To address the need for novel alternatives to antibiotics, we attempted to sensitize gram-negative bacilli to innate antibacterial protagonists. We report a lipopeptide-like sequence (C10OOc12O) that inflicted outer membrane damage at a low micromolar range, whereas measurable bacterial growth inhibition in broth medium required >10-fold higher concentrations. In serum, however, C10OOc12O induced antibacterial activity in a manner suppressible by anticomplement antibodies or heat treatment and acted synergistically with exogenous lysozyme in broth and serum media. Upon subcutaneous administration, C10OOc12O exhibited high circulating levels that correlated with significant therapeutic efficacies, using either the mouse peritonitis-sepsis model or the thigh infection model. These findings are consistent with the view that, by damaging the outer membrane, C10OOc12O was able to enhance gram-negative bacilli susceptibility to antibacterial components of the immune humoral arm. Such lipopeptides may therefore be useful in fighting gram-negative bacilli threats through sensitization to endogenous and/or exogenous antibacterial proteins such as lysozyme and complements.

No abstract

IntroductionAccumulation of amyloid β in the brain is regarded as a key initiator of Alzheimer's disease pathology. Processing of the amyloid precursor protein (APP) in the amyloidogenic pathway yields neurotoxic amyloid β species. In the non-amyloidogenic pathway, APP is processed by membrane-bound ADAM10, the main α-secretase in the nervous system. Here we present a new enzymatic approach for the potential treatment of Alzheimer's disease using a soluble form of ADAM10.MethodsThe ability of the soluble ADAM10 to shed overexpressed and endogenous APP was determined with an ADAM10 knockout cell line and a human neuroblastoma cell line, respectively. We further examined its effect on amyloid β aggregation by thioflavin T fluorescence, HPLC, and confocal microscopy. Using N-terminal and C-terminal enrichment proteomic approaches, we identified soluble ADAM10 substrates. Finally, a truncated soluble ADAM10, based on the catalytic domain, was expressed in Escherichia coli for the first time, and its activity was evaluated.ResultsThe soluble enzyme hydrolyzes APP and releases the neuroprotective soluble APPα when exogenously added to cell cultures. The soluble ADAM10 inhibits the formation and aggregation of characteristic amyloid β extracellular neuronal aggregates. The proteomic investigation identified new and verified known substrates, such as VGF and N-cadherin, respectively. The truncated variant also exhibited α-secretase capacity as shown with a specific ADAM10 fluorescent substrate in addition to shedding overexpressed and endogenous APP.DiscussionOur in vitro study demonstrates that exogenous treatment with a soluble variant of ADAM10 would shift the balance toward the non-amyloidogenic pathway, thus utilizing its natural neuroprotective effect and inhibiting the main neurotoxic amyloid β species. The potential of such a treatment for Alzheimer's disease needs to be further evaluated in vivo.