Dose-limiting Complication Research Articles

Development of an easy-to-handle murine model for the characterization of radiation-induced gross and molecular changes in skin.

BackgroundRadiation-induced skin injury is a dose-limiting complication of radiotherapy. To investigate this problem and to develop a framework for making decisions on treatment and dose prescription, a murine model of radiation-induced skin injury was developed.MethodsThe dorsal skin of the mice was isolated, and irradiation was applied at single doses of 15, 30, and 50 Gy. The mice were followed for 12 weeks with serial photography and laser Doppler analysis. Sequential skin biopsy samples were obtained and subjected to a histological analysis, immunostaining against transforming growth factor beta (TGF-β), and Western blotting with Wnt-3 and β-catenin. Increases in the levels of TGF-β, Wnt, and β-catenin were detected after irradiation.ResultsAll tested radiation doses caused progressive dermal thickening and fibrosis. The cause of this process, however, may not be radiation alone, as the natural course of wound healing may elicit a similar response. The latent appearance of molecular and histological markers that induce fibrosis in the 15 Gy group without causing apparent gross skin injuries indicates that 15 Gy is an appropriate dose for characterizing the effects of chronic irradiation alone. Thus, this model best mimics the patterns of injury that occur in human subjects.ConclusionsThis animal model can be used to elucidate the gross and molecular changes that occur in radiation-induced skin injury and provides an effective platform for studying this adverse effect without complicating the process of wound healing.

Topical sildenafil in the treatment of hand-foot syndrome and hand-foot skin reaction: A retrospective study.

e22095Background: Hand-foot syndrome (HFS) and hand-foot skin reaction (HFSR) are painful, debilitating, and often dose-limiting complications of anticancer agents. These cutaneous reactions are en...

Rosmarinic Acid Mitigates Mitochondrial Dysfunction and Spinal Glial Activation in Oxaliplatin-induced Peripheral Neuropathy.

Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting complication which develops as a consequence of treatment with chemotherapeutic agents like oxaliplatin and is a mainstay of therapy for colorectal cancer. Ever since CIPN was identified, understanding its exact pathomechanisms remains a clinical challenge. The role of mitochondrial dysfunction and glial cell activation has surfaced in the etiology of CIPN. Rosmarinic acid (RA), a known mitoprotectant exerts neuroprotection against the oxidative stress and neuroinflammation in various disease conditions. Hence, in the present study, we investigated the effect using rosmarinic acid (25 and 50mg/kg, po) in the experimental model of oxaliplatin-induced peripheral neuropathy (OIPN) in rats. Results showed that RA significantly (p < 0.001) prevented the functional deficits, reversed oxaliplatin-induced mechanical allodynia and cold hyperalgesia in rats. It reduced the oxidative stress, improved the mitochondrial function, and prevented the oxaliplatin-induced loss of ATP levels. RA significantly (p < 0.01) inhibited the spinal glial cell activation and suppressed the expression of inflammatory markers. RA treatment also resulted in the activation of adenosine monophosphate-activated protein kinase (AMPK) in the peripheral nerves and dorsal root ganglion (DRG) which also might have contributed to its neuroprotective actions. In vitro screening also revealed that RA did not compromise the anti-cancer activity of oxaliplatin in colon cancer cells (HT-29). Taken together, the above results demonstrate the therapeutic activity of RA against the oxaliplatin-induced mitochondrial dysfunction and neuroinflammation and thus, suggest its potential for the management of OIPN. Graphical Abstract Schematic representation of neuroprotective mechanisms of rosmarinic acid via AMPK activation in oxaliplatin-evoked peripheral neuropathy.

Strategies in management of oral mucositis

Oral mucositis is a clinically important and sometimes dose-limiting complication of cancer therapy. Mucositis lesions are painful, affect nutrition and quality of life and often hamper continuity of the treatment modality. The pathogenesis of oral mucositis is multifactorial and complex. This is a review paper which discusses various aspects a clinician should know in management of mucositis.

Pulmonary toxicity generated from radiotherapeutic treatment of thoracic malignancies.

Radiation-induced lung injury (RILI) remains a major obstacle for thoracic radiotherapy for the treatment of lung cancer, esophageal cancer and lymphoma. It is the principal dose-limiting complication, and can markedly impair the therapeutic ratio as well as a patient's quality of life. The current review presents the relevant concepts associated with RILI, including the pathogenic mechanisms and the potential treatment strategies, so as to achieve a general understanding of this issue. RILI comprises an acute radiation pneumonitis phase and subsequent late lung fibrosis. The established assessment criteria are clinical manifestations, imaging changes and the necessity for medical assistance. Risk factors are also considered in order to optimize treatment planning. Due to the underlying molecular mechanisms of RILI, the present review also discusses several targeted pharmacological approaches for its treatment, as well as corticosteroid therapy.

Progesterone receptor, a novel risk factor for paclitaxel-induced peripheral neuropathy.

e12031Background: Peripheral neuropathy is the main dose-limiting complication of paclitaxel. In this study, the association between clinical characteristics of the patients with breast cancer, dis...

β-Arrestin-2 modulates radiation-induced intestinal crypt progenitor/stem cell injury

Intestinal crypt progenitor/stem (ICPS) cell apoptosis and vascular endothelial cell apoptosis are responsible for the initiation and development of ionizing radiation (IR)-evoked gastrointestinal syndrome. The signaling mechanisms underlying IR-induced ICPS cell apoptosis remain largely unclear. Our findings provide evidence that β-arrestin-2 (βarr2)-mediated ICPS cell apoptosis is crucial for IR-stimulated intestinal injury. βArr2-deficient mice exhibited decreased ICPS cell and intestinal Lgr5+ (leucine-rich repeat-containing G-protein-coupled receptor 5-positive) stem cell apoptosis, promoted crypt proliferation and reproduction, and protracted survival following lethal doses of radiation. Radioprotection in the ICPS cells isolated from βarr2-deficient mice depended on prolonged nuclear factor-κB (NF-κB) activation via direct interaction of βarr2 with IκBα and subsequent inhibition of p53-upregulated modulator of apoptosis (PUMA)-mediated mitochondrial dysfunction. Unexpectedly, βarr2 deficiency had little effect on IR-induced intestinal vascular endothelial cell apoptosis in mice. Consistently, βarr2 knockdown also provided significant radioresistance by manipulating NF-κB/PUMA signaling in Lgr5+ cells in vitro. Collectively, these observations show that targeting the βarr2/NF-κB/PUMA novel pathway is a potential radiomitigator for limiting the damaging effect of radiotherapy on the gastrointestinal system. Significance statement: acute injury to the intestinal mucosa is a major dose-limiting complication of abdominal radiotherapy. The issue of whether the critical factor for the initiation of radiation-induced intestinal injury is intestinal stem cell apoptosis or endothelial cell apoptosis remains unresolved. βArrs have recently been found to be multifunctional adaptor of apoptosis. Here, we found that β-arrestin-2 (βarr2) deficiency was associated with decreased radiation-induced ICPS cell apoptosis, which prolonged survival in abdominally irradiated mice. Moreover, βarr2 deficiency-mediated intestinal progenitor/stem cell radioprotection relied on protracted NF-κB activation and subsequent suppression of PUMA induction. Our results suggest that ICPS cell apoptosis is the factor involved in the initiation and development of radiation-induced gastrointestinal syndrome. βArr2 is a potential target for lessening radiation-induced ICPS cell apoptosis.

Wen-Luo-Tong Prevents Glial Activation and Nociceptive Sensitization in a Rat Model of Oxaliplatin-Induced Neuropathic Pain.

One of the main dose-limiting complications of the chemotherapeutic agent oxaliplatin (OXL) is painful neuropathy. Glial activation and nociceptive sensitization may be responsible for the mechanism of neuropathic pain. The Traditional Chinese Medicine (TCM) Wen-luo-tong (WLT) has been widely used in China to treat chemotherapy induced neuropathic pain. However, there is no study on the effects of WLT on spinal glial activation induced by OXL. In this study, a rat model of OXL-induced chronic neuropathic pain was established and WLT was administrated. Pain behavioral tests and morphometric examination of dorsal root ganglia (DRG) were conducted. Glial fibrillary acidic protein (GFAP) immunostaining was performed, glial activation was evaluated, and the excitatory neurotransmitter substance P (SP) and glial-derived proinflammatory cytokine tumor necrosis factor-α (TNF-α) were analyzed. WLT treatment alleviated OXL-induced mechanical allodynia and mechanical hyperalgesia. Changes in the somatic, nuclear, and nucleolar areas of neurons in DRG were prevented. In the spinal dorsal horn, hypertrophy and activation of GFAP-positive astrocytes were averted, and the level of GFAP mRNA decreased significantly. Additionally, TNF-α mRNA and protein levels decreased. Collectively, these results indicate that WLT reversed both glial activation in the spinal dorsal horn and nociceptive sensitization during OXL-induced chronic neuropathic pain in rats.

An exercise regimen prevents development paclitaxel induced peripheral neuropathy in a mouse model.

Peripheral neuropathy is a major, dose-limiting complication of many chemotherapeutic agents. Currently there is no effective method to prevent development of chemotherapy-induced peripheral neuropathy (CIPN). Recent studies have shown that exercise can improve regeneration of peripheral nerves but its effect in preventing peripheral neuropathy is unknown. In this study, we examined the effect of a rigorous treadmill exercise program that was started 1 week before administration of paclitaxel and continued throughout the study in a mouse model of CIPN. We showed that exercise can partially abrogate features of axonal degeneration induced by paclitaxel including reduction in epidermal nerve fiber density in the plantar hind paw and thermal hypoalgesia. Furthermore, detyrosinated tubulin that is elevated in nerves treated with paclitaxel was normal in exercised animals. This study points to a relatively simple and potentially effective therapeutic option to reduce the neurotoxic effects of chemotherapy.

Spinal neuroimmune activation is independent of T-cell infiltration and attenuated by A3 adenosine receptor agonists in a model of oxaliplatin-induced peripheral neuropathy.

Many commonly used chemotherapeutics including oxaliplatin are associated with the development of a painful chemotherapy-induced peripheral neuropathy (CIPN). This dose-limiting complication can appear long after the completion of therapy causing a significant reduction in quality-of-life and impeding cancer treatment. We recently reported that activation of the Gi/Gq-coupled A3 adenosine receptor (A3AR) with selective A3AR agonists (i.e., IB-MECA) blocked the development of chemotherapy induced-neuropathic pain in models evoked by distinct agents including oxaliplatin without interfering with their anticancer activities. The mechanism(s) of action underlying these beneficial effects has yet to be explored. Our results herein demonstrate that the development of oxaliplatin-induced mechano-hypersensitivity (allodynia and hyperalgesia) in rats is associated with the hyperactivation of astrocytes, but not microglial cells, increased production of pro-inflammatory and neuroexcitatory cytokines (TNF, IL-1β), and reductions in the levels of anti-inflammatory/neuroprotective cytokines (IL-10, IL-4) in the dorsal horn of the spinal cord. These events did not require lymphocytic mobilization since oxaliplatin did not induce CD45(+)/CD3(+) T-cell infiltration into the spinal cord. A3AR agonists blocked the development of neuropathic pain with beneficial effects strongly associated with the modulation of spinal neuroinflammatory processes: attenuation of astrocytic hyperactivation, inhibition of TNF and IL-1β production, and an increase in IL-10 and IL-4. These results suggest that inhibition of an astrocyte-associated neuroinflammatory response contributes to the protective actions of A3AR signaling and continues to support the pharmacological basis for selective A3AR agonists as adjuncts to chemotherapeutic agents for the management of chronic pain.

Grape seed pro-anthocyanidins ameliorates radiation-induced lung injury.

Radiation-induced lung injury (RILI) is a potentially fatal and dose-limiting complication of thoracic radiotherapy. This study was to investigate the protective effects of grape seed pro-anthocyanidins (GSPs), an efficient antioxidant and anti-carcinogenic agent, on RILI. In our study, it was demonstrated that acute and late RILI was ameliorated after GSPs treatment possibly through suppressing TGF-β1/Smad3/Snail signalling pathway and modulating the levels of cytokines (interferon-γ, IL-4 and IL-13) derived from Th1/Th2 cells. In addition, a sustained high level of PGE2 was also maintained by GSPs treatment to limited fibroblast functions. As shown by electron spin resonance spectrometry, GSPs could scavenge hydroxyl radical (•OH) in a dose-dependent manner, which might account for the mitigation of lipid peroxidation and consequent apoptosis of lung cells. In vitro, GSPs radiosensitized lung cancer cell A549 while mitigating radiation injury on normal alveolar epithelial cell RLE-6TN. In conclusion, the results showed that GSPs protects mice from RILI through scavenging free radicals and modulating RILI-associated cytokines, suggesting GSPs as a novel protective agent in RILI.

Amantadine's role in the treatment of levodopa-induced dyskinesia.

Levodopa-induced dyskinesia (LID) is one of the most common and frequently dose-limiting complications of pharmacologic therapy for Parkinson disease (PD). These typically choreiform movements, usually occurring at the time of peak levodopa effect, occur in 40% to 50% of patients after 5 years of therapy but have a reported incidence as high as 94% in a carefully conducted prospective study of patients under treatment for 15 years.1 When mild, LID often goes unnoticed by patients, but moderate or severe forms frequently constitute a major motor or emotional disability. This can lead to reduction or discontinuance of otherwise effective PD therapies and may prompt implementation of more invasive treatments such as deep brain stimulation or direct intrajejunal infusion of levodopa gel. The need for a safe, effective, and enduring means of combating LID is clear. Although many drugs have been evaluated for this purpose and others are currently under investigation, to date only one agent, amantadine, has been effective in an evidence-based medicine review.2

Quantitative assessment of global lung inflammation following radiation therapy using FDG PET/CT: a pilot study

Radiation pneumonitis is the most severe dose-limiting complication in patients receiving thoracic radiation therapy. The aim of this study was to quantify global lung inflammation following radiation therapy using FDG PET/CT. We studied 20 subjects with stage III non-small-cell lung carcinoma who had undergone FDG PET/CT imaging before and after radiation therapy. On all PET/CT studies, the sectional lung volume (sLV) of each lung was calculated from each slice by multiplying the lung area by slice thickness. The sectional lung glycolysis (sLG) was calculated by multiplying the sLV and the lung sectional mean standardized uptake value (sSUVmean) on each slice passing through the lung. The lung volume (LV) was calculated by adding all sLVs from the lung, and the global lung glycolysis (GLG) was calculated by adding all sLGs from the lung. Finally, the lung SUVmean was calculated by dividing the GLG by the LV. The amount of inflammation in the lung parenchyma directly receiving radiation therapy was calculated by subtracting tumor measurements from GLG. In the lung directly receiving radiation therapy, the lung parenchyma SUVmean and global lung parenchymal glycolysis were significantly increased following therapy. In the contralateral lung (internal control), no significant changes were observed in lung SUVmean or GLG following radiation therapy. Global lung parenchymal glycolysis and lung parenchymal SUVmean may serve as potentially useful biomarkers to quantify lung inflammation on FDG PET/CT following thoracic radiation therapy.

Effect of capping chemotherapy dose on chemotherapy effect in morbidly obese women with breast cancer.

1081 Background: Obesity adversely affects outcomes from adjuvant (adj) chemotherapy for breast cancer. Capping of chemotherapy dose has been implicated as one factor that may contribute to this. We postulated that if capping resulted in underdosing, this would be reflected in the incidence of dose dependent toxicities (DDT) such as mucositis and haematological toxicity. Methods: We retrospectively reviewed records of breast cancer patients (pts) commencing adj chemotherapy from 1 Jan 2010-31 Dec 2010 at the Auckland Regional Blood and Cancer Service identified using a prospective pharmacy database. Baseline characteristics, BSA, body mass index (BMI), neutrophil (ANC) nadir, relative dose intensity (RDI) and dose limiting complications (DLC) were recorded. Results: 174 pts were identified. Median age was 49 yrs (24-73). 17.8% had a BSA &gt;2. 3.2% pts with BSA&gt;2 had BMI &lt;30. 42% had a BMI ≥30 (17.9-61.0), of whom 59% had a BSA ≤2. All patients with BSA &gt;2 had dose capping. 71 pts had a DLC. Neutropenic fever/infection or treatment delays from neutropenia were more common if BSA ≤2 vs. &gt;2 (p=0.08) but not with other DDT. Treatment deferrals (18.8 vs. 16.1%) dose reductions (25.2 vs. 32.3%) and mucositis were similar in both groups. Mean baseline ANC was 4.4 in pts with BSA ≤2 and &gt;2. Mean ANC nadir was 0.8 and 1.3 respectively (p&lt;0.01). r2BSA vs nadir ANC was 0.012. G3/4 neutropenia was seen 76.5% of pts with BSA ≤2 vs. 44.8% if BSA &gt;2 (RR 1.3 p&lt;0.01). No pt had &gt; G1 thrombocytopenia. Mean RDI was 93.2 and 94.8 respectively (p=0.4) Conclusions: Previous studies show ANC nadirs correlate well with drug exposure (area under plasma concentration vs. time curve) but poorly with BSA. Therefore we used hematological and DDT as surrogate measures for drug exposure in pts with and without capped doses. There was more G3/4 neutropenia (p&lt;0.01) in uncapped pts but rates of other DDT were similar. Since BSA based dosing has little impact on inter-pt variability in systemic drug exposure and trials where capping was not used still show a poorer outcome in obese pts, these results suggest dose capping is a minor contributor to the worse outcomes in morbidly obese breast cancer pts having adj chemotherapy. Addressing obesity itself may be more important.

Dose reduction (DR) due to chemotherapy induced peripheral neuropathy (CIPN) in breast cancer (BC) patients (pts) in the neoadjuvant/adjuvant settings.

e20574 Background: CIPN is a common and potentially dose-limiting complication of many effective cytotoxic agents. Taxanes are the cornerstone of treatment in BC. Limited data are available regarding the prevalence and severity of DR due to CIPN following taxane use. Methods: Charts of 123 consecutive newly diagnosed BC pts treated with a taxane as part of standard neoadjuvant/adjuvant chemotherapy at the University of Maryland Greenebaum Cancer Center between 01/01/2008 and 12/31/2011 were reviewed. Treating physicians followed standard recommendations for DR. Results: Median age at diagnosis was 53 years (range, 32-78), 120 female/3 male, 48 Caucasian (C), 70 African-American (AA), 5 had a history of alcohol abuse, and 20 had a diagnosis of diabetes mellitus (DM). Seventy pts received docetaxel, 46 paclitaxel, 7 received both or nab-paclitaxel. Fifty (40%) pts required DR, with 21 (17%) due to CIPN and 29 (23%) due to other causes. The median relative dose intensity (received dose/planned dose) for the 21 CIPN-induced dose reduction pts was 88% (range, 62%-97%). A multivariable logistic regression model was used to compare pts who did and did not require DR based on the following possible risk factors: taxane received, DM, alcohol use, and race. Based on the effects estimated by statistical model, there was no difference between pts who did and did not undergo DR with regard to factors listed. However, diabetic pts were over twice as likely to require DR (OR = 2.4, 95% CI: 0.6-10.2, p=0.06). The univariable logistic regression model for 50 pts who had undergone DR revealed possible differences in developing CIPN between C and AA patients. The chances of DR due to CIPN are higher in AA pts (OR=4.3, 95% CI: 1.1-16.7, p=0.03). Pts who received paclitaxel are more likely to require DR due to CIPN than those treated with docetaxel (OR=10.4, 95% CI: 2.7-39.6, p=0.001). Conclusions: 1. CIPN-induced dose-reduction occurred in 17% of our study population. 2. The median relative dose intensity was 88%. 3. DM may increase the overall risk of dose reduction, and AA, paclitaxel therapy may confer a higher risk of CIPN-induced dose reduction.

Expression of Angiotensin II and Aldosterone in Radiation-induced Lung Injury.

ObjectiveRadiation-induced lung injury (RILI) is the most common, dose-limiting complication in thoracic malignancy radiotherapy. Considering its negative impact on patients and restrictions to efficacy, the mechanism of RILI was studied.MethodsWistar rats were locally irradiated with a single dose of 0, 16, and 20 Gy to the right half of the lung to establish a lung injury model. Two and six months after irradiation, the right half of the rat lung tissue was removed, and the concentrations of TGF-β1, angiotensin II, and aldosterone were determined via enzyme-linked immunosorbent assay.ResultsStatistical differences were observed in the expression levels of angiotensin II and aldosterone between the non-irradiation and irradiation groups. Moreover, the expression level of the angiotensin II-aldosterone system increased with increasing doses, and the difference was still observed as time progressed.ConclusionsAngiotensin II-aldosterone system has an important pathophysiological function in the progression of RILI.

Long-term Complications of Therapeutic Exposures in Childhood: Lessons Learned From Childhood Cancer Survivors

* Abbreviations: SMN — : second malignant neoplasms More than 12 000 children and adolescents are diagnosed with cancer each year in the United States.1 Advancements in therapeutic and supportive care strategies have resulted in significant improvements in survival; the overall 5-year survival rate is approaching 80%.1 However, two-thirds of these survivors experience at least one chronic health condition,2 resulting in considerable morbidity and premature mortality among childhood cancer survivors.3 A clear and unambiguous relation exists between therapeutic exposures and specific adverse events experienced by the survivors. A brief overview illustrates the therapeutic exposure–adverse event relation observed in childhood cancer survivors. This overview reinforces the need to develop risk-reduction strategies in childhood cancer survivors, as exemplified by the study conducted by Lipshultz et al4 in this issue of Pediatrics that focuses on use of continuous infusion anthracyclines to reduce the risk of cardiomyopathy. Cardiomyopathy is a dose-limiting complication of anthracyclines5; exposure to cumulative anthracycline doses exceeding 250 mg/m2 increases the risk significantly,6 and younger age, female gender, and exposure to chest irradiation modify this dose-response relation.4 Lungs are particularly susceptible to radiation-induced injury, resulting in pneumonitis and pulmonary fibrosis.7 The incidence and severity of lung damage is related to the total dose of radiation, fractionation of that … Address correspondence to Smita Bhatia, MD, MPH, Department of Population Sciences, City of Hope National Medical Center, 1500 East Duart Rd, Duarte CA 91010. E-mail: sbhatia{at}coh.org

Peritoneal macrophages mediated delivery of chitosan/siRNA nanoparticle to the lesion site in a murine radiation-induced fibrosis model

Background. Radiation-induced fibrosis (RIF) is a dose-limiting complication of cancer radiotherapy and causes serious problems, i.e. restricted tissue flexibility, pain, ulceration or necrosis. Recently, we have successfully treated RIF in a mouse model by intraperitoneal administration of chitosan/siRNA nanoparticles directed towards silencing TNF alpha in local macrophage populations, but the mechanism for the therapeutic effect at the lesion site remains unclear. Methods. Using the same murine RIF model we utilized an optical imaging technique and fluorescence microscopy to investigate the uptake of chitosan/fluorescently labeled siRNA nanoparticles by peritoneal macrophages and their subsequent migration to the inflamed tissue in the RIF model. Results. We observed strong accumulation of the fluorescent signal in the lesion site of the irradiated leg up to 24 hours using the optical imaging system. We further confirm by immunohistochemical staining that Cy3 labeled siRNA resides in macrophages of the irradiated leg. Conclusion. We provide a proof-of-concept for host macrophage trafficking towards the inflamed region in a murine RIF model, which thereby suggests that the chitosan/siRNA nanoparticle may constitute a general treatment for inflammatory diseases using the natural homing potential of macrophages to inflammatory sites.

Potential Role of Poly(ADP-Ribose) Polymerase (PARP) Activation in Methotrexate-Induced Nephrotoxicity and Tubular Apoptosis

Nephrotoxicity is one of the serious dose-limiting complications of methotrexate (MTX) when used in the treatment of various malignancies and nononcological diseases. The aim of this study was to investigate the role of poly(adenosine diphosphate ribose) polymerase (PARP) activity in MTX-induced nephrotoxicity. Rats were divided into 4 groups as control, MTX treated (MTX, 7 mg/kg per d, intraperitoneally [ip], once daily for 3 consecutive days), MTX plus 1,5-isoquinelinediol (ISO, a PARP inhibitor, 3 mg/kg per d, i.p.) treated, or ISO treated. Histopathology of kidneys was evaluated by light microscopy. Terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling assay was used to analyze apoptosis in kidney sections. Blood urea nitrogen (BUN), serum creatinine, and urinary N-acetyl-β-d-glucosaminidase (NAG) were used as biochemical markers of MTX-induced renal injury. Our results showed that MTX administration significantly increased BUN, serum creatinine, and urinary NAG levels. The PARP-1 and PAR (a product of PARP activity) expression and apoptotic cell death were also markedly increased in renal tubules after MTX administration. The ISO treatment attenuated MTX-induced renal injury, as indicated by BUN and serum creatinine levels, urinary NAG excretion, and renal histology. The PARP inhibitor treatment reduced PARP-1 and PAR expression to levels similar to that of controls. These results revealed that ISO may have a protective effect against the nephrotoxic effects of MTX by inhibiting PARP activation. This is the first study that demonstrates the role of PARP activation in MTX-induced nephrotoxicity and tubular apoptosis.

Inhibition of serine palmitoyltransferase delays the onset of radiation-induced pulmonary fibrosis through the negative regulation of sphingosine kinase-1 expression

The enforcement of sphingosine-1-phosphate (S1P) signaling network protects from radiation-induced pneumonitis. We now demonstrate that, in contrast to early postirradiation period, late postirradiation sphingosine kinase-1 (SphK1) and sphingoid base-1-phosphates are associated with radiation-induced pulmonary fibrosis (RIF). Using the mouse model, we demonstrate that RIF is characterized by a marked upregulation of S1P and dihydrosphingosine-1-phosphate (DHS1P) levels in the lung tissue and in circulation accompanied by increased lung SphK1 expression and activity. Inhibition of sphingolipid de novo biosynthesis by targeting serine palmitoyltransferase (SPT) with myriocin reduced radiation-induced pulmonary inflammation and delayed the onset of RIF as evidenced by increased animal lifespan and decreased expression of markers of fibrogenesis, such as collagen and α-smooth muscle actin (α-SMA), in the lung. Long-term inhibition of SPT also decreased radiation-induced SphK activity in the lung and the levels of S1P-DHS1P in the lung tissue and in circulation. In vitro, inhibition or silencing of serine palmitoyltransferase attenuated transforming growth factor-β1 (TGF-β)-induced upregulation of α-SMA through the negative regulation of SphK1 expression in normal human lung fibroblasts. These data demonstrate a novel role for SPT in regulating TGF-β signaling and fibrogenesis that is linked to the regulation of SphK1 expression and S1P-DHS1P formation.