ABSTRACT
Human islet isolation is associated with adverse conditions inducing apoptosis and necrosis. The aim of the present study was to assess whether antiapoptotic preconditioning can improve in vitro and posttransplant function of isolated human islets. A dose-finding study demonstrated that 200 µmol/L of the caspase-3 inhibitor Ac-DEVD-CMK was most efficient to reduce the expression of activated caspase-3 in isolated human islets exposed to severe heat shock. Ac-DEVD-CMK-pretreated or sham-treated islets were transplanted into immunocompetent or immunodeficient diabetic mice and subjected to static glucose incubation to measure insulin and proinsulin secretion. Antiapoptotic pretreatment significantly deteriorated graft function resulting in elevated nonfasting serum glucose when compared to sham-treated islets transplanted into diabetic nude mice (p < 0.01) and into immunocompetent mice (p < 0.05). Ac-DEVD-CMK pretreatment did not significantly change basal and glucose-stimulated insulin release compared to sham-treated human islets but increased the proinsulin release at high glucose concentrations (20 mM) thus reducing the insulin-to-proinsulin ratio in preconditioned islets (p < 0.05). This study demonstrates that the caspase-3 inhibitor Ac-DEVD-CMK interferes with proinsulin conversion in preconditioned islets reducing their potency to cure diabetic mice. The mechanism behind this phenomenon is unclear so far but may be related to the ketone CMK linked to the Ac-DEVD molecule. Further studies are required to identify biocompatible caspase inhibitors suitable for islet preconditioning.
Subject(s)
Caspase Inhibitors/pharmacology , Insulin/metabolism , Islets of Langerhans Transplantation/physiology , Islets of Langerhans/physiology , Proinsulin/metabolism , Transplantation Conditioning/methods , Amino Acid Chloromethyl Ketones/pharmacology , Animals , Caspase 3 , Diabetes Mellitus, Experimental/surgery , Glucose/pharmacology , Heat-Shock Proteins/biosynthesis , Hot Temperature/adverse effects , Humans , Insulin Secretion , Mice , Mice, Nude , Tissue and Organ Procurement/methods , Transplantation, Heterologous/physiologyABSTRACT
BACKGROUND: At present, the combination of docetaxel/doxorubicin/cyclophosphamide (TAC) is considered a treatment option for patients with node-positive primary breast cancer; however, treatment is associated with grade 1-4 anemia in up to 95% of patients (grade 2-4 in 36%). PATIENTS AND METHODS: We prospectively investigated the use of a primary prophylaxis with darbepoetin alfa once every 3 weeks in 35 patients receiving 6-8 cycles of TAC as neoadjuvant treatment for breast cancer. Darbepoetin alfa treatment was started on day 1 of a TAC cycle if hemoglobin (Hb) level was /= 14 g/dL. The primary aim was to prevent Hb levels 14 g/dL in 12 patients (34.3%) and in 13 cycles (5.4%). Hemoglobin level on day 21 of the last cycle was
