Assessment of lipophilic fluorescence products in β-amyloid-induced cognitive decline: A parallel track in hippocampus, CSF, plasma and erythrocytes

The preventive effects of Saccharomyces boulardii against oxidative stress induced by lipopolysaccharide in rat brain

The brain is sensitive to oxidative stress, which can trigger microglial activation and neuroinflammation. Antioxidant therapies may provide neuroprotection against oxidative stress. In recent years antioxidant effects of probiotics and their possible mechanisms in oxidative stress-related models have been determined. In the current study, for the first time, we assessed the effects of Saccharomyces boulardii on oxidative stress provoked by lipopolysaccharide (LPS) in the rat brain. Four groups of animals were used, including the control, LPS, S. boulardii + LPS, and S. boulardii groups. All animals received either saline or S. boulardii (1010 CFU) by gavage for four weeks. Between days 14 and 22, all animals received either LPS (250 μg/kg) or saline by intraperitoneal (i.p.) injection. S. boulardii was able to inhibit lipid peroxidation and prevent the reduction of antioxidant levels, including glutathione and catalase in the model of oxidative stress induced by LPS in the rat hippocampus and cortex. Also, it increased the lowered ratio of glutathione/oxidized glutathione in both tissues. Serum levels of anti-inflammatory interleukin 10 (IL-10) and proinflammatory cytokines IL-6 and IL-8 increased and decreased, respectively. S. boulardii has potential antioxidant activities in oxidative stress-related model, possibly modulating gut microbiota, immune defense, and antioxidant enzyme activities that can be considered in preventing oxidative stress-related central nervous system (CNS) diseases.

The increment of annexin V-positive microvesicles versus annexin V-negative microvesicles in CSF of an animal model of Alzheimer's disease

OBJECTIVE

Extracellular microvesicles (MVs) as a specific signaling molecule have received much attention in nervous system studies. Alterations in the tissue redox status in pathological conditions, such as Alzheimer's disease (AD), facilitate the translocation of cell membrane phosphatidylserine to the outer leaflet and lead to the MVs shedding. Annexin V binds with high affinity to phosphatidylserine. Some arguments exist about whether Annexin V-negative MVs should be considered in pathological conditions.

MATERIAL AND METHOD

We compared the kinetics of two phenotypes of Annexin V-positive and Annexin V-negative MVs in the cerebrospinal fluid (CSF) of amyloid-β (Aβ)-treated male Wistar rats with flow cytometry technique. The Aβ was injected bilaterally into the cerebral ventricles. Thioflavin T staining was used to confirm the presence of hippocampal Aβ fibrils two weeks post-Aβ injection. Levels of hippocampal interleukin-1β were assessed as an inflammatory index. The CSF malondialdehyde (MDA) concentration was determined. The cognitive impairment and anxiety behaviors were assessed by object recognition and elevated plus maze tests, respectively.

RESULTS

Elevation of MDA levels and a significant rise in the scoring of IL-1β staining were found in the Aβ group. The Aβ induced anxiogenic behavior, impaired novel object recognition memory, and increased the CSF levels of the total number of MVs. The number of Annexin V-positive MVs was significantly higher than Annexin V-negative MVs in all groups.

CONCLUSION

Data showed that Annexin V-positive MVs potentially have a significant contribution to the pathophysiology of the Aβ-induced cognitive impairment. To catch a clear image of microvesicle production in pathological conditions, both phenotypes of Annexin V-positive and Annexin V-negative MVs should be analyzed and reported.

Advances in Amyloid-β Clearance in the Brain and Periphery: Implications for Neurodegenerative Diseases

This review examines the role of impaired amyloid-β clearance in the accumulation of amyloid-β in the brain and the periphery, which is closely associated with Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA). The molecular mechanism underlying amyloid-β accumulation is largely unknown, but recent evidence suggests that impaired amyloid-β clearance plays a critical role in its accumulation. The review provides an overview of recent research and proposes strategies for efficient amyloid-β clearance in both the brain and periphery. The clearance of amyloid-β can occur through enzymatic or non-enzymatic pathways in the brain, including neuronal and glial cells, blood-brain barrier, interstitial fluid bulk flow, perivascular drainage, and cerebrospinal fluid absorption-mediated pathways. In the periphery, various mechanisms, including peripheral organs, immunomodulation/immune cells, enzymes, amyloid-β-binding proteins, and amyloid-β-binding cells, are involved in amyloid-β clearance. Although recent findings have shed light on amyloid-β clearance in both regions, opportunities remain in areas where limited data is available. Therefore, future strategies that enhance amyloid-β clearance in the brain and/or periphery, either through central or peripheral clearance approaches or in combination, are highly encouraged. These strategies will provide new insight into the disease pathogenesis at the molecular level and explore new targets for inhibiting amyloid-β deposition, which is central to the pathogenesis of sporadic AD (amyloid-β in parenchyma) and CAA (amyloid-β in blood vessels).

A surgical modification in the technique of rat pinealectomy

BACKGROUND

Several experimental intents require pineal gland removal. The main challenge of the pinealectomy surgical procedure is the hemorrhage due to the transverse sinus torn. The study aimed to modify the rat pinealectomy surgical procedure to reduce the risk of bleeding and the mortality rate.

METHODS

Adult male rats experienced pinealectomy surgery. A mini-drill was used to remove a small skull area in the junction of the lambda and sagittal sutures. The pineal gland was removed using a curved-head hook. Animals experienced intensive post-surgical care. Locomotion, cerebellar motor function, working memory, and anxiety were evaluated 2 weeks after pinealectomy by the open field, rotarod, Y maze, and the elevated plus maze, respectively.

RESULTS

Surgical modification reduced the bleeding risk and animal mortality rate. No significant alteration was found in locomotion and working memory. However, the pinealectomy was anxiogenic and decreased entry to the open arm. The cerebellar motor performance did not change in the rotarod test. Hematoxylin-Eosin staining of removed tissue confirmed the histology of the pineal gland.

CONCLUSION

Advantages of this technique were removing a small skull area, modifying the hook insertion point to prevent damaging the brain veins, reducing the bleeding risk and the mortality rate. Surgery modification was associated with a decreased final number of animals used. Regardless of the melatonin shortage, pinealectomy affects different organs, which should be considered in the research study design.

Increment of CSF fractalkine-positive microvesicles preceded the spatial memory impairment in amyloid beta neurotoxicity

BACKGROUND

Fractalkine (CX₃CL₁) is a key chemokine, affects neuronal cell communication and involves in Alzheimer's disease pathogenesis. Microvesicles (MVs) participate in neuronal cells' cross-talk in physiological and pathological states. Microvesicles released in cerebrospinal fluid (CSF) may provide a valuable footprint of brain changes. Little information is available regarding the release of fractalkine-positive MVs (CX₃CL₁⁺ -MVs) in the nervous system.

METHODS

We induced cognitive impairment by bilateral injection of amyloid-beta (Aβ) into the cerebral ventricles. We analyzed the CSF by flow cytometry in two experiments (trained and untrained) to elucidate the presence of CX₃CL₁⁺ -MVs. The hippocampal TNF-α as an inflammatory factor was assessed by immunohistochemistry.

RESULTS

The Aβ induced spatial memory impairment after two weeks, verified by a decrease in the escape latency in Morris water maze test. It caused an increase in the anxiety-like behaviors demonstrated by a decrease in entries into the open arms of elevated plus maze test. The Aβ increased the percent of the positive area for TNF-α staining. Histological evaluation of the hippocampus confirmed the tissue injuries. The CSF levels of CX₃CL₁⁺ -MVs, increased 2 and 7 days after Aβ injection. The Aβ increased the TNF-α staining and provided an inflammatory context to facilitate the MVs release. The rise of CX₃CL₁⁺ -MVs was transient and subsided after two weeks. Both trained and untrained experiments showed a similar rise pattern of CX₃CL₁⁺ -MVs.

CONCLUSION

Increase of fractalkine-positive microvesicles preceded the cognitive impairment, more studies are required to approve the CX₃CL₁⁺ -MVs as a potential biomarker in the early diagnosis of Alzheimer's disease.