Determination of the Best Concentration of Streptozotocin to Create a Diabetic Brain Using Histological Techniques

Brain-targeted Tet-1 peptide-PLGA nanoparticles for berberine delivery against STZ-induced Alzheimer's disease in a rat model: Alleviation of hippocampal synaptic dysfunction, Tau pathology, and amyloidogenesis

Alzheimer's disease (AD) is an age-related neurodegenerative disorder that causes severe dementia and memory loss. Surface functionalized poly(lactic-co-glycolic acid) nanoparticles have been reported for better transport through the blood-brain barrier for AD therapy. This study investigated the improved therapeutic potential of berberine-loaded poly(lactic-co-glycolic acid)/Tet-1 peptide nanoparticles (BBR/PLGA-Tet NPs) in a rat model of sporadic AD. BBR was loaded into the PLGA-Tet conjugate. BBR/PLGA-Tet NPs were physicochemically and morphologically characterized. AD was achieved by bilateral intracerebroventricular (ICV) injection of streptozotocin (STZ). Cognitively impaired rats were divided into STZ, STZ + BBR, STZ + BBR/PLGA-Tet NPs, and STZ + PLGA-Tet NPs groups. Cognitive improvement was assessed using the Morris Water Maze. Brain acetylcholinesterase and monoamine oxidase activities, amyloid β42 (Aβ42), and brain glycemic markers were estimated. Further, hippocampal neuroplasticity (BDNF, pCREB, and pERK/ERK), Tau pathogenesis (pGSK3β/GSK3β, Cdk5, and pTau), inflammatory, and apoptotic markers were evaluated. Finally, histopathological changes were monitored. ICV-STZ injection produces AD-like pathologies evidenced by Aβ42 deposition, Tau hyperphosphorylation, impaired insulin signaling and neuroplasticity, and neuroinflammation. BBR and BBR/PLGA-Tet NPs attenuated STZ-induced hippocampal damage, enhanced cognitive performance, and reduced Aβ42, Tau phosphorylation, and proinflammatory responses. BBR/PLGA-Tet NPs restored neuroplasticity, cholinergic, and monoaminergic function, which are critical for cognition and brain function. BBR/PLGA-Tet NPs may have superior therapeutic potential in alleviating sporadic AD than free BBR due to their bioavailability, absorption, and brain uptake.

Comparable assessment of adolescent repeated physical or psychological stress effects on adult cardiac performance in female rats

Extensive evidence highlights a robust connection between various forms of chronic stress and cardiovascular disease (CVD). In today's fast-paced world, with chronic stressors abound, CVD has emerged as a leading global cause of mortality. The intricate interplay of physical and psychological stressors triggers distinct neural networks within the brain, culminating in diverse health challenges. This study aims to discern the unique impacts of chronic physical and psychological stress on the cardiovascular system, unveiling their varying potencies in precipitating CVD. Twenty-one adolescent female rats were methodically assigned to three groups: (1) control (n = 7), (2) physical stress (n = 7), and (3) psychological stress (n = 7). Employing a two-compartment enclosure, stressors were administered to the experimental rats over five consecutive days, each session lasting 10 min. After a 1.5-month recovery period post-stress exposure, a trio of complementary techniques characterized by high specificity or high sensitivity were employed to meticulously evaluate CVD. Echocardiography and single-photon emission computed tomography (SPECT) were harnessed to scrutinize left ventricular architecture and myocardial viability, respectively. Subsequently, the rats were ethically sacrificed to facilitate heart removal, followed by immunohistochemistry staining targeting glial fibrillary acidic protein (GFAP). Rats subjected to psychological stress showed a wider range of significant cardiac issues compared to control rats. This included left ventricular hypertrophy [IVSd: 0.1968 ± 0.0163 vs. 0.1520 ± 0.0076, P < 0.05; LVPWd: 0.2877 ± 0.0333 vs. 0.1689 ± 0.0057, P < 0.01; LVPWs: 0.3180 ± 0.0382 vs. 0.2226 ± 0.0121, P < 0.05; LV-mass: 1.283 ± 0.0836 vs. 1.000 ± 0.0241, P < 0.01], myocardial ischemia [21.30% vs. 32.97%, P < 0.001], and neuroinflammation. This outcome underscores the imperative of prioritizing psychological well-being during adolescence, presenting a compelling avenue to curtail the prevalence of CVD in adulthood. Furthermore, extending such considerations to individuals grappling with CVD might prospectively enhance their overall quality of life.

Synaptic loss and gliosis in the nucleus tractus solitarii with streptozotocin-induced Alzheimer's disease

Obstructive sleep apnea is highly prevalent in Alzheimer's disease (AD). However, brainstem centers controlling respiration have received little attention in AD research, and mechanisms behind respiratory dysfunction in AD are not understood. The nucleus tractus solitarii (nTS) is an important brainstem center for respiratory control and chemoreflex function. Alterations of nTS integrity, like those shown in AD patients, likely affect neuronal processing and adequate control of breathing. We used the streptozotocin-induced rat model of AD (STZ-AD) to analyze cellular changes in the nTS that corroborate previously documented respiratory dysfunction. We used 2 common dosages of STZ (2 and 3 mg/kg STZ) for model induction and evaluated the early impact on cell populations in the nTS. The hippocampus served as control region to identify site-specific effects of STZ. There was significant atrophy in the caudal nTS of the 3 mg/kg STZ-AD group only, an area known to integrate chemoafferent information. Also, the hippocampus had significant atrophy with the highest STZ dosage tested. Both STZ-AD groups showed respiratory dysfunction along with multiple indices for astroglial and microglial activation. These changes were primarily located in the caudal and intermediate nTS. While there was no change of astrocytes in the hippocampus, microglial activation was accompanied by a reduction in synaptic density. Together, our data demonstrate that STZ-AD induces site-specific effects on all major cell types, primarily in the caudal/intermediate nTS. Both STZ dosages used in this study produced a similar outcome and can be used for future studies examining the initial symptoms of STZ-AD.

Protection of Beta Boswellic Acid against Streptozotocin-induced Alzheimer's Model by Reduction of Tau Phosphorylation Level and Enhancement of Reelin Expression

Alzheimer's disease is a growing general health concern with huge implications for individuals and society. Beta boswellic acid, a major compound of the Boswellia serrata plant, has long been used for the treatment of various inflammatory diseases. The exact mechanism of beta boswellic acid action in Alzheimer's disease pathogenesis remains unclear. In the current study, the protective effect of beta boswellic acid on streptozotocin-induced sporadic Alzheimer's disease was surveyed. Alzheimer's disease model was induced using streptozotocin followed by an assessment of the treatment effects of beta boswellic acid in the presence of streptozotocin. The prevention effect of beta boswellic acid on Alzheimer's disease induction by streptozotocin was evaluated. Behavioral activities in the treated rats were evaluated. Histological analysis was performed. Phosphorylation of tau protein at residues Ser396 and Ser404 and the expression of reelin protein were determined. Glial fibrillary acidic protein immunofluorescence staining was applied in the hippocampus regions. Our findings indicated that beta boswellic acid decreased traveled distance and escape latency in the prevention (beta boswellic acid + streptozotocin) and treatment (streptozotocin + beta boswellic acid) groups compared to control during the acquisition test. It increased "time spent" (%) in the target quadrant. Reelin level was enhanced in rats treated with beta boswellic acid. Tau hyperphosphorylation (p-tau404) and glial fibrillary acidic protein were decreased in the prevention group while the expression of reelin protein in both groups was increased. We could suggest that the anti-inflammatory property of beta boswellic acid is one of the main factors involving in the improvement of learning and memory in rats. Therefore the antineurodegenerative effect of beta boswellic acid may be due to its ability to reactivate reelin protein.

Toxic Substance-induced Hippocampal Neurodegeneration in Rodents as Model of Alzheimer’s Dementia

BACKGROUND: Alzheimer’s Dementia (AD) cases are increasing with the global elderly population. To study the part of the brain affected by AD, animal models for hippocampal degeneration are still necessary to better understand AD pathogenesis and develop treatment and prevention measures. AIM: This study was a systematic review of toxic substance-induced animal models of AD using the Morris Water Maze method in determining hippocampal-related memory impairment. Our aim was reviewing the methods of AD induction using toxic substances in laboratory rodents and evaluating the report of the AD biomarkers reported in the models. METHODS: Data were obtained from articles in the PubMed database, then compiled, categorized, and analyzed. Eighty studies published in the past 5 years were included for analysis. RESULTS AND DISCUSSION: The most widely used method was intracerebroventricular injection of amyloid-β _substances. However, some less technically challenging techniques using oral or intraperitoneal administration of other toxic substances also produce successful models. Instead of hippocampal neurodegeneration, many studies detected biomarkers of the AD pathological process while some reported inflammation, oxidative stress, neurotrophic factors, and changes of cholinergic activity. Female animals were underrepresented despite a high incidence of AD in women. CONCLUSION: Toxic substances may be used to develop AD animal models characterized with appropriate AD pathological markers. Characterization of methods with the most easy-handling techniques and more studies in female animal models should be encouraged.

Sinapic Acid Alleviates Oxidative Stress and Neuro-Inflammatory Changes in Sporadic Model of Alzheimer's Disease in Rats

The role of oxidative stress, neuro-inflammation and cholinergic dysfunction is already established in the development of Alzheimer's disease (AD). Sinapic acid (SA), a hydroxylcinnamic acid derivative, has shown neuro-protective effects. The current study evaluates the neuro-protective potential of SA in intracerebroventricular streptozotocin (ICV-STZ) induced cognitive impairment in rats. Male Wistar rats were bilaterally injected with ICV-STZ. SA was administered intragastrically once daily for three weeks. Rats were divided into sham, ICV-STZ, STZ + SA (10 mg/kg), STZ + SA (20 mg/kg) and SA per se (20 mg/kg). Behavioral tests were assessed on day 0 and 21 days after STZ. Later, rats were sacrificed for biochemical parameters, pro-inflammatory cytokines, choline acetyltransferase (ChAT) expression and neuronal loss in the CA1 region of the hippocampus. The results showed that SA 20 mg/kg significantly (p < 0.05) improved cognitive impairment as assessed by Morris water maze and passive avoidance tests. SA 20 mg/kg reinstated the altered levels of GSH, MDA, TNF-α and IL-1β in the cortex and hippocampus. STZ-induced decreased expression of ChAT and neuronal loss were also significantly (p < 0.05) improved with SA. Our results showed that SA exhibits neuro-protection against ICV-STZ induced oxidative stress, neuro-inflammation, cholinergic dysfunction and neuronal loss, suggesting its potential in improving learning and memory in patients of AD.

Intracerebral Injection of Streptozotocin to Model Alzheimer Disease in Rats

Animal models have promoted meaningful contribution to science including Alzheimer's disease (AD) research. Several animal models for AD have been used, most of them related to genetic mutations observed in familial AD. However, sporadic form of AD, also named late-onset is the most frequent form of the disease, which is multifactorial, being influenced by genetic, environmental and lifestyle factors. Here, we describe a protocol of an AD-like pathology of the sporadic form using Wistar rats by a single bilateral intracerebroventricular (icv) injection of streptozotocin (STZ, 2 mg/kg). Icv injection of STZ induces brain resistance to insulin and other pathological alterations related to those observed in AD, such as cognitive impairment and accumulation of phosphorylated tau protein and β-amyloid in the brain. Thus, icv injection of STZ is a useful tool to investigate the pathological mechanisms and the metabolic alterations involved in AD and to propose new therapeutic approaches and neuroprotective drugs.

Moderate protective effect of Kyotorphin against the late consequences of intracerebroventricular streptozotocin model of Alzheimer's disease

The established decrease in the level of endogenous kyotorphin (KTP) into the cerebrospinal fluid of patients with an advanced stage of Alzheimer's disease (AD) and the found neuroprotective activity of KTP suggested its participation in the pathophysiology of the disease. We aimed to study the effects of subchronic intracerebroventricular (ICV) treatment (14 days) with KTP on the behavioral, biochemical and histological changes in rats with streptozotocin (STZ-ICV)-induced model of sporadic AD (sAD). Three months after the administration of STZ-ICV, rats developed increased locomotor activity, decreased level of anxiety, impaired spatial and working memory. Histological data from the STZ-ICV group demonstrated decreased number of neurons in the CA1 and CA3 subfields of the hippocampus. The STZ-ICV group was characterized with a decrease of total protein content in the hippocampus and the prefrontal cortex as well as increased levels of the carbonylated proteins in the hippocampus. KTP treatment of STZ-ICV rats normalized anxiety level and regained object recognition memory. KTP abolished the protein loss in prefrontal cortex and decrease the neuronal loss in the CA3 subfield of the hippocampus. STZ-ICV rats, treated with KTP, did not show significant changes in the levels of the carbonylated proteins in specific brain structures or in motor activity and spatial memory compared to the saline-treated STZ-ICV group. Our data show a moderate and selective protective effect of a subchronic ICV administration of the dipeptide KTP on the pathological changes induced by an experimental model of sAD in rats.

Psychological stress effects on myelin degradation in the cuprizone-induced model of demyelination

Multiple sclerosis (MS) is known as the most common demyelinating disease worldwide in which previous studies have shown that stress is a risk factor for the disease's onset and progression. Nevertheless, further studies are needed to investigate the consequences of stress in MS pathology. In this study, after 5 days of exposure to psychological and physical stress as a repetitive distress modality, rats were treated with cuprizone. The demyelination degree was compared in animal groups using Luxol fast blue staining, immunohistochemical staining for myelin basic protein and transmission electron microscopy. Outcomes revealed that animals exposed to stress prior to cuprizone ingestion, elicit more intense demyelination. Continuous psychological distress has more severe effects on myelin sheath destruction in the preclinical stage.