Biology subjects

Diniz, D. M.

Publications and source records attributed to Diniz, D. M..

3 recordsLinked to original sources

bioRxiv2020

BDNF Overexpression in the Prelimbic Cortex Does Not Reduce Anxiety- and Depression-like Behavior in Serotonin Knockout Rats

Depressive disorders are one of the leading causes of non-fatal health loss in the last decade. Adding to the burden, the available treatments not always properly work for some individuals. There is, therefore, a constant effort from clinical and preclinical studies to bring forward a better understanding of the disease and look for novel alternative therapies. Two target systems very well explored are the serotonin and the brain-derived neurotrophic factor (BDNF) systems. Selective serotonin reuptake inhibitors (SSRIs), a commonly used class of antidepressants, target the serotonin transporter (SERT) and increase serotonin levels, which in turn also leads to an increase in BDNF. A rat model lacking SERT (SERT knockout) has been a useful tool to study the interplay between serotonin and BDNF. SERT-/- rats present increased extracellular levels of serotonin, yet BDNF levels are decreased, especially in the prefrontal cortex (PFC) and hippocampus. The animals further display anxiety- and depression-like behavior. Therefore, BDNF might mediate the phenotype expressed by the SERT-/- rats. In this study, we sought to investigate whether overexpression of BDNF in the brain of SERT-/- rats would rescue its anxious and depressive-like behavior. Through stereotaxic surgery, SERT-/- and wild-type (WT) rats received BDNF or GFP lentivirus microinfusions into the prelimbic cortex subregion of the mPFC and were submitted to the sucrose consumption, open field test, and forced swim tests. Additionally, we measured hypothalamus-pituitary-adrenal (HPA)-axis reactivity. The results revealed that SERT-/- rats presented decreased sucrose intake, decreased locomotor activity, and increased escape-oriented behavior in the forced swim test compared to WT rats. BDNF upregulation in WT rats caused alterations in the HPA-axis function, resulting in elevated basal plasma corticosterone levels and decreased plasma corticosterone upon stress. In conclusion, BDNF overexpression in the PrL, in general, did not rescue SERT-/- rats from its depression- and anxiety-like behavior, and in WT animals, it caused a malfunction in the HPA-axis.

animal behavior and cognition↗

bioRxiv2020

BDNF overexpression in the ventral hippocampus promotes antidepressant- and anxiolytic-like activity in serotonin transporter knockout rats

Brain-derived neurotrophic factor is one of the most studied proteins playing a pivotal role in neuroplasticity events and vulnerability and resilience to stress-related disorders. Most importantly, BDNF is decreased in depressive patients, and increased after antidepressant treatment. Additionally, BDNF was found to be reduced in a genetic subset of depression susceptible patients carrying the human polymorphism in the serotonin transporter promoter region (5-HTTLPR). The serotonin knockout rat (SERT-/-) is one of the animal models used to investigate the underlying molecular mechanisms behind the genetic susceptibility to depression in humans. SERT-/- rats present decreased BDNF levels, especially BDNF exon IV, in the prefrontal cortex (PFC) and ventral hippocampus (vHIP), and display anxiety- and depression-like behavior. To investigate whether upregulating BDNF in the vHIP would meliorate the phenotype of SERT-/- rats, we overexpressed BDNF locally into the rat brain by means of stereotaxic surgery and submitted the animals to behavioral challenges, including the sucrose consumption, the open field, and forced swim tests. Additionally, we measured hypothalamus-pituitary-adrenal (HPA)-axis reactivity. The results showed that lentivirus-induced BDNF IV overexpression in the vHIP of SERT-/- rats promoted higher sucrose preference and sucrose intake, on the first day of the sucrose consumption test, indicative for decreased anhedonia-like behavior. Moreover, it decreased immobility time in the forced swim test, suggesting adaptive passive coping. Additionally, BDNF upregulation increased the time spent in the center of a novel environment, implying decreased novel-induced anxiety-like behavior. Finally, it promoted a stronger decrease in plasma corticosterone levels 60 minutes after restraint stress. In conclusion, modulation of BDNF IV levels in the vHIP of SERT-/- rats led to a positive behavioral outcome placing BDNF upregulation in the vHIP as a potential candidate for the development new therapeutic approaches targeting the improvement of depressive symptoms.

animal behavior and cognition↗

bioRxiv2020

Crossing the Blood-Brain-Barrier: A bifunctional liposome for BDNF gene delivery - A Pilot Study

To achieve their therapeutic effect on the brain, molecules need to pass the blood-brain-barrier (BBB). Many pharmacological treatments of neuropathologies encounter the BBB as a barrier, hindering their effective use. Pharmaceutical nanotechnology based on optimal physicochemical features and taking advantage of naturally occurring permeability mechanisms, nanocarriers such as liposomes offer an attractive alternative to allow drug delivery across the BBB. Liposomes are spherical bilayer lipid-based nanocapsules that can load hydrophilic molecules in their inner compartment and on their outer surface can be functionally modified by peptides, antibodies and polyethyleneglycol (PEG). When composed of cationic lipids, liposomes can serve as gene delivery devices, encapsulating and protecting genetic material from degradation and promoting nonviral cell transfection. In this study, we aimed to develop a liposomal formulation to encapsulate a plasmid harbouring brain-derived neurotrophic factor (BDNF) and infuse these liposomes via the peripheral bloodstream into the brain. To this end, liposomes were tagged with PEG, transferrin, and arginine and characterized regarding their physical properties, such as particle size, zeta-potential and polydispersity index (PDI). Moreover, we selected liposomes preparations for plasmid DNA (pDNA) encapsulation and checked for loading efficiency, in vitro cell uptake, and transfection. The preliminary results from this pilot study revealed that we were able to replicate the liposomes synthesis described in literature, achieving compatible size, charge, PDI, and loading efficiency. However, we could not properly determine whether the conjugation of the surface ligands transferrin and arginine to PEG worked and whether they were attached to the surface of the liposomes. Additionally, we were not able to see transfection in SH-SY5Y cells after 24 or 48 hours of incubation with the pDNA loaded liposomes. In conclusion, we synthesized liposomes encapsulation pBDNF, however, further research will be necessary to address the complete physicochemical characterization of the liposomes. Furthermore, preclinical studies will be helpful to verify transfection efficiency, cytotoxicity, and in the future, safe delivery of BDNF through the BBB.

pharmacology and toxicology↗