Bead discrimination training in chicks sets in motion a tightly timed series of biochemical events, including glutamate release, increase in forebrain level of glutamate and utilization of glycogen and glucose. Inhibition of glycogen breakdown by the glycogen phosphorylase inhibitor 1,4-dideoxy-1,4-imino-D-arabinitol (DAB) around the time of training abolishes the increase in glutamate 5 min posttraining in the left hemisphere, in spite of uninhibited glucose metabolism. It also reduces the contents of glutamate, glutamine, and aspartate in the right hemisphere. Behavioral evidence supports the conclusion that glucose breakdown serves to provide energy, whereas glycogen acts as a substrate for glutamate, glutamine, and aspartate formation, requiring both pyruvate dehydrogenation to acetyl coenzyme A and pyruvate carboxylation in astrocytes. Inhibition of memory consolidation caused by DAB or 2-deoxyglucose (2-DG), an inhibitor of glucose phosphorylation without effect on glycogen metabolism, was challenged by intracerebral administration of acetate, aspartate, glutamine, lactate or glucose. DAB-mediated memory inhibition was successfully challenged by administration at 0 or 20 min posttraining of acetate (an astrocyte-specific acetyl CoA precursor) together with aspartate, substituting for pyruvate carboxylation, or of glutamine at 0-2.5 or 30 min posttraining. 2-DG-mediated memory impairment was not challenged by acetate with or without aspartate at 0 time but was challenged by acetate without aspartate at 20 min. Lactate, a substrate for both dehydrogenation and pyruvate carboxylation challenged both DAB and 2-DG. Doses of DAB and 2-DG which, on their own were subeffective, were not additive, further supporting the existence of one pathway using glucose and another using glycogen.

BACKGROUND AND PURPOSE Lymphangioleiomyomatosis (LAM) is characterized by the abnormal growth of smooth muscle‐like cells (LAM cells) and cystic destruction of the lung parenchyma. LAM cell‐derived matrix metalloproteinases (MMPs) are thought to play a prominent role in the tissue destruction. The aim of this study was to determine whether doxycycline, a known MMP inhibitor, can inhibit LAM cell proliferation or mitochondrial function and/or modulate MMPs and their tissue inhibitors (TIMPs). EXPERIMENTAL APPROACH Wild‐type and tuberous sclerosis complex‐2 (TSC2)‐null mouse embryonic fibroblasts (MEFs) were cultured in DMEM containing 10% fetal bovine serum (FBS). Human LAM cells were derived from the lungs of LAM patients and airway smooth muscle cells from control subjects. Cells were stimulated with FBS with or without doxycycline for up to 9 days. Proliferation was assessed by manual cell counts and MTT assay, MMP production by zymography and ELISA, and TIMP production using elisa. KEY RESULTS Doxycycline did not change FBS‐induced proliferation in MEFs or human cells. However, doxycycline did reduce metabolic activity of both wild‐type and TSC2‐null MEFs and LAM cells, but had no effect on control cells. Furthermore, doxycycline reduced MMP‐2 from MEFs and decreased active‐MMP‐2 from LAM cells but had no effect on TIMP‐1 and TIMP‐2 from human LAM cells. CONCLUSIONS AND IMPLICATIONS Doxycycline decreased MMP levels and cell metabolic activity, which raises the possibility of therapeutic efficacy in LAM.

SummaryTransient procoagulant states resulting in failure of recanalization or rethrombosis of the reperfused artery during thrombolytic therapy might be due to an inhibitory effect of plasmin on the anticoagulant properties of protein C. We therefore studied the effect of plasmin on protein C (PC) and activated protein C (APC) using purified human proteins.Incubation of 70 nM purified human PC with 40-400 nM human plasmin resulted in rapid activation and subsequent inactivation of PC as measured by amidolytic and anticoagulant assays. The rates of activation and inactivation were dependent on the concentration of plasmin. Lower concentrations of plasmin resulted in higher peaks of generated APC and more sustained activity, while at higher concentrations, both activation and inactivation were more rapid. Anticoagulant activity appeared more sensitive to inactivation by plasmin than amidolytic activity; e. g., while amidolytic activity reached a maximum of 13.8 nM in 6 min and declined to approximately 6 nM after 30 min, anticoagulant activity reached its maximum of only 1.4 nM within 30 s and completely disappeared within 90 s.Plasmin rapidly destroyed both the anticoagulant and amidolytic activity of purified APC, with second order rate constants of 2.8 × 105 M−1 s−1 and 1.2 × 104 M−1 −1, respectively, for 70 nM APC. The rates of activation and subsequent inactivation were slowed by the presence of CaCl2. The second order rate constant of inactivation of APC amidolytic activity decreased to 6.6 × 103 M−1 s−1 in the presence of 5 mM CaCl2. Proteolytic degradation of both PC and APC corresponding to the loss of amidolytic activity was demonstrated on SDS-PAGE using 125I-labelled proteins. When normal human plasma was incubated with plasmin or streptokinase a substantial loss of PC anticoagulant activity was observed.These results in vitro suggest that plasmin modulates the anticoagulant properties of protein C in a way that might be of relevance for the success of fibrinolytic therapy.

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