Perceptual learning deficits mediated by somatostatin releasing inhibitory interneurons of olfactory bulb in an early life stress mouse model.

Early life adversity (ELA) causes aberrant functioning of neural circuits affecting the health of an individual. While ELA-induced behavioural disorders resulting from sensory and cognitive disabilities can be assessed clinically, the neural mechanisms need to be probed using animal models by employing multi-pronged experimental approaches. As ELA can alter sensory perception, we investigated the effect of early weaning on murine olfaction. By implementing go/no-go odour discrimination paradigm, we observed olfactory learning and memory impairments in early life stressed (ELS) male mice. As olfactory bulb (OB) circuitry plays a critical role in odour learning, we studied the plausible changes in the OB of ELS mice. Lowered c-Fos activity in the external plexiform layer and a reduction in the number of dendritic processes of somatostatin-releasing, GABAergic interneurons (SOM-INs) in the ELS mice led us to hypothesise the underlying circuit. We recorded reduced synaptic inhibitory feedback on mitral/tufted (M/T) cells, in the OB slices from ELS mice, explaining the learning deficiency caused by compromised refinement of OB output. The reduction in synaptic inhibition was nullified by the photo-activation of ChR2-expressing SOM-INs in ELS mice. The role of SOM-INs was revealed by learning-dependent refinement of Ca2+dynamics quantified by GCaMP6f signals, which was absent in ELS mice. Further, the causal role of SOM-INs involving circuitry was investigated by optogenetic modulation during the odour discrimination learning. Photo-activating these neurons rescued the ELA-induced learning deficits. Conversely, photo-inhibition caused learning deficiency in control animals, while it completely abolished the learning in ELS mice, confirming the adverse effects mediated by SOM-INs. Our results thus establish the role of specific inhibitory circuit in pre-cortical sensory area in orchestrating ELA-dependent changes.

Río-Hortega's drawings revisited with fluorescent protein defines a cytoplasm-filled channel system of CNS myelin.

A century ago this year, Pío del Río-Hortega (1921) coined the term 'oligodendroglia' for the 'interfascicular glia' with very few processes, launching an extensive discovery effort on his new cell type. One hundred years later, we review his original contributions to our understanding of the system of cytoplasmic channels within myelin in the context of what we observe today using light and electron microscopy of genetically encoded fluorescent reporters and immunostaining. We use the term myelinic channel system to describe the cytoplasm-delimited spaces associated with myelin; being the paranodal loops, inner and outer tongues, cytoplasm-filled spaces through compact myelin and further complex motifs associated to the sheath. Using a central nervous system myelinating cell culture model that contains all major neural cell types and produces compact myelin, we find that td-tomato fluorescent protein delineates the myelinic channel system in a manner reminiscent of the drawings of adult white matter by Río-Hortega, despite that he questioned whether some cytoplasmic figures he observed represented artefact. Together, these data lead us to propose a slightly revised model of the 'unrolled' sheath. Further, we show that the myelinic channel system, while relatively stable, can undergo subtle dynamic shape changes over days. Importantly, we capture an under-appreciated complexity of the myelinic channel system in mature myelin sheaths.

Targeted prodrug treatment of HER-2-positive breast tumor cells using trastuzumab and paclitaxel linked by A-Z-CINN Linker.

Targeting drugs for delivery and release has the potential to increase the efficacy of treatment. A bifunctional linker, A-Z-CINN Linker was used to create a targeted prodrug, A-Z-CINN 310. A-Z-CINN Linker links to a potent chemotherapeutic agent, paclitaxel, via an energy-reversible ester bond and also binds a targeting agent, the monoclonal antibody trastuzumab (Herceptin). This study demonstrates the effectiveness of a single-treatment use of A-Z-CINN 310 in decreasing tumor volume and tumor cell density of human HER-2-positive BT-474 mammary tumor cells implanted in scid mice, compared to treatment with simultaneously administered trastuzumab and paclitaxel and with saline control. After treatment with A-Z-CINN 310, some mice received light exposure at 6 h for 5 min adjacent to the tumor to cause light-accelerated release of paclitaxel. Changes in tumor volume were measured for 28 days following treatment; changes in histology were measured at 31 days. Animals treated with A-Z-CINN 310, then light, showed dose-dependent decreases in tumor volume and tumor cell density which were more rapid and extensive than those seen with A-Z-CINN 310 without light or a 10-fold higher concentration of co-administered trastuzumab plus paclitaxel. This suggests that targeted delivery of paclitaxel using A-Z-CINN 310 kills tumor cells by localized release of paclitaxel at the tumor site, which can be accelerated by light treatment. These results indicate that a targeted prodrug therapy containing trastuzumab as the targeting agent and A-Z-CINN-paclitaxel as the prodrug results in a conjugate that is more effective in killing tumor cells than equivalent concentrations of co-administered trastuzumab and paclitaxel. Targeting of a drug can reduce the dose needed for effective therapy and can increase local bioavailability. This makes targeted therapy using an A-Z-CINN prodrug delivery system feasible for treating both primary and metastatic tumors.