIVES

Cyclophosphamide (CPA) is highly effective in treating several human tumours and autoimmune disorders; but, it triggers deleterious side effects. Avocado, Persea americana (Mill.), is a widely consumed fruit with pronounced nutritional and medicinal value. Though many studies examined the protective mechanisms of natural products against CPA toxicity, almost none investigated the modulation of CPA metabolism as a potential underlying mechanism for protection. Here, we investigated the modulating effect of avocado extract (AE) on certain CPA metabolizing enzymes and its correlation with the extent of CPA-induced pulmonary toxicity and urotoxicity.

METHODS

Rats received oral AE (0.9 g/kg body weight/day) 7 days before a single CPA injection (150 mg/kg body weight) and continued AE intake for 2, 7 or 28 days to study three phases of CPA-induced urotoxicity and pulmonary toxicity.

KEY FINDINGS

CPA acutely elevated then reduced hepatic microsomal cytochrome P450 2B6 (CYP2B6) content and significantly suppressed bladder and lung glutathione-S-transferase activity. Furthermore, CPA elevated lung myeloperoxidase activity, DNA content and hydroxyproline level and bladder blood content. AE ameliorated CPA-induced derangements through suppression of CYP2B6 and myeloperoxidase and augmentation of glutathione-S-transferase activity in CPA-treated rats.

CONCLUSIONS

AE modulation of CPA metabolizing enzymes and potential anti-inflammatory effect may mitigate CPA-induced toxicity.

Characterization and Validation of a Chronic Model of Cyclophosphamide-Induced Interstitial Cystitis/Bladder Pain Syndrome in Rats

Interstitial cystitis/Bladder Pain Syndrome (IC/BPS) is a chronic inflammatory disease characterized by visceral pain and voiding symptoms. IC/BPS is still an unsolved enigma with ineffective diagnosis criteria and treatment. A main limitation in IC/BPS understanding is the lack of appropriate preclinical model. Cyclophosphamide (CYP) is commonly used as an experimental model for IC/BPS in rodent. However, the proposed models are very aggressive, contrasting with what occurs in clinic, and often associated with severe toxicity and high mortality rate. In addition, visceral pain, the hallmark symptom of IC/BPS, has been validated in only few of them. In this study, we developed a chronic model of CYP-induced IC/BPS in female rat. In our protocol, no severe weight loss occurred and the survival rate was 100%. In accordance to human pathology, chronic CYP-injected rats developed severe painful behavior whereas only sparse inflammation was observed. Inflammatory response was characterized by bladder edema and focal urothelial damage but absence of massive infiltrate. This chronic model showed persistent symptoms indicative for a central sensitization mechanism. We further demonstrate that CYP-induced chronic visceral pain was significantly reduced by curative treatment with clinically relevant compounds (gabapentin, ibuprofen, and Ialuril^®). We therefore developed and validated a rat model of chronic cystitis that shares strong similarity with human non-ulcerative IC/BPS features without overtly affecting the animal health. This model will thus provide mechanistic insights of the disease and help to evaluate therapeutic agents for IC/BPS.

Characterization of Quin-C1 for its anti-inflammatory property in a mouse model of bleomycin-induced lung injury

AIM

To study the in vivo effects of Quin-C1, a highly specific agonist for formyl peptide receptor 2 (FPR2/ALX), in a mouse model of bleomycin (BLM)-induced lung injury.

METHODS

Male ICR mice were injected intratracheally with BLM (d 0), and intraperitoneally with Quin-C1 (0.2 mg/d) or vehicle between d 1 and d 28, during which pulmonary inflammation was monitored. A similar regimen was carried out between d 5 and d 28 to differentiate anti-inflammatory from anti-fibrotic effects. During the treatment, leukocyte numbers in bronchoalveolar lavage fluid (BALF) were counted, and FPR2/ALX transcripts, tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), the mouse keratinocyte-derived chemokine (KC), transforming growth factor β1 (TGF-β1) and C-X-C motif chemokine 10 (CXCL10) expression levels in the lung tissue were also measured. Both hydroxyproline content and histological changes were examined on d 28 to assess the severity of lung fibrosis.

RESULTS

BLM caused a significant increase in expression levels of all the selected cytokines and chemokines, as well as a thickening of the alveolar wall. Treatment with Quin-C1 significantly reduced the neutrophil and lymphocyte counts in BALF, diminished expression of TNF-α, IL-1β, KC, and TGF-β1, and decreased collagen deposition in lung tissue. The treatment also lowered the content of lung hydroxyproline. Quin-C1 did not ameliorate lung fibrosis when the treatment was started 5 d after the BLM challenge, suggesting that the protection may be attributed to its anti-inflammatory effects. Exposure to BLM or BLM plus Quin-C1 did not change the level of FPR2/ALX transcripts (mFpr1, mFpr2, and Lxa4r) in the lung tissue.

CONCLUSION

The results demonstrate an anti-inflammatory role for Quin-C1 in bleomycin-induced lung injury, which may be further explored for therapeutic applications.

Cystitis increases colorectal afferent sensitivity in the mouse

Studies in humans and rodents suggest that colon inflammation promotes urinary bladder hypersensitivity and, conversely, that cystitis contributes to colon hypersensitivity, events referred to as cross-organ sensitization. To investigate a potential peripheral mechanism, we examined whether cystitis alters the sensitivity of pelvic nerve colorectal afferents. Male C57BL/6 mice were treated with cyclophosphamide (CYP) or saline, and the mechanosensitive properties of single afferent fibers innervating the colorectum were studied with an in vitro preparation. In addition, mechanosensitive receptive endings were exposed to an inflammatory soup (IS) to study sensitization. Urinary bladder mechanosensitive afferents were also tested. We found that baseline responses of stretch-sensitive colorectal afferents did not differ between treatment groups. Whereas IS excited a proportion of colorectal afferents CYP treatment did not alter the magnitude of this response. However, the number of stretch-sensitive fibers excited by IS was increased relative to saline-treated mice. Responses to IS were not altered by CYP treatment, but the proportion of IS-responsive fibers was increased relative to saline-treated mice. In bladder, IS application increased responses of muscular afferents to stretch, although no differences were detected between saline- and CYP-treated mice. In contrast, their chemosensitivity to IS was decreased in the CYP-treated group. Histological examination revealed no changes in colorectum and modest edema and infiltration in the urinary bladder of CYP-treated mice. In conclusion, CYP treatment increased mechanical sensitivity of colorectal muscular afferents and increased the proportion of chemosensitive colorectal afferents. These data support a peripheral contribution to cross-organ sensitization of pelvic organs.

Characterization of cyclophosphamide cystitis, a model of visceral and referred pain, in the mouse: species and strain differences

PURPOSE

Existing animal models of visceral pain in the mouse are of limited practical usefulness since they are labor intensive or not visceral specific. Recently a rat model of cyclophosphamide (CP) cystitis was developed that requires only intraperitoneal injection and features inflammation confined to the bladder. We adapted this model for use in multiple mouse strains to investigate the genetic basis of variability in visceral nociception.

MATERIALS AND METHODS

Outbred CD-1 mice and 12 inbred mouse strains were tested for behavioral changes induced by CP (0 to 300 mg/kg intraperitoneally).

RESULTS

We noted that despite the absence of postural changes or abdominal crises in CD-1 mice, CP produced dose dependent decreases in voluntary locomotor activity unaccompanied by ataxia measured on the rotarod test; referred hyperalgesia of the tail base region but not of the hind paw, which was inhibited in dose dependent fashion by morphine (0 to 20 mg/kg); and bladder inflammation corresponding to these behavioral indices. Furthermore, the extent of hypolocomotion was genotype dependent across 12 inbred strains.

CONCLUSIONS

The simple and automatable nature of CP cystitis using hypolocomotion as a dependent measure renders it an attractive model in which to investigate the genetic and physiological bases of visceral pain. Comparison of strain sensitivity to CP induced hypolocomotion with other nociceptive assays suggests that genes specific to visceral nociception may exist.

Using genome-wide mapping in the mouse to identify genes that influence drug response

Differential drug response is most often likely to be a complex trait, controlled by the combined influences of multiple genes and environmental influences. As a result of theoretical and technical limitations, to date, most clinically useful pharmacogenomic studies in humans have been limited to a small number of candidate genes that have a relatively major impact on drug response. Here, the problems involved in identifying genes that underlie drug response in humans are discussed and the power of mouse genetics as a tool for pharmacogenomic discovery is highlighted.

Murine pharmacogenomics: using the mouse to understand the genetics of drug therapy

Pharmacogenomics seeks to understand the genetic basis of interindividual differences in drug disposition and effects. Differential drug response is likely to most often be a complex trait, in which multiple genes contribute with varying strengths to the therapeutic phenotype. Due to technical and economic limitations, pharmacogenomic studies in humans are mainly limited to a small number of candidate genes with relatively major influences on drug response. This review discusses the problems involved in mapping genes underlying drug response in humans and highlights the theoretical and applied uses of mouse genetics to address these important issues.

Delayed toxicity of cyclophosphamide on the bladder of DBA/2 and C57BL/6 female mouse

The present study describes the delayed development of a severe bladder pathology in a susceptible strain of mice (DBA/2) but not in a resistant strain (C57BL/6) when both were treated with a single 300 mg/kg dose of cyclophosphamide (CY). Inbred DBA/2 and C57BL/6 female mice were injected with CY, and the effect of the drug on the bladder was assessed during 100 days by light microscopy using different staining procedures, and after 30 days by conventional electron microscopy. Early CY toxicity caused a typical haemorrhagic cystitis in both strains that was completely repaired in about 7-10 days. After 30 days of CY injection ulcerous and non-ulcerous forms of chronic cystitis appeared in 86% of DBA/2 mice but only in 4% of C57BL/6 mice. Delayed cystitis was characterized by infiltration and transepithelial passage into the lumen of inflammatory cells and by frequent exfoliation of the urothelium. Mast cells appeared in the connective and muscular layers of the bladder at a much higher number in DBA/2 mice than in C57BL/6 mice or untreated controls. Electron microscopy disclosed the absence of the typical discoidal vesicles normally present in the cytoplasm of surface cells. Instead, numerous abnormal vesicles containing one or several dark granules were observed in the cytoplasm of cells from all the epithelial layers. Delayed cystitis still persisted in DBA/2 mice 100 days after treatment. These results indicate that delayed toxicity of CY in female DBA/2 mice causes a bladder pathology that is not observed in C57BL/6 mice. This pathology resembles interstitial cystitis in humans and could perhaps be used as an animal model for studies on the disease.

Cyclophosphamide cystitis in mice: behavioural characterisation and correlation with bladder inflammation

The generation of transgenic 'knock-out' mice which lack genes relevant to pain is becoming increasing common. However, only one visceral pain model, the writhing test, is available in mice. The aim of this study was to adapt cyclophosphamide cystitis, a model of inflammatory visceral pain described in rats, for use in mice, and to characterise its behavioural effects. The toxic metabolites of systemically-administered cyclophosphamide are excreted in the urine, and induce bladder inflammation. We compared the effects of cyclophosphamide (100 and 300 mg/kg i.p., 4 h survival period) and vehicle (saline) in male mice on spontaneous behaviour (4 h continuous video-tape, and a 5-min Open Field test after 4 h). Involvement of the urinary bladder and other abdominal tissues was assessed by macroscopic examination and measurement of Evan's Blue plasma extravasation. Cyclophosphamide (300 mg/kg) produced significant changes in behaviour, including 22 +/- 6 min of 'crises' of visceral pain-related behaviour and a 53% reduction in activity, and also induced haemorrhage and substantial plasma extravasation in the bladder, but no change in other abdominal tissues. We conclude that cyclophosphamide cystitis has many advantages as a model of sub-acute, inflammatory visceral pain in mice. It does not require surgery or intubation, and we have found it to produce consistent, reproducible and quantifiable behavioural changes, which are significantly correlated with the degree of bladder inflammation in the absence of inflammation of other abdominal tissues. Copyright 1999 European Federation of Chapters of the International Association for the Study of Pain.

Biochemical and connective tissue changes in cyclophosphamide-induced lung fibrosis in rats

The present investigation was designed to characterize the biochemical and connective tissue components and to correlate the significance of morphological and biochemical perturbations in cyclophosphamide (CP)-induced lung fibrosis in rats. Lung fibrosis was induced in male Wistar rats by intraperitoneal injection of 20 mg/100 g body weight of CP, and their pneumotoxic derangements were characterized during an early destructive phase followed by a proliferative and synthetic phase. Serum angiotensin-converting enzyme (ACE) activity was higher in CP-treated rats at days 2, 3, 5, 7, and 11, but there was a significant decrease in lung ACE activity during the same time period. Elevated levels of beta-glucuronidase activity were observed in the lung lavage fluid of CP-administered rats days 2, 3, 5, and 7. Lung myeloperoxidase activity was higher in CP rats. Of significance was the presence of collagenase and collagenolytic cathepsin in the lavage fluid of CP rats, when compared with the barely detectable levels in controls. A similar increase in these enzyme activities was also noticed in the lung tissue of CP rats during the same experimental period. Lavage fluid hydroxyproline content was higher in CP rats when compared with controls. Similarly, lung protein and DNA levels were elevated significantly after treatment with CP. The pulmonary histamine and serotonin contents were significantly higher in CP rats. The incorporation of [3H]thymidine into lung total DNA, [3H]proline into lung hydroxyproline, and [35S]sulphate into lung glycosaminoglycan, measured as indicators of lung DNA, collagen, and glycosaminoglycan synthesis, respectively, was also higher in CP groups. Increased levels of hydroxyproline, elastin, hexosamine, total hexose, fucose, sialic acid, and uronic acid in the lungs of rats 14, 28, and 42 days after CP insult were characterized as biomarkers of CP-induced interstitial changes. These findings indicate that CP-induced lung fibrosis results in alterations not only in collagen synthesis and accumulation, but also in glycosaminoglycan and glycoprotein content.

Upregulation of urokinase in alveolar macrophages and lung tissue in response to silica particles

Impaired fibrinolytic activity and persistent fibrin deposits in lung tissue have been associated with lung fibrotic disorders. The present study examined the sources of plaminogen activator (PA) changes induced by a single intratracheal administration of silica particles (5 mg) in the mouse lung. We found in both control and silica-treated animals that amiloride almost totally abolished PA activity in bronchoalveolar lavage (BAL) fluid (BALF), indicating that initial upregulation (from day 1) as well as sustained PA activity (up to day 30) observed in response to silica is related to changes in urokinase-type PA (uPA). The upregulation of BALF uPA activity was associated with a marked and persistent increase in uPA mRNA levels in lung tissue. Changes in uPA expression were also reflected in the BAL cell fraction. A maximal and constant increase in cell uPA activity was associated with the early response to silica, whereas significant but lower upregulation was still noted at the fibrotic stage. From days 3 to 30, a progressive increase in uPA mRNA levels was noted in BAL inflammatory cells elicited by silica. Because the number of BAL neutrophils was strongly correlated with BALF and BAL cell-associated uPA activity, their involvement in uPA upregulation was addressed by inducing neutropenia with cyclophosphamide (200 mg/kg ip) before administration of the silica. Neutrophilic depletion did not, however, reduce, and even increased, the BAL cell-associated uPA activity. At the BALF level, neutropenia did not change PA activity in silica-treated mice, pointing to alveolar macrophages as the principal source of uPA in response to silica. Immunohistochemical stainings identified alveolar macrophages and pneumocytes as uPA-expressing cells in silica-treated animals (day 30). Intense and heterogenous staining was observed in silicotic nodules. These findings indicate that urokinase produced by alveolar macrophages is operative not only at the alveolitis stage but also later in the fibrotic process, produced by silica particles, supporting the role of uPA in fibrogenesis.

Antimutagenicity of eugenol in the rodent bone marrow micronucleus test

The antimutagenic effect of eugenol on the mutagenicity of cyclophosphamide (CP), mitomycin C (MMC), ethyl methanesulfonate (EMS) and benzo[a]pyrene (B[a]P) was assessed in the rodent bone marrow micronucleus test using male Swiss mice. Oral administration of eugenol (0.4% in the diet) for 15 days was found to decrease significantly the frequency of micronucleated polychromatic erythrocytes (MPEs) elevated by CP. No effect was found on the frequency of MPEs elevated by MMC, EMS and B[a]P. The results provide some support for antimutagenic potency of eugenol in vivo.

Modulation of cyclophosphamide-induced early lung injury by curcumin, an anti-inflammatory antioxidant

Cyclophosphamide causes lung injury in rats through its ability to generate free radicals with subsequent endothelial and epithelial cell damage. In order to observe the protective effects of a potent anti-inflammatory antioxidant, curcumin (diferuloyl methane) on cyclophosphamide-induced early lung injury, healthy, pathogen free male Wistar rats were exposed to 20 mg/100 g body weight of cyclophosphamide, intraperitoneally as a single injection. Prior to cyclophosphamide intoxication oral administration of curcumin was performed daily for 7 days. At various time intervals (2, 3, 5 and 7 days post insult) serum and lung samples were analyzed for angiotensin converting enzyme, lipid peroxidation, reduced glutathione and ascorbic acid. Bronchoalveolar lavage fluid was analyzed for biochemical constituents. The lavage cells were examined for lipid peroxidation and glutathione content. Excised lungs were analyzed for antioxidant enzyme levels. Biochemical analyses revealed time course increases in lavage fluid total protein, albumin, angiotensin converting enzyme (ACE), lactate dehydrogenase, N-acetyl-beta-D-glucosaminidase, alkaline phosphatase, acid phosphatase, lipid peroxide levels and decreased levels of glutathione (GSH) and ascorbic acid 2, 3, 5 and 7 days after cyclophosphamide intoxication. Increased levels of lipid peroxidation and decreased levels of glutathione and ascorbic acid were seen in serum, lung tissue and lavage cells of cyclophosphamide groups. Serum angiotensin converting enzyme activity increased which coincided with the decrease in lung tissue levels. Activities of antioxidant enzymes were reduced with time in the lungs of cyclophosphamide groups.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo administration of taurine and niacin modulate cyclophosphamide-induced lung injury

The antiinflammatory, antioxidant activity of taurine and niacin against cyclophosphamide-induced early lung injury in rats was investigated. A single intraperitoneal injection of cyclophosphamide markedly altered the levels of several biomarkers in bronchoalveolar lavage fluid: total protein, albumin, angiotensin converting enzyme, lactate dehydrogenase, lactate, N-acetyl-beta-D-glucosaminidase, alkaline phosphatase, acid phosphatase and lipid peroxidation product were significantly elevated. In contrast, decreased levels of total reduced glutathione (GSH) and ascorbic acid were observed. Cyclophosphamide significantly increased malondialdehyde levels in serum and lung. Significant increases in lung content of lipid hydroperoxides were seen that paralleled the decreased levels of total reduced glutathione and total sulfhydryl groups. Pretreatment of rats with daily intraperitoneal injection of taurine plus niacin 7 days prior to and 2 days after cyclophosphamide insult significantly inhibited the development of lung injury, prevented the alterations in lavage fluid biomarkers associated with inflammatory reactions, with less lipid peroxidation and restoration of antioxidants. In conclusion, our results suggest that taurine and niacin in combination is efficient in blunting cyclophosphamide-induced pulmonary damage.

Acute pneumocyte injury, poly(ADP-ribose) polymerase activity, and pyridine nucleotide levels after in vitro exposure of murine lung slices to cyclophosphamide

Cyclophosphamide (CYC) is a metabolically activated, DNA-alkylating, antitumor agent that causes pulmonary fibrosis. BALB/cN (B) mice are sensitive and C57Bl/6N (C) mice are resistant to CYC-induced fibrosis. Pulmonary bioactivation may contribute to strain sensitivity. Therefore, we tested the intrinsic susceptibility of murine lung slices to cell injury by direct exposure to CYC for 2-8 hr. Injury was measured by release of lactate dehydrogenase (LDH). DNA damage activates the nuclear enzyme poly(ADP-ribose) polymerase (PAP, EC 2.4.2.30), causing depletion of its substrate, NAD. NAD can also be decreased by phosphorylation to NADP, as seen with oxidative stress. Depletion of NAD can lead to loss of ATP. Thus, we measured LDH release, PAP activation, NAD, NADP and ATP in slices incubated with or without the PAP-inhibitor, 3-aminobenzamide (3-AB). CYC (0.1 to 1.0 mg/mL for 4-8 hr) caused LDH release in slices from both murine strains, but LDH release was significantly greater in B lung slices than in C slices. After an 8-hr incubation 63.9 +/- 3.7% (mean +/- SEM) of total LDH was released from B lung slices with 1.0 mg CYC/mL, whereas only 45.8 +/- 2.6% was released from C lung slices (P < 0.05). 3-AB reduced LDH release to 44.7 +/- 2.4% in B slices and 28.1 +/- 2.0% in C slices (P < 0.05 vs CYC only). PAP activity in nuclei isolated from CYC-treated B lung slices was increased 2- to 4-fold after 2 hr of incubation with 0.5 and 1.0 mg CYC/mL. PAP activation was delayed and reduced with incubation in 3-AB. PAP was activated 2-fold in nuclei from C slices treated with 0.5 mg CYC/mL for 2 hr. NAD was decreased at 2 and 4 hr in B slices treated with 0.5 and 1.0 mg CYC/mL, and at 4 hr with 0.1 mg CYC/mL. NAD depletion occurred only at 4 hr in the resistant C slices treated with 1.0 mg CYC/mL. CYC increased NADP by a similar extent in B and C lung slices. In B slices, NAD losses were approximately 4 times the increases in NADP. CYC did not decrease ATP in B slices and ATP dropped 25% only after 4 hr in the resistant C slices. We conclude that CYC is directly toxic to lung tissue and observe that strain sensitivity in vitro mirrors the sensitivity to fibrosis in vivo. PAP activation and oxidative stress may contribute to this toxicity.

Murine strain differences in metabolism and bladder toxicity of cyclophosphamide

Cyclophosphamide (CP) undergoes metabolic activation, generating phosphoramide mustard and acrolein which are believed to be responsible for the cytostatic and toxic effects, respectively. In this study, CP-induced bladder toxicity (hemorrhagic cystitis) was found to be significantly greater in the ICR than the C57BL/6N (C-57) strain of mice. Strain differences exist in the distribution of CP metabolites to the bladder, as evidenced by consistently higher levels of acrolein equivalents measured in the urine of the sensitive ICR strain. These differences may arise from strain variation in the oxidative metabolism of CP by the mixed-function oxidase system. However, intrinsic factors within the bladder may also be involved in the resistance exhibited by C-57 mice. Support for this hypothesis is provided by the significant increase in hemorrhagic response and permeability of ICR compared to C-57 bladders exposed to equivalent levels of acrolein by intravesicle instillation. Basal protein thiol levels were higher in C-57 than in the ICR strain. However, the effects of acrolein on protein thiol content did not correlate with toxicity suggesting that these groups are not the critical targets for CP-induced bladder injury.