Neuroprotective, immunosuppressant and antineoplastic properties of mTOR inhibitors: current and emerging therapeutic options.

The acronym mTOR defines a family of serine-threonine protein kinase called mammalian target of rapamycin. The major role of these kinases in the cell is to merge extracellular instructions with information about cellular metabolic resources and to control the rate of anabolic and catabolic processes accordingly. In mammalian cells mTOR is present in two distinct heteromeric protein complexes commonly referred to as mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2), involved in the control of a wide variety of cellular processes. It has been recently reported that compounds acting modulating mTOR activity, beside mediating the well recognized processes exploited in the anticancer and immunosuppressant effects, are provided with neuroprotective properties. In fact, mTOR is involved in the mechanism of PI3K/Akt-induced upregulation of glutamate transporter 1, GLT1, that is linked to several neuronal disorders such as stroke, Alzheimer's disease, and amyotrophic lateral sclerosis. Furthermore, in adult brain mTOR is crucial for numerous physiological processes such as synaptic plasticity, learning, memory, and brain control of food uptake. Moreover, the activation of mTOR pathway is involved in neuronal development, dendrite development and spine morphogenesis.

Evalutation of mycophenolic acid systemic exposure by limited sampling strategy in kidney transplant recipients receiving enteric-coated mycophenolate sodium (EC-MPS) and cyclosporine.

BACKGROUND: Enteric-coated mycophenolate sodium (EC-MPS) and mycophenolate mofetil (MMF) are prodrugs of mycophenolic acid (MPA). Although many patients still receive MMF as an inosine monophosphate dehydrogenase inhibitor, EC-MPS could be considered a reliable alternative to MMF in the immunosuppressive protocols of kidney transplant recipients. MPA shows high pharmacokinetic variability and consequently a 12-h area under the curve (AUC(0-12)) should be used to guide the therapeutic dosage. However, patient compliance and economic costs make MPA AUC(0-12) an unpractical approach. Limited sampling strategies or predictive systemic drug exposure equation models based on limited sampling times are available only for MMF but lack for EC-MPS. METHODS: The present study enrolled 26 kidney transplant recipients receiving EC-MPS as part of their immunosuppressive therapy. Twenty-six full MPA AUC(0-12) were performed. By using multiple stepwise regression analysis, we obtained several predictive equations of MPA systemic exposure in this group of patients. The value of the selected equations was tested in a subsequently enrolled group of 26 kidney transplant recipients. RESULTS: The best equations obtained in the first group of patients were the following: 22.906 + 3.880·C(0) + 1.117·C(1) + 7.527·C(8) (r = 0.901) and 35.064 +3.784·C(0) + 1.002·C(1) + 1.192·C(2) (r = 0.846). These equation models showed an optimal agreement between the full AUCs and estimated AUCs by using the validation group of patients. CONCLUSIONS: Limited sampling strategies are useful for MPA AUC(0-12) estimation in patients receiving EC-MPS and cyclosporine. The choice of one or the other equation model depends on the pharmacokinetic characteristics of the patients, in particular the potential presence of enterohepatic recirculation.

Analytical and pharmacological aspects of therapeutic drug monitoring of mTOR inhibitors.

Mammalian Target Of Rapamycin (mTOR) inhibitors represent a new class of immunosuppressant drugs extensively used for the prevention and the treatment of graft rejection in organ transplant recipients. Their current use is due to referred low nephrotoxic effects, particularly important in kidney transplanted and/or patients with renal failure. The most representative drugs of such class are Sirolimus (Siro) and Everolimus (Rad). Both drugs show a narrow therapeutic window, therefore, monitoring of whole-blood drug levels is recommended in order to optimize the therapy. Among the available assays, Liquid Chromatography coupled with UltraViolet or Electrospray Tandem Mass Spectrometry methods (LC/UV or LC/ESI-MSMS) are the most accurate and specific ones. A reliable alternative is represented by immunoassays, which offer the opportunity to minimize sample pre-treatment, thus reducing the time between drawing blood sample and measuring the drug concentration, an important aspect in high-throughput analyses. Despite this, a limitation in the use of immunoassays for therapeutic drug monitoring is the lower specifity compared with the chromatographic methods when analysing structurally-related drugs. New insights to optimize mTOR inhibitors regimens seem to be offered by the evaluation of CYP450 3A activity by using the probe drug approach. To such purpose, there are a number of major probe drugs used for in vivo studies including: midazolam, cortisol, lidocaine, nifedipine, dextromethorphan, erythromycin, dapsone and alfentanil. The aim of the present paper is to report the most recent knowledge concerning this issue, supplying a critical and comprehensive review for whom are involved both in the clinical and analytical areas.

Cigarette smoke condensate causes a decrease of the gene expression of Cu-Zn superoxide dismutase, Mn superoxide dismutase, glutathione peroxidase, catalase, and free radical-induced cell injury in SH-SY5Y human neuroblastoma cells.

Cigarette smoking condensate (CSC) contains oxidant compounds able to generate superoxide. The aim of the present study was to investigate the effect of the exposure to CSC on: (1) free radical production, (2) the gene expression of the antioxidant enzymes Cu-Zn superoxide dismutase (SOD1), Mn superoxide dismutase (SOD2), Glutathione Peroxidase (GPx), and catalase (CAT), and (3) cell survival in human neuroblastoma SH-SY5Y cells. The results showed that exposure (24 h) to different concentrations (10-150 µg/ml) of CSC caused a dose dependent cell injury that was coupled to the maximal increase of free radical production. These events were prevented by the addition to the incubation medium of the scavenger Vitamin E (50 µM). Furthermore, CSC exposure caused a reduction of the gene expression of the antioxidant enzymes SOD1, SOD2, GPx, and CAT that was counteracted by Vitamin E (50 µM). These results suggest that CSC exposure can induce a free radical overcharge that may be responsible for the inhibition of antioxidant enzymes expression and cell injury in SH-SY5Y human neuroblastoma cells. In fact the scavenger vitamin E can block both cell injury and inhibition of SOD1, SOD2, GPx, and CAT induced by CSC exposure.

Absence of pharmacokinetic interference of moxifloxacin on cyclosporine and tacrolimus in kidney transplant recipients.

This study investigates the potential pharmacokinetic interactions between an antimicrobial agent, moxifloxacin, and 2 immunosuppressant drugs, cyclosporine and tacrolimus, in kidney transplant recipients. Twenty-two kidney transplant patients needing antibiotic therapy for urinary tract infections are enrolled. Eleven patients are under cyclosporine treatment and the other 11 patients are under tacrolimus treatment. Because the urinary tract infections are caused by gram-negative aerobes sensitive to moxifloxacin, this antibiotic is administered by oral route at a dose of 400 mg/d for 1 week; in each patient pharmacokinetic studies are carried out before and at the seventh day of therapy. For both immunosuppressors, none of the pharmacokinetic parameters investigated show statistically significant differences between values obtained before and during treatment with moxifloxacin. In fact, the concentration-time profiles of monoclonal cyclosporine, polyclonal cyclosporine, and tacrolimus are not significantly different before and during the antimicrobial therapy. The results of the present study rule out interference of moxifloxacin with both cyclosporine and tacrolimus kinetics and indicate that the concomitant administration of the fluoroquinolone and cyclosporine or tacrolimus does not require modifications of the dosages of 2 immunosuppressant drugs.

EC-MPS permits lower gastrointestinal symptom burden despite higher MPA exposure in patients with severe MMF-related gastrointestinal side-effects.

Gastrointestinal (GI) adverse events in renal transplant patients are a common cause of mycophenolate mofetil (MMF) dose reductions, which result in an increased risk of graft rejection because of a low immunosuppression. This study investigated whether conversion from MMF to enteric-coated mycophenolate sodium (EC-MPS) in renal transplant patients with serious GI side-effects, alleviated these symptoms and allowed administration of higher doses of EC-MPS. Nineteen renal transplant patients with severe MMF-related GI side-effects underwent a progressive reduction in MMF dose until symptoms disappeared. At this point, 12-h AUC(MMF) was evaluated and patients were shifted to an equimolar dose of EC-MPS. The EC-MPS dose was then progressively increased until the highest recommended dose was reached or GI symptoms re-appeared. Four weeks post-conversion, AUC(EC-MPS) was determined. Conversion led to a mean increase in EC-MPS dose of 68% (P < 0.0001), with a corresponding rise in AUC(0-12) (60.5%, P < 0.0006) associated with significant benefits in terms of both quality of life (Kidney Transplant Questionnaire, P < 0.01) and GI symptoms (Gastrointestinal Symptom Rating Scale, P < 0.0001), using validated questionnaires. In five of 19 patients, the EC-MPS dose could not be increased because of the prompt insurgence of GI symptoms. Renal function and biochemical parameters remained stable post-conversion and no rejection episodes occurred. These findings suggest that, in selected patients, EC-MPS may be better tolerated than MMF when GI symptoms are particularly important and permits higher mycophenolic acid exposure, when required.

Effects of particulate matter (PM(10), PM(2.5) and PM(1)) on the cardiovascular system.

Several studies have demonstrated that exposure to particulate matter (PM) of different size fractions is associated with an increased risk of cardiovascular disease (CVD). In this review, we have taken into consideration the possible correlation between the "short term" and "long term" effects of PM exposure and the onset of CVDs as well as the possible molecular mechanisms by which PM elicits the development of these events. Particularly, it is here underlined that these adverse health effects depend not only on the level of PM concentration in the air but also on its particular internal composition. Furthermore, we have also synthesized the findings gleaned from those few studies indicating that PM produced by tobacco smoke can give rise to cardiovascular injury.

A prospective study of acute drug-induced liver injury in patients suffering from non-alcoholic fatty liver disease.

AIM: Liver damage due to facultative hepatotoxins is scarcely foreseeable. We evaluated the prevalence of acute drug-induced liver injury (DILI) in a specific setting, assessing eventual interactions with pre-existing hepatic illnesses. METHODS: The research was carried out in an Italian tertiary care hospital, by analyzing 248 patients with non-advanced liver disease, divided into two well-matched groups: 174 patients (median age 53, 94 females) with hepatitis C virus-related chronic hepatitis; and 74 (median age 55, 39 females) with non-alcoholic fatty liver disease (NAFLD). RESULTS: Six patients (2.4% of the whole population) belonging to the NAFLD group (chi(2)-test, P = 0.004) suffered from acute hepatoxicity related to the following drugs, that is antihypertensive, acting on platelet aggregation, antimicrobial, non-steroidal anti-inflammatory and proton pump inhibitor. The NAFLD presence was an independent risk factor in determining drug-related acute hepatitis, with an odds ratio of 3.95 (95% confidence intervals: 11.48-1.35). Central obesity was relevant in every patient with acute toxicity. Alcohol consumption and drug association did not influence the acute drug-induced liver damage. CONCLUSION: NAFLD conveys a nearly fourfold increase of DILI risk in obese middle-aged patients. NAFLD, characterized by mitochondrial dysfunction, could predispose to drug-induced hepatotoxicity that probably shares the same pathophysiological mechanism.

Reliability of total overnight salivary caffeine assessment (TOSCA) for liver function evaluation in compensated cirrhotic patients.

BACKGROUND AND AIMS: Systemic caffeine clearance is considered the gold standard for phenotyping cytochrome P450 1A2 in epidemiological studies, and has been recommended for the non-invasive assessment of liver function in chronic liver disease. Our aim was to find a valid, simple and reliable alternative to this method, and therefore focused our attention on the measurement of an unique salivary caffeine concentration, without drug exposure. METHODS: Our evaluation included 36 healthy controls, 47 patients with compensated liver cirrhosis of viral origin, and 48 obese and diabetic patients with cryptogenetic (likely metabolic) cirrhosis. All shared the same caffeine consumption habits (regular daily use of caffeinated beverages, mainly coffee). The total overnight salivary caffeine assessment (TOSCA) was determined by using a single-point concentration of salivary caffeine, after an overnight period of abstinence. RESULTS: Daily routine caffeine intake of our population was adequate for studying the TOSCA. This single-point concentration correlated well with caffeine clearance, measured by salivary concentrations of caffeine. Mean TOSCA in cirrhotic patients was significantly higher than in controls (p<0.001; sensitivity (%) 84.2 and specificity (%) 97.2; negative likelihood ratio=0.16 and positive likelihood ratio=30.32). A cut-off set at 4.2 microg/ml (sensitivity (%) 95.8 and specificity (%) 68.1; negative likelihood ratio=0.06 and positive likelihood ratio=3.0) successfully differentiated the type of cirrhosis. Rapid (with higher metabolism of caffeine) metabolizers were more frequent in the group of patients with cirrhosis of metabolic origin (70.8%; p<0.0001), and the opposite was true for the group of patients with cirrhosis of viral origin, which comprised many poor metabolizers (85.1%; p<0.001). Serum transforming growth factor-beta 1 concentration, mirroring ongoing fibrosis, ranked high in poor metabolizers. The association between overnight assessment and homeostasis model assessment in rapid metabolizers could result from similar roles for cytochrome P450 1A2 and insulin resistance in determining metabolic liver cirrhosis. CONCLUSION: The TOSCA, although differential between the viral and metabolic etiologies, could be considered a good diagnostic use to verify the presence and eventually the type of compensated liver cirrhosis.