A first-in-class pan-lysyl oxidase inhibitor impairs stromal remodeling and enhances gemcitabine response and survival in pancreatic cancer.

The lysyl oxidase family represents a promising target in stromal targeting of solid tumors due to the importance of this family in crosslinking and stabilizing fibrillar collagens and its known role in tumor desmoplasia. Using small-molecule drug-design approaches, we generated and validated PXS-5505, a first-in-class highly selective and potent pan-lysyl oxidase inhibitor. We demonstrate in vitro and in vivo that pan-lysyl oxidase inhibition decreases chemotherapy-induced pancreatic tumor desmoplasia and stiffness, reduces cancer cell invasion and metastasis, improves tumor perfusion and enhances the efficacy of chemotherapy in the autochthonous genetically engineered KPC model, while also demonstrating antifibrotic effects in human patient-derived xenograft models of pancreatic cancer. PXS-5505 is orally bioavailable, safe and effective at inhibiting lysyl oxidase activity in tissues. Our findings present the rationale for progression of a pan-lysyl oxidase inhibitor aimed at eliciting a reduction in stromal matrix to potentiate chemotherapy in pancreatic ductal adenocarcinoma.

Efficacy and safety of inhaled dry-powder mannitol in adults with cystic fibrosis: An international, randomized controlled study.

BACKGROUND: Mannitol is a mucoactive hyperosmotic agent used as add-on therapy in patients with cystic fibrosis (CF), administered twice-daily (BID) via a small, portable, breath-actuated dry-powder inhaler. This study was conducted to provide confirmatory evidence of mannitol's efficacy and safety in adults. METHODS: This multicenter, double-blind, randomized, parallel-group, controlled clinical trial recruited adults (aged ≥18 years) with CF, and forced expiratory volume in 1 second (FEV1) 40-90% predicted. Subjects received either mannitol 400 mg or mannitol 50 mg (control), BID via dry-powder inhaler for 26 weeks. Primary endpoint: FEV1 averaged over the 26-week treatment period. RESULTS: Of 423 subjects randomized (209 or 214 receiving mannitol 400 mg BID or control, respectively), 373 (88.2%) completed the study, with a similar proportion completing in the two groups. For FEV1 averaged over 26 weeks, mannitol 400 mg BID was statistically superior to control (adjusted mean difference 54 mL [95% CI 8, 100 mL]; p = 0.020). This was supported by sensitivity analyses of the primary endpoint, and by observed improvements in secondary pulmonary function endpoints (eg, absolute adjusted mean difference in percent predicted FEV1 averaged over 26 weeks 1.21% [0.07%, 2.36%]; p = 0.037). Adverse events were mainly mild or moderate in severity, with treatment-related adverse events in 15.5 and 12.2% of subjects receiving mannitol 400 mg BID and control, respectively. CONCLUSIONS: In adults with CF, mannitol 400 mg BID inhaled as a dry-powder statistically significantly improved lung function (FEV1) compared with control, with this improvement supported by sensitivity analyses and secondary pulmonary function endpoints. Mannitol had a good overall safety and tolerability profile. ClinicalTrials.gov: NCT02134353.

Optimising inhaled mannitol for cystic fibrosis in an adult population.

ABSTRACT: There has been remarkable progress in the treatment of cystic fibrosis (CF) patients over the past 20 years. However, limitations of standard therapies have highlighted the need for a convenient alternative treatment to effectively target the pathophysiologic basis of CF-related disease by improving mucociliary clearance of airway secretions and consequently improve lung function and reduce respiratory exacerbations. Mannitol is an osmotic agent available as a dry powder, dispensed in a convenient disposable inhaler device for the treatment of adult patients with CF. Inhalation of mannitol as a dry powder is thought to change the viscoelastic properties of airway secretions, increase the hydration of the airway surface liquid and contribute to increased mucociliary and cough clearance of retained secretions. In two large phase 3 studies [1, 2], long-term use of inhaled mannitol resulted in a significant and clinically meaningful improvement in lung function relative to control in adult CF subjects and had an acceptable safety profile. Clinical experience with inhaled mannitol confirms that it is safe and effective. A minority of patients are unable to tolerate the medication. However, through training in proper inhaler technique and setting clear expectations regarding therapeutic effects, both the tolerance and adherence necessary for long term efficacy can be positively influenced. EDUCATIONAL AIMS: To discuss the importance of airway clearance treatments in the management of cystic fibrosis.To describe the clinical data that supports the use of mannitol in adult patients with cystic fibrosis.To highlight the role of mannitol tolerance testing in screening for hyperresponsiveness.To provide practical considerations for patient education in use of mannitol inhaler. KEY POINTS: Inhaled mannitol is a safe and effective option in adult patients with cystic fibrosis.Mannitol tolerance testing effectively screens for hyperresponsiveness prior to initiation of therapy.Physiotherapists and respiratory therapists play an integral role in the introduction and maintenance of dry powder inhalation therapy.Patient training and follow-up is important for optimising longer term adherence.

Inhaled mannitol for non-cystic fibrosis bronchiectasis: a randomised, controlled trial.

RATIONALE: Bronchiectasis is characterised by excessive production of mucus and pulmonary exacerbations. Inhaled osmotic agents may enhance mucociliary clearance, but few long-term clinical trials have been conducted. OBJECTIVES: To determine the impact of inhaled mannitol on exacerbation rates in patients with non-cystic fibrosis (CF) bronchiectasis. Secondary endpoints included time to first exacerbation, duration of exacerbations, antibiotic use for exacerbations and quality of life (QOL) (St George's Respiratory Questionnaire, SGRQ). METHODS: Patients with non-CF bronchiectasis and a history of chronic excess production of sputum and ≥2 pulmonary exacerbations in the previous 12 months were randomised (1:1) to 52 weeks treatment with inhaled mannitol 400 mg or low-dose mannitol control twice a day. Patients were 18-85 years of age, baseline FEV1 ≥40% and ≤85% predicted and a baseline SGRQ score ≥30. MAIN RESULTS: 461 patients (233 in the mannitol and 228 in the control arm) were treated. Baseline demographics were similar in the two arms. The exacerbation rate was not significantly reduced on mannitol (rate ratio 0.92, p=0.31). However, time to first exacerbation was increased on mannitol (HR 0.78, p=0.022). SGRQ score was improved on mannitol compared with low-dose mannitol control (-2.4 units, p=0.046). Adverse events were similar between groups. CONCLUSIONS: Mannitol 400 mg inhaled twice daily for 12 months in patients with clinically significant bronchiectasis did not significantly reduce exacerbation rates. There were statistically significant improvements in time to first exacerbation and QOL. Mannitol therapy was safe and well tolerated. TRIAL REGISTRATION NUMBER: NCT00669331.

Inspiratory flows and volumes in subjects with cystic fibrosis using a new dry powder inhaler device.

INTRODUCTION: Drug inhalation via a dry-powder inhaler (DPI) is a convenient, time efficient alternative to nebulizers in the treatment of cystic fibrosis (CF). Efficient drug administration via DPIs depends on the device resistance and adequate (≥ 45L/min) inspiratory flows and volumes generated by individuals. Dry-powder mannitol is delivered using a RS01 breath-actuated device developed by Plastiape, for Pharmaxis. The study aim was to determine in vivo if CF patients' inspiratory flows and volumes are adequate to use the RS01 DPI device. MATERIALS AND METHODOLOGY: An open, non-interventional study; enrolled 25 CF subjects, aged ≥ 6 years with FEV1 ≥ 30 to < 90‰ predicted. Inspiratory flows and volumes were measured when subjects inhaled in a controlled manner through the RS01 device in series with a spirometer. RESULTS: The mean inspiratory volume (IV) of CF subjects was 1.83L ± 0.97. Their achieved mean ± SD peak inspiratory flow (PIF) was 75.5 ± 27.2L/min. Twenty-three subjects (92%) achieved PIF of > 45L/min with the inhaler device; eighteen of those subjects (78%) had a baseline FEV1 of > 1L. CONCLUSION: Use of the RS01 DPI device allowed adequate inspiratory flow and volume for dispersion of dry-powder mannitol in CF patients.

Inspiratory Flows and Volumes in Subjects with Non-CF Bronchiectasis Using a New Dry Powder Inhaler Device.

INTRODUCTION: Drug inhalation via a dry-powder inhaler (DPI) is a convenient, time efficient alternative to nebulizers in the treatment of cystic fibrosis (CF) or non-CF bronchiectasis. Efficient drug administration via DPIs depends on the device resistance and adequate (≥45L/min) inspiratory flows and volumes generated by individuals. Drypowder mannitol is delivered using a RS01 breath-actuated device developed by Plastiape, for Pharmaxis. The study aim was to determine in vivo if non-CF bronchiectasis patients' inspiratory flows and volumes are adequate to use the RS01 DPI device. MATERIALS AND METHODOLOGY: An open, non-interventional study; enrolled 17 subjects with non-CF bronchiectasis, 18 to 80 years, with baseline FEV1 ≥1.0L and ≥50‰ predicted. Inspiratory flows and volumes were measured when subjects inhaled in a controlled manner through the RS01 device in series with a spirometer. RESULTS: The mean inspiratory volume (IV) of non-CF bronchiectasis subjects was 2.08 ± 0.5L and achieved a mean PIF of 78.6 ± 11.2L/min with the inhaler device. CONCLUSION: Use of the RS01 DPI device allowed adequate inspiratory flow and volume for dispersion of dry-powder mannitol in non-CF bronchiectasis patients.

Phase 3 randomized study of the efficacy and safety of inhaled dry powder mannitol for the symptomatic treatment of non-cystic fibrosis bronchiectasis.

BACKGROUND: Inhaled dry powder mannitol enhanced mucus clearance and improved quality of life over 2 weeks in non-cystic fibrosis bronchiectasis. This study's objective was to investigate the efficacy and safety of dry powder mannitol over 12 weeks. METHODS: Patients with bronchiectasis confirmed by high-resolution CT (HRCT) scan, aged 15 to 80 years, with FEV1≥50% predicted and ≥1 L participated in a randomized, placebo-controlled, double-blind study. Patients with a negative mannitol provocation test were randomized to inhale 320 mg mannitol (n=231) or placebo (n=112) bid for 12 weeks. To further assess safety, the same mannitol dose/frequency was administered to a patient subset in an open-label extension over 52 weeks. Primary end points were changes from baseline at 12 weeks in 24-h sputum weight and St. George's Respiratory Questionnaire (SGRQ) score. RESULTS: There was a significant difference of 4.3 g in terms of change in sputum weight over 12 weeks (95% CI, 1.64-7.00; P=.002) between mannitol and placebo; however, this was largely driven by a decrease in sputum weight in the placebo group. This was associated, in turn, with more antibiotic use in the placebo group (50 of 112 [45%]) than in the inhaled mannitol group (85 of 231 [37%]). There was no statistical difference between the groups (P=.304) in total SGRQ score (mannitol, -3.4 points [95% CI, -4.81 to -1.94] vs placebo, -2.1 points [95% CI, -4.12 to -0.09]). In a subgroup study (n=82), patients receiving mannitol showed less small airway mucus plugging on HRCT scan at 12 weeks compared with patients receiving placebo (P=.048). Compliance rates were high, and mannitol was well tolerated with adverse events similar to those of placebo. CONCLUSION: Because the difference in sputum weights appears to be associated with increased antibiotic use in the placebo group, a larger controlled study is now required to investigate the long-term mannitol effect on pulmonary exacerbations and antibiotic use. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT0027753; URL: www.clinicaltrials.gov.

Pooled analysis of two large randomised phase III inhaled mannitol studies in cystic fibrosis.

BACKGROUND: To evaluate safety and efficacy of inhaled mannitol treatment in subgroups of a large global CF population. METHODS: Data were pooled from two multicentre, double-blind, randomised, controlled, parallel group phase III studies in which 600 patients inhaled either mannitol (400 mg) or control (mannitol 50 mg) twice a day for 26 weeks. RESULTS: Both the mean absolute change in FEV(1) (mL) and relative change in FEV(1) by % predicted from baseline for mannitol (400 mg) versus control were statistically significant (73.42 mL, 3.56%, both p<0.001). Increases in FEV(1) were observed irrespective of rhDNase use. Significant improvements in FEV1 occurred in adults but not children (6-11) or adolescents (aged 12-17). Pulmonary exacerbation incidence was reduced by 29% (p=0.039) in the mannitol (400 mg) group. CONCLUSIONS: Sustained six-month improvements in lung function and decreased pulmonary exacerbation incidence indicate that inhaled mannitol is an important additional drug in the treatment of CF.

Long-term inhaled dry powder mannitol in cystic fibrosis: an international randomized study.

RATIONALE: New treatment strategies are needed to improve airway clearance and reduce the morbidity and the time burden associated with cystic fibrosis (CF). OBJECTIVES: To determine whether long-term treatment with inhaled mannitol, an osmotic agent, improves lung function and morbidity. METHODS: Double-blind, randomized, controlled trial of inhaled mannitol, 400 mg twice a day (n = 192, "treated" group) or 50 mg twice a day (n = 126, "control" group) for 26 weeks, followed by 26 weeks of open-label treatment. MEASUREMENTS AND MAIN RESULTS: The primary endpoint was absolute change in FEV(1) from baseline in treated versus control groups, averaged over the study period. Secondary endpoints included other spirometric measurements, pulmonary exacerbations, and hospitalization. Clinical, microbiologic, and laboratory safety were assessed. The treated group had a mean improvement in FEV(1) of 105 ml (8.2% above baseline). The treated group had a relative improvement in FEV(1) of 3.75% (P = 0.029) versus the control group. Adverse events and sputum microbiology were similar in both treatment groups. Exacerbation rates were low, but there were fewer in the treated group (hazard ratio, 0.74; 95% confidence interval, 0.42-1.32; P = 0.31), although this was not statistically significant. In the 26-week open-label extension study, FEV(1) was maintained in the original treated group, and improved in the original control group to the same degree. CONCLUSIONS: Inhaled mannitol, 400 mg twice a day, resulted in improved lung function over 26 weeks, which was sustained after an additional 26 weeks of treatment. The safety profile was also acceptable, demonstrating the potential role for this chronic therapy for CF. Clinical trial registered with www.clinicaltrials.gov (NCT 00630812).

Inhaled mannitol in patients with cystic fibrosis: A randomised open-label dose response trial.

BACKGROUND: Cystic fibrosis (CF) is characterised by impaired mucociliary clearance (MCC), chronic inflammation and infection, and progressively deteriorating lung function. Inhaled mannitol (Bronchitol) has been shown to increase MCC and cough clearance and FEV(1) in CF patients, contributing to better lung hygiene and consequently a slower decline in lung function. This study was designed to determine the dose relationship of mannitol treatment and improvement in FEV(1) and FVC as well as safety. METHODS: This was a randomised, open-label, crossover, dose response study. Following a 2-week treatment with mannitol 400mg b.i.d., 48 CF patients with a mean (SD) FEV(1) % predicted of 64 (13.2), received a further 3 treatments with 40mg, 120mg or 240mg b.i.d. for 2weeks each, in random order. RESULTS: The study demonstrated a dose dependent increase in FEV(1) and FVC. The 400mg dose showed the greatest improvement and the 40mg dose had no discernible effect. The mean percent change in FEV(1) was -1.57%, 3.61%, 3.87% and 8.75% respectively for the 40mg, 120mg, 240mg and 400mg treatments. There was a statistically significant change in FEV(1) for 400mg compared to 40mg (p<0.0001) but the difference with 120mg and 240mg did not reach significance. The mean % change in FVC was -0.90, 1.74, 3.07 and 8.14, for the 40mg, 120mg, 240mg and 400mg treatment arms, with p=0.0001, p=0.0037 and p=0.0304 respectively when compared to 400mg. The highest tested dose of 400mg had a similar safety profile to the other doses tested. The change in FEV(1) and FVC by dose in the paediatric age group (<18years) was similar to the results in the adult population. CONCLUSION: Based on these results the 400mg b.i.d. dose has been further studied in phase III trials.

Inhaled mannitol improves the hydration and surface properties of sputum in patients with cystic fibrosis.

BACKGROUND: The airway mucus in patients with cystic fibrosis (CF) is dehydrated and adhesive and accumulates in the airways, resulting in chronic inflammation, infection, and progressive loss of lung function. Inhaled mannitol improves mucus clearance and, when administered over 2 weeks, it improves lung function in CF (Jaques et al. Chest. 2008;133(6):1388-1396). The changes in the physical properties of sputum after a 2-week treatment with mannitol were investigated in the same subjects with CF. METHODS: Sputum was collected before and at the end of the 2-week treatment period from 28 subjects with CF who participated in the double-blind crossover study. Mannitol or placebo 420 mg bid was inhaled over 2 weeks. The solids content, surface tension, contact angle, and viscoelasticity were measured. RESULTS: Two-week treatment with mannitol reduced the solids from 7.3% +/- 3.0% to 5.7% +/- 3.0% (P = .012), surface tension from 83.1 +/- 7.2 to 78.6 +/- 8.0 mN/m (P < .039), and contact angle from 52.4 +/- 7.7 to 47.9 +/- 7.3 degrees. There was no significant change in the viscoelastic properties of sputum (P > .1). Placebo treatment had no significant effect on the sputum properties. The change in solids content correlated with the change in both FEV(1) (r = -0.78, P = .004) and forced expiratory flow in the middle half of the FVC (r = -0.80, P = .003), and the percentage change in surface tension and contact angle correlated with the percentage change in the FEV(1) (r = -0.73, P = .012 and r = -0.63, P = .03, respectively) in these subjects. CONCLUSION: Treatment with inhaled mannitol over 2 weeks improved the hydration and surface properties of sputum in patients with CF. This effect was sustained and correlated with airway function changes. TRIAL REGISTRATION: clinicaltrials.gov; Identifier: NCT00455130.

Comparison of mannitol and methacholine to predict exercise-induced bronchoconstriction and a clinical diagnosis of asthma.

BACKGROUND: Asthma can be difficult to diagnose, but bronchial provocation with methacholine, exercise or mannitol is helpful when used to identify bronchial hyperresponsiveness (BHR), a key feature of the disease. The utility of these tests in subjects with signs and symptoms of asthma but without a clear diagnosis has not been investigated. We investigated the sensitivity and specificity of mannitol to identify exercise-induced bronchoconstriction (EIB) as a manifestation of BHR; compared this with methacholine; and compared the sensitivity and specificity of mannitol and methacholine for a clinician diagnosis of asthma. METHODS: 509 people (6-50 yr) were enrolled, 78% were atopic, median FEV1 92.5% predicted, and a low NAEPPII asthma score of 1.2. Subjects with symptoms of seasonal allergy were excluded. BHR to exercise was defined as a > or = 10% fall in FEV1 on at least one of two tests, to methacholine a PC20 < or = 16 mg/ml and to mannitol a 15% fall in FEV1 at < or = 635 mg or a 10% fall between doses. The clinician diagnosis of asthma was made on examination, history, skin tests, questionnaire and response to exercise but they were blind to the mannitol and methacholine results. RESULTS: Mannitol and methacholine were therapeutically equivalent to identify EIB, a clinician diagnosis of asthma, and prevalence of BHR. The sensitivity/specificity of mannitol to identify EIB was 59%/65% and for methacholine it was 56%/69%. The BHR was mild. Mean EIB % fall in FEV1 in subjects positive to exercise was 19%, (SD 9.2), mannitol PD15 158 (CI:129,193) mg, and methacholine PC20 2.1(CI:1.7, 2.6) mg/ml. The prevalence of BHR was the same: for exercise (43.5%), mannitol (44.8%), and methacholine (41.6%) with a test agreement between 62 & 69%. The sensitivity and specificity for a clinician diagnosis of asthma was 56%/73% for mannitol and 51%/75% for methacholine. The sensitivity increased to 73% and 72% for mannitol and methacholine when two exercise tests were positive. CONCLUSION: In this group with normal FEV1, mild symptoms, and mild BHR, the sensitivity and specificity for both mannitol and methacholine to identify EIB and a clinician diagnosis of asthma were equivalent, but lower than previously documented in well-defined populations. TRIAL REGISTRATION: This was a multi-center trial comprising 25 sites across the United States of America.

Inhaled mannitol improves lung function in cystic fibrosis.

BACKGROUND: The airways in patients with cystic fibrosis (CF) are characterized by the accumulation of tenacious, dehydrated mucus that is a precursor for chronic infection, inflammation, and tissue destruction. The clearance of mucus is an integral component of daily therapy. Inhaled mannitol is an osmotic agent that increases the water content of the airway surface liquid, and improves the clearance of mucus with the potential to improve lung function and respiratory health. To this end, this study examined the efficacy and safety of therapy with inhaled mannitol over a 2-week period. METHODS: This was a randomized, double-blind, placebo-controlled, crossover study. Thirty-nine subjects with mild-to-moderate CF lung disease inhaled 420 mg of mannitol or placebo twice daily for 2 weeks. Following a 2-week washout period, subjects were entered in the reciprocal treatment arm. Lung function, respiratory symptoms, quality of life, and safety were assessed. RESULTS: Mannitol treatment increased FEV(1) from baseline by a mean of 7.0% (95% confidence interval [CI], 3.3 to 10.7) compared to placebo 0.3% (95% CI, - 3.4 to 4.0; p < 0.001). The absolute improvement with mannitol therapy was 121 mL (95% CI, 56.3 to 185.7), which was significantly more than that with placebo (0 mL; 95% CI, - 64.7 to 64.7). The forced expiratory flow in the middle half of the FVC increased by 15.5% (95% CI, - 6.5 to 24.6) compared to that with placebo (increase, 0.7%; 95% CI, - 8.3 to 9.7; p < 0.02). The safety profile of mannitol was adequate, and no serious adverse events related to treatment were observed. CONCLUSIONS: Inhaled mannitol treatment over a period of 2 weeks significantly improved lung function in patients with CF. Mannitol therapy was safe and well tolerated. TRIAL REGISTRATION: (ClinicalTrials.gov) Identifier: NCT00455130.

The safety and efficacy of inhaled dry powder mannitol as a bronchial provocation test for airway hyperresponsiveness: a phase 3 comparison study with hypertonic (4.5%) saline.

BACKGROUND: Inhaled mannitol is a new bronchial provocation test (BPT) developed to improve portability and standardisation of osmotic challenge testing. Osmotic challenge tests have an advantage over the traditional methods of measuring airway hyperresponsiveness using methacholine as they demonstrate higher specificity to identify asthma and thus the need for treatment with inhaled corticosteroids (ICS). The safety and the efficacy of mannitol (M) as a BPT to measure airway hyperresponsiveness were compared to hypertonic (4.5%) saline (HS) in people both with and without signs and symptoms of asthma. METHODS: A phase III, multi-centre, open label, operator-blinded, crossover design, randomised trial, with follow-up. Asthmatics and non-asthmatics (6-83 yr) were recruited and 592 subjects completed the study. Mannitol was delivered using a low resistance dry powder inhaler and HS was delivered using an ultrasonic nebuliser. The FEV1 was measured 60 seconds after each dose of mannitol (5,10,20,40,80,160,160,160 mg) and after each exposure to HS (0.5,1.0,2.0,4.0,8.0 minutes). A 15% fall in FEV1 defined a positive test. Adverse events were monitored and diaries kept for 7 days following the tests. RESULTS: Mean pre-test FEV1 (mean +/- SD) was 95.5 +/- 14% predicted. 296 were positive to mannitol (M+) and 322 positive to HS (HS+). A post study physician conducted clinical assessment identified 82.3% asthmatic (44% classified mild) and 17.7% non-asthmatic. Of those M+, 70.1% were taking ICS and of those mannitol negative (M-), 81.1 % were taking ICS. The % fall in FEV1 for mannitol in asthmatics was 21.0% +/- 5.7 and for the non-asthmatics, 5.5% +/- 4.8. The median PD15 M was 148 mg and PD15 HS 6.2 ml. The sensitivity of M to identify HS+ was 80.7% and the specificity 86.7%. The sensitivity of M compared with the clinical assessment was 59.8% and specificity 95.2% and increased to 88.7% and 95.0% respectively when the M- subjects taking ICS were excluded. Cough was common during testing. There were no serious adverse events. The diarised events were similar for mannitol and HS, the most common being headache (17.2%M, 19%HS), pharyngolaryngeal pain (5.1%M, 3%HS), nausea (4.3%M, 3%HS), and cough (2.2%M, 2.4%HS). CONCLUSION: The efficacy and safety of mannitol was demonstrated in non-asthmatic and clinically diagnosed asthmatic adults and children.

Autoimmune diabetes in the NOD mouse: an essential role of Fas-FasL signaling in beta cell apoptosis.

Despite evidence that both Fas and FasL can be expressed in pancreatic islets, there has been considerable controversy regarding the potential role of Fas signaling in autoimmune beta cell death. Using the HIPFasL model, we have been able to demonstrate that, in the presence of an inflammatory infiltrate, FasL-expressing beta cells are exquisitely sensitive to Fas-mediated apoptosis and that this can be blocked by preventing FasL-Fas interaction. This points to a highly important role of Fas-FasL interaction in autoimmune beta cell death.

Beta cell MHC class I is a late requirement for diabetes.

Type 1 diabetes occurs as a result of an autoimmune attack on the insulin-producing beta cells. Although CD8 T cells have been implicated both early and late in this process, the requirement for direct interaction between these cells and MHC class I on the beta cells has not been demonstrated. By using nonobese diabetic mice lacking beta cell class I expression, we show that both initiation and progression of insulitis proceeds unperturbed. However, without beta cell class I expression, the vast majority of these mice do not develop hyperglycemia. These findings demonstrate that a direct interaction between CD8 T cells and beta cells is not required for initiation or early disease progression. The requirement for class I on beta cells is a relatively late checkpoint in the development of diabetes.

Mechanisms of accelerated immune-mediated diabetes resulting from islet beta cell expression of a Fas ligand transgene.

Nonobese diabetic (NOD) mice transgenic for Fas ligand (FasL) on islet beta cells (HIPFasL mice) exhibit an accelerated diabetes distinct from the normal autoimmune diabetes of NOD mice. This study was undertaken to define the mechanism underlying accelerated diabetes development in HIPFasL mice. It was found that diabetes in HIPFasL mice is dependent on the NOD genetic background, as HIPFasL does not cause diabetes when crossed into other mice strains and is lymphocyte dependent, as it does not develop in HIPFasL(SCID) mice. Diabetes development in NOD(SCID) recipients of diabetic HIPFasL splenocytes is slower than when using splenocytes from diabetic NOD mice. Beta cells from HIPFasL mice are more susceptible to cytokine-induced apoptosis than wild-type NOD beta cells, and this can be blocked with anti-FasL Ab. HIPFasL islets are more rapidly destroyed than wild-type islets when transplanted into nondiabetic NOD mice. This confirms that FasL(+) islets do not obtain immune privilege, and instead NOD beta cells constitutively expressing FasL are more susceptible to apoptosis induced by Fas-FasL interaction. These findings are consistent with the accelerated diabetes of young HIPFasL mice being a different disease process from the autoimmune diabetes of wild-type NOD mice. The data support a mechanism by which cytokines produced by the insulitis lesion mediate up-regulation of beta cell Fas expression, resulting in suicide or fratricide of HIPFasL beta cells that overexpress FasL.