Amphetamine Induces Oxidative Stress, Glial Activation and Transient Angiogenesis in Prefrontal Cortex via AT1-R

Background: Amphetamine (AMPH) alters neurons, glia and microvessels, which affects neurovascular unit coupling, leading to disruption in brain functions such as attention and working memory. Oxidative stress plays a crucial role in these alterations. The angiotensin type I receptors (AT₁-R) mediate deleterious effects, such as oxidative/inflammatory responses, endothelial dysfunction, neuronal oxidative damage, alterations that overlap with those observed from AMPH exposure. Aims: The aim of this study was to evaluate the AT₁-R role in AMPH-induced oxidative stress and glial and vascular alterations in the prefrontal cortex (PFC). Furthermore, we aimed to evaluate the involvement of AT₁-R in the AMPH-induced short-term memory and working memory deficit. Methods: Male Wistar rats were repeatedly administered with the AT₁-R blocker candesartan (CAND) and AMPH. Acute oxidative stress in the PFC was evaluated immediately after the last AMPH administration by determining lipid and protein peroxidation. After 21 off-drug days, long-lasting alterations in the glia, microvessel architecture and to cognitive tasks were evaluated by GFAP, CD11b and von Willebrand immunostaining and by short-term and working memory assessment. Results: AMPH induced acute oxidative stress, long-lasting glial reactivity in the PFC and a working memory deficit that were prevented by AT₁-R blockade pretreatment. Moreover, AMPH induces transient angiogenesis in PFC via AT₁-R. AMPH did not affect short-term memory. Conclusion: Our results support the protective role of AT₁-R blockade in AMPH-induced oxidative stress, transient angiogenesis and long-lasting glial activation, preserving working memory performance.

Facile synthesis of antibiotic-functionalized gold nanoparticles for colorimetric bacterial detection

The development of quick and efficient methods for the detection of pathogenic bacteria is urgently needed for the diagnosis of infectious diseases and the control of microbiological contamination in global waterways, potable water sources and the food industry. This contribution will describe the synthesis of gold nanoparticles and their conjugation to broad spectrum, polypeptide and β-lactam antibiotics that function as both reducing agents and surface protectants (ATB@AuNP). Nanoparticle colloids examined using transmission electron microscopy are generally spherical in shape and range from 2-50 nm in size. Dynamic light scattering and infrared spectroscopy were also used to confirm encapsulation of the AuNP surface by antibiotic molecules. ATB@AuNP were then used to detect 3 common pathogenic bacterial species: Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The colour of the AuNP colloid was monitored visually and using UV-visible spectroscopy. A red shift of the UV visible absorbance and a visible colour change following introduction of each pathogen is indicative of ATB binding to the bacteria surface, ascribed to AuNP agglomeration. This work demonstrates that ATB@AuNP may be an efficient and high throughput tool for the rapid detection of common bacterial contaminants.

Rapid and effective photodynamic treatment of biofilm infections using low doses of amoxicillin-coated gold nanoparticles

Bacterial biofilm are complex microbial communities covered by a matrix of extracellular polymeric substances, which develops when a community of microorganisms irreversibly adheres to a living or inert surface. This structure is considered an important virulence factor because it is difficult to eradicate and often responsible for treatment failures. This adherent community represents one of the greatest problems in public health due to the continued emergence of conventional antibiotic-therapy resistance. Photodynamic Antimicrobial Therapy (PACT) is a therapeutic alternative and promises to be an effective treatment against multiresistant bacteria biofilm, demonstrating a broad spectrum of action. This work demonstrates the reduction in biofilms of relevant clinical isolates (as Pseudomonas aeruginosa and Staphylococcus aureus) treated with PACT using low concentrations of amoxicillin-coated gold nanoparticles (amoxi@AuNP) as a photosensitizer. Moreover, the viability reduction of 60% in S. aureus biofilms and 70% in P. aeruginosa biofilms were obtained after three hours of irradiation with white light and amoxi@AuNP. Scanning electron microscopy analysis revealed that amoxi@AuNP could penetrate and cause damage to the biofilm matrix, and interact with bacteria cells. A strong biofilm production in P. aeruginosa was observed by confocal laser scanning microscopy using acridine orange as a probe, and a markedly decrease in live bacteria was appreciated when PACT was applied. The use of amoxi@AuNP for PACT allows the viability reduction of clinical Gram positive and Gram negative biofilms. This novel strategy needs shorter irradiation times and lower concentrations of nanoparticles than other reports described. This could be attributed to two major innovations: the selectivity for the bacterial wall given by the amoxicillin and the polydispersity of size and shapes with seems to contribute to the photo-antibacterial capacity.

AT1 -R is involved in the development of long-lasting, region-dependent and oxidative stress-independent astrocyte morphological alterations induced by Ketamine

Astrocytes play an essential role in the genesis, maturation and regulation of the neurovascular unit. Multiple evidence support that astrocyte reactivity has a close relationship to neurovascular unit dysfunction, oxidative stress and inflammation, providing a suitable scenario for the development of mental disorders. Ketamine has been proposed as a single-use antidepressant treatment in major depression, and its antidepressant effects have been associated with anti-inflammatory properties. However, Ketamine long-lasting effects over the neurovascular unit components remain unclear. Angiotensin II AT₁ receptor (AT₁ -R) blockers have anti-inflammatory, antioxidant and neuroprotective effects. The present work aims to distinguish the acute and long-term Ketamine effects over astrocytes response extended to other neurovascular unit components, and the involvement of AT₁ -R, in prefrontal cortex and ventral tegmental area. Male Wistar rats were administered with AT₁ -R antagonist Candesartan/Vehicle (days 1-10) and Ketamine/Saline (days 6-10). After 14 days drug-free, at basal conditions or after Ketamine Challenge, the brains were processed for oxidative stress analysis, cresyl violet staining and immunohistochemistry for glial, neuronal activation and vascular markers. Repeated Ketamine administration induced long-lasting region-dependent astrocyte reactivity and morphological alterations, and neuroadaptative changes observed as exacerbated oxidative stress and neuronal activation, prevented by the AT₁ -R blockade. Ketamine Challenge decreased microglial and astrocyte reactivity and augmented cellular apoptosis, independently of previous treatment. Overall, AT₁ -R is involved in the development of neuroadaptative changes induced by repeated Ketamine administration but does not interfere with the acute effects supporting the potential use of AT₁ -R blockers as a Ketamine complementary therapy in mental disorders.