Microglial diversity along the hippocampal longitudinal axis impacts synaptic plasticity in adult male mice under homeostatic conditions

The hippocampus is a plastic brain area that shows functional segregation along its longitudinal axis, reflected by a higher level of long-term potentiation (LTP) in the CA1 region of the dorsal hippocampus (DH) compared to the ventral hippocampus (VH), but the mechanisms underlying this difference remain elusive. Numerous studies have highlighted the importance of microglia-neuronal communication in modulating synaptic transmission and hippocampal plasticity, although its role in physiological contexts is still largely unknown. We characterized in depth the features of microglia in the two hippocampal poles and investigated their contribution to CA1 plasticity under physiological conditions. We unveiled the influence of microglia in differentially modulating the amplitude of LTP in the DH and VH, showing that minocycline or PLX5622 treatment reduced LTP amplitude in the DH, while increasing it in the VH. This was recapitulated in Cx3cr1 knockout mice, indicating that microglia have a key role in setting the conditions for plasticity processes in a region-specific manner, and that the CX3CL1-CX3CR1 pathway is a key element in determining the basal level of CA1 LTP in the two regions. The observed LTP differences at the two poles were associated with transcriptional changes in the expression of genes encoding for Il-1, Tnf-α, Il-6, and Bdnf, essential players of neuronal plasticity. Furthermore, microglia in the CA1 SR region showed an increase in soma and a more extensive arborization, an increased prevalence of immature lysosomes accompanied by an elevation in mRNA expression of phagocytic markers Mertk and Cd68 and a surge in the expression of microglial outward K⁺ currents in the VH compared to DH, suggesting a distinct basal phenotypic state of microglia across the two hippocampal poles. Overall, we characterized the molecular, morphological, ultrastructural, and functional profile of microglia at the two poles, suggesting that modifications in hippocampal subregions related to different microglial statuses can contribute to dissect the phenotypical aspects of many diseases in which microglia are known to be involved.

Vortioxetine Prevents Lipopolysaccharide-Induced Memory Impairment Without Inhibiting the Initial Inflammatory Cascade

Vortioxetine is a novel multimodal antidepressant that modulates a wide range of neurotransmitters throughout the brain. Preclinical and clinical studies have shown that vortioxetine exerts positive effects on different cognitive domains and neuroprotective effects. Considering the key role of microglial cells in brain plasticity and cognition, we aimed at investigating the effects of pretreatment with vortioxetine in modulating behavioral and molecular effects induced by an immune challenge: peripheral injection of lipopolysaccharide (LPS). To this purpose, C57BL/6J male mice were first exposed to a 28-day standard diet or vortioxetine-enriched diet, which was followed by an acute immune challenge with LPS. Sickness symptoms and depressive-like behaviors (anhedonia and memory impairment) were tested 6 and 24 h after exposure to LPS, respectively. Moreover, the expressions of markers of immune activation and M1/M2 markers of microglia polarization were measured in the dorsal and ventral parts of the hippocampus. The pretreatment with vortioxetine did not affect both LPS-induced sickness behavior and anhedonia but prevented the deficit in the recognition memory induced by the immune challenge. At the transcriptional level, chronic exposure to vortioxetine did not prevent LPS-induced upregulation of proinflammatory cytokines 6 h after the immune challenge but rather seemed to potentiate the immune response to the challenge also by affecting the levels of expression of markers of microglia M1 phenotype, like cluster of differentiation (CD)14 and CD86, in an area-dependent manner. However, at the same time point, LPS injection significantly increased the expression of the M2 polarization inducer, interleukin 4, only in the hippocampus of animals chronically exposed to vortioxetine. These results demonstrate that a chronic administration of vortioxetine specifically prevents LPS-induced memory impairment, without affecting acute sickness behavior and anhedonia, and suggest that hippocampal microglia may represent a cellular target of this novel antidepressant medication. Moreover, we provide a useful model to further explore the molecular mechanisms specifically underlying cognitive impairments following an immune challenge.

Lymnaea stagnalis as model for translational neuroscience research: From pond to bench

The purpose of this review is to illustrate how a reductionistic, but sophisticated, approach based on the use of a simple model system such as the pond snail Lymnaea stagnalis (L. stagnalis), might be useful to address fundamental questions in learning and memory. L. stagnalis, as a model, provides an interesting platform to investigate the dialog between the synapse and the nucleus and vice versa during memory and learning. More importantly, the "molecular actors" of the memory dialogue are well-conserved both across phylogenetic groups and learning paradigms, involving single- or multi-trials, aversion or reward, operant or classical conditioning. At the same time, this model could help to study how, where and when the memory dialog is impaired in stressful conditions and during aging and neurodegeneration in humans and thus offers new insights and targets in order to develop innovative therapies and technology for the treatment of a range of neurological and neurodegenerative disorders.

Modulation of neuroplasticity-related targets following stress-induced acute escape deficit

Understanding resilience is a major challenge to improve current pharmacological therapies aimed at complementing psychological-based approaches of stress-related disorders. In particular, resilience is a multi-factorial construct where the complex network of molecular events that drive the process still needs to be resolved. Here, we exploit the acute escape deficit model, an animal model based on exposure to acute unavoidable stress followed by an escape test, to define vulnerable and resilient phenotypes in rats. Hippocampus and prefrontal cortex (PFC), two of the brain areas most involved in the stress response, were analysed for gene expression at two different time points (3 and 24 h) after the escape test. Total Brain-Derived Neurotrophic Factor (BDNF) was highly responsive in the PFC at 24-h after the escape test, while expression of BDNF transcript IV increased in the hippocampus of resistant animals 3 h post-test. Expression of memory enhancers like Neuronal PAS Domain Protein 4 (Npas4) and Activity-regulated cytoskeleton-associated protein (Arc) decreased in a time- and region-dependent fashion in both behavioural phenotypes. Also, the memory inhibitor Protein Phosphatase 1 (Ppp1ca) was increased in the hippocampus of resilient rats at 3 h post-test. Given the importance of neurotrophic factors and synaptic plasticity-related genes for the development of appropriate coping strategies, our data contribute to an additional step forward in the comprehension of the psychobiology of stress and resiliency.

Early postnatal chronic inflammation produces long-term changes in pain behavior and N-methyl-D-aspartate receptor subtype gene expression in the central nervous system of adult mice

The objective of this study was to test whether postnatal chronic inflammation resulted in altered reactivity to pain later in life when reexposed to the same inflammatory agent and whether this alteration correlated with brain-region-specific patterns of N-methyl-D-aspartate (NMDA) receptor subtype gene expression. Neonatal mouse pups received a single injection of complete Freund's adjuvant (CFA) or saline into the left hind paw on postnatal day 1 or 14. At 12 weeks of age, both neonatal CFA- and saline-treated animals received a unilateral injection of CFA in the left hind paw. Adult behavioral responsiveness of the left paw to a radiant heat source was determined in mice treated neonatally with saline or CFA before and after receiving CFA as adults. Twenty-four hours later, brains were dissected and NMDA receptor subunit gene expression was determined in four different brain areas by using an RNase protection assay. The results indicated that NMDA receptor subtype gene expression in adult mice exposed to persistent neonatal peripheral inflammation was brain region specific and that NMDA gene expression and pain reactivity differed according to the day of neonatal CFA exposure. Similarly, adult behavioral responsiveness to a noxious radiant heat source differed according to the age of neonatal exposure to CFA. The data suggest a possible molecular basis for the hypothesis that chronic persistent inflammation experienced early during development may permanently alter the future behavior and the sensitivity to pain later in life, especially in response to subsequent or recurrent inflammatory events.

The modulation of intracellular glutathione level modulates the mitochondrial response in proliferating rat splenocytes

We have investigated the effect of intracellular reduced glutathione (GSH) levels on the mitochondrial parameters of proliferating rat splenocytes. The intracellular GSH content of the cells was altered by continuous culture with buthionine-S, R-sulfoximine (BSO), a specific inhibitor of GSH synthesis. BSO decreased the GSH levels, inhibited DNA synthesis and caused depolarization of mitochondria in 52% of cells stimulated to proliferate for 72 h. These data support the proposition that GSH influences the lymphocyte proliferation at more than one site, one of which is the energy producing machinery.

Detection of levodopa, dopamine and its metabolites in rat striatum dialysates following peripheral administration of l-DOPA prodrugs by mean of HPLC–EC

A high performance liquid chromatography (HPLC) method was developed to detected simultaneously L-dihydroxyphenylalanine (L-DOPA), dopamine (DA), dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in rat striatum dilaysates following oral administration of L-DOPA or its prodrugs. The chromatographic system uses a reversed-phase C18 column with electrochemical detection at +0.30 V. Mobile phase consisted of 0.05 M citric acid, sodium EDTA 50 microM, sodium octylsulphonate 0.4 nM at pH of 2.9 and 8% methanol (v/v) at a flow rate of 1 ml/min. The calibration curves were linear over the concentration range of 10nm to 100 microM and the lower limits of detections were 125 fmol for L-DOPA, 50 fmol for DOPAC, 250 fmol for DA and 150 fmol for HVA at signal noise to ratio of 3. The repeatability (or intra-day precision), expressed by the relative standard deviation, were better than 4%. The construction of microdialysis probes has been described. The in vitro relative recoveries of each microdialysis probe were evaluated and the results show that they are similar and reproducible for all the analytes with CVs from 1 to 4%. The HPLC-EC method was applied to detect the extracellular levels of L-DOPA, DA, DOPAC and HVA in the striatum dialysates of freely moving rats after oral administration of six new potential L-DOPA prodrugs.

Combined effects of cyclosporin and nifedipine on gingival overgrowth in rats is not age dependent

BACKGROUND

Cyclosporin A and nifedipine cause gingival overgrowth in rat, and the combined use of these drugs increases the overgrowth severity.

OBJECTIVE

The purpose of this study was to compare gingival overgrowth of rats of differents ages treated with cyclosporin A and nifedipine alone or given concurrently.

MATERIALS AND METHODS

Rats 15, 30, 60 and 90 d old were treated with 10 mg/kg body weight of cyclosporin A and/or 50 mg/kg body weight of nifedipine in the chow.

RESULTS

Young rats showed evident gingival overgrowth with nifedipine, cyclosporin A, and cyclosporin A and nifedipine given concurrently. Adult rats did not show significant gingival alterations when treated with cyclosporin A and nifedipine alone. Nevertheless evident gingival overgrowth with alterations of the epithelium and connective tissue were observed when treated simultaneously with cyclosporin A and nifedipine.

CONCLUSION

These results suggest that the combined effects of cyclosporin A and nifedipine on gingival overgrowth in rat is not age dependent.

Onychomycosis caused by Scytalidium dimidiatum. Report of two cases. Review of the taxonomy of the synanamorph and anamorph forms of this coelomycete

The authors report two cases of onychomycosis in the dystrophic form, one of them involving an HIV-positive patient, provoked by Scytalidium dimidiatum, previously called Scytalidium lignicola. The subject is reviewed from the taxonomic viewpoint, considering the anamorph Hendersonula toruloidea as a synonym of Nattrassia mangiferae, and having Scytalidium dimidiatum as the major synanamorph. According to many mycologists, Scytalidium hyalinum may be a separate species or a hyaline mutant of Scytalidium dimidiatum. Scytalidium lignicola Pesante 1957 was considered to be the type-species of the genus by ELLIS (1971)13 and later to be a "conidial state" of Hendersonula toruloidea by the same author, today known as Nattrassia mangiferae. The microorganism lives only on the roots of certain plants (mainly Platanus and Pinus). It produces pycnidia and is not considered to be a pathogen, although it is considered as a possible emerging agent capable of provoking opportunistic fungal lesions. The importance of this topic as one of the most outstanding in fungal taxonomy, so likely to be modified over time, as well as its interest in the field of dermatologic mycology, are emphasized.

The impairment of mitochondrial membrane potential and mass in proliferating lymphocytes from vitamin E deficient animals is recovered by glutathione

The time-dependent changes of mitochondrial membrane potential and mass have been investigated on splenocytes from control and vit. E deficient rats, stimulated to proliferate with Concanavalin A, in the presence and absence of reduced glutathione (GSH, 5 mM). Rhodamine-123 (Rh-123) and nonyl acridine orange (NAO) were used as specific probes to monitor the membrane potential and mass of mitochondria, respectively, by means of flow cytometry. Rh-123 uptake was high in an increasing number of cells from normally fed animals during the three-day culture period. On the contrary, splenocytes from vitamin E deficient rats showed a biphasic pattern. The number of cells showing a high uptake of Rh-123 increased after 24 hrs. from mitogenic stimulation, then it decreased at the other two time points considered. In parallel, a continuous increase of the number of cells with depolarized organelles (up to 60% by 72 hrs.) has been observed in vit. E deficiency. This impairment was fully prevented by GSH supplementation to the culture medium. In the presence of the thiol, about 80-85% of cells showed activated mitochondria, whereas the number of splenocytes with depolarized organelles did not exceed 17%, irrespective of the diet applied to the animals. The same pattern was observed considering the changes of mitochondrial mass, measured using NAO as a probe. Present results support that GSH may substitute vitamin E in protecting mitochondria from peroxidative damage.

[Osteochondrodysplasia: nosologic assessment and report of 6 clinical cases]

Osteochondrodysplasias represent an important group of disease affecting cartilage and/or bone. The clinical evidence of disarmoniuous low stature, of a disproportion between trunk and limbs length, of a big skull can suggest this diagnosis and the necessity to carry out all the instrumental investigations. The diagnostic suspect can be placed, some time, already in the neonatal period. The complexity of problems regarding the osteochondrodysplasias bearer child and his family requires a multidisciplinary approach. The Authors present a personal experience of six cases of osteochondrodysplasias observed in a period of fifteen years.