Beta adrenoceptor blockade ameliorates impaired glucose tolerance and alterations of the cerebral ceramide metabolism in an experimental model of ischemic stroke

Translatome analysis in acute ischemic stroke: Astrocytes and microglia exhibit differences in poststroke alternative splicing of expressed transcripts

Astrocytes and microglia undergo dynamic and complex morphological and functional changes following ischemic stroke, which are instrumental in both inflammatory responses and neural repair. While gene expression alterations poststroke have been extensively studied, investigations into posttranscriptional regulatory mechanisms, specifically alternative splicing (AS), remain limited. Utilizing previously reported Ribo-Tag-seq data, this study analyzed AS alterations in poststroke astrocytes and microglia from young adult male and female mice. Our findings reveal that in astrocytes, compared to the sham group, 109 differential alternative splicing (DAS) events were observed at 4 h poststroke, which increased to 320 at day 3. In microglia, these numbers were 316 and 266, respectively. Interestingly, the disparity between DAS genes and differentially expressed genes is substantial, with fewer than 10 genes shared at both poststroke time points in astrocytes and microglia. Gene ontology enrichment analysis revealed the involvement of these DAS genes in diverse functions, encompassing immune response (Adam8, Ccr1), metabolism (Acsl6, Pcyt2, Myo5a), and developmental cell growth (App), among others. Selective DAS events were further validated by semiquantitative RT-PCR. Overall, this study comprehensively describes the AS alterations in astrocytes and microglia during the hyperacute and acute phases of ischemic stroke and underscores the significance of certain hub DAS events in neuroinflammatory processes.

Acetyl Tributyl Citrate Exposure at Seemingly Safe Concentrations Induces Adverse Effects in Different Genders of Type 2 Diabetes Mice, Especially Brain Tissue

Acetyl tributyl citrate (ATBC) is a widely used phthalate substitute. Although ATBC is considered to be with a safe dosage of up to 1000 mg/kg/day, studies on its effects in some sensitive populations, such as diabetic patients, are relatively rare. Epidemiological studies have shown that there is a link between diabetes and nervous system diseases. However, toxicological studies have not fully confirmed this yet. In this study, glycolipid metabolism, cognitive deficits, brain tissue damage, levels of neurotransmitters, beta-amyloid plaques (Aβ), hyperphosphorylated tau protein (p-Tau), oxidative stress and inflammation, as well as glial cell homeostatic levels in the brain tissue of type 2 diabetes (T2DM) mice, were determined after ATBC exposure (0, 2, 20, and 200 mg/kg/day) for 90 days. The results confirmed that ATBC exposure aggravated the disorder of glycolipid metabolism and caused cognitive deficits in T2DM mice; induced histopathological alterations and Aβ and p-Tau accumulation, and reduced the levels of 5-hydroxytryptamine and acetylcholine in T2DM mouse brains; oxidative stress and glial cell homeostatic levels in T2DM mouse brains were also changed. Some of the adverse effects were gender-dependent. These findings support the theory that T2DM mice, especially males, are more sensitive to ATBC exposure. Although the safe dose of ATBC is high, prolonged exposure at seemingly safe concentrations has the potential to aggravate diabetes symptoms and cause brain tissue damage in T2DM mice.

Ceramide in cerebrovascular diseases

Ceramide, a bioactive sphingolipid, serves as an important second messenger in cell signal transduction. Under stressful conditions, it can be generated from de novo synthesis, sphingomyelin hydrolysis, and/or the salvage pathway. The brain is rich in lipids, and abnormal lipid levels are associated with a variety of brain disorders. Cerebrovascular diseases, which are mainly caused by abnormal cerebral blood flow and secondary neurological injury, are the leading causes of death and disability worldwide. There is a growing body of evidence for a close connection between elevated ceramide levels and cerebrovascular diseases, especially stroke and cerebral small vessel disease (CSVD). The increased ceramide has broad effects on different types of brain cells, including endothelial cells, microglia, and neurons. Therefore, strategies that reduce ceramide synthesis, such as modifying sphingomyelinase activity or the rate-limiting enzyme of the de novo synthesis pathway, serine palmitoyltransferase, may represent novel and promising therapeutic approaches to prevent or treat cerebrovascular injury-related diseases.

Determination of endogenous sphingolipid content in stroke rats and HT22 cells subjected to oxygen-glucose deprivation by LC‒MS/MS

BACKGROUND

Stroke is the leading cause of death in humans worldwide, and its incidence increases every year. It is well documented that lipids are closely related to stroke. Analyzing the changes in lipid content in the stroke model after absolute quantification and investigating whether changes in lipid content can predict stroke severity provides a basis for the combination of clinical stroke and quantitative lipid indicators.

METHODS

This paper establishes a rapid, sensitive, and reliable LC‒MS/MS analytical method for the detection of endogenous sphingolipids in rat serum and brain tissue and HT22 cells and quantifies the changes in sphingolipid content in the serum and brain tissue of rats from the normal and pMCAO groups and in cells from the normal and OGD/R groups. Using sphingosine (d17:1) as the internal standard, a chloroform: methanol (9:1) mixed system was used for protein precipitation and lipid extraction, followed by analysis by reversed-phase liquid chromatography coupled to triple quadrupole mass spectrometry.

RESULTS

Based on absolute quantitative analysis of lipids in multiple biological samples, our results show that compared with those in the normal group, the contents of sphinganine (d16:0), sphinganine (d18:0), and phytosphingosine were significantly increased in the model group, except sphingosine-1-phosphate, which was decreased in various biological samples. The levels of each sphingolipid component in serum fluctuate with time.

CONCLUSION

This isotope-free and derivatization-free LC‒MS/MS method can achieve absolute quantification of sphingolipids in biological samples, which may also help identify lipid biomarkers of cerebral ischemia.

Brain to periphery in acute ischemic stroke: Mechanisms and clinical significance

The social and public health burdens of ischemic stroke have been increasing worldwide. In addition to focal brain damage, acute ischemic stroke (AIS) provokes systemic abnormalities across peripheral organs. AIS profoundly alters the autonomic nervous system, hypothalamic-pituitary-adrenal axis, and immune system, which further yield deleterious organ-specific consequences. Poststroke systemic pathological alterations in turn considerably contribute to the progression of ischemic brain injury, which accounts for the substantial impact of systemic complications on stroke outcomes. This review provides a comprehensive and updated pathophysiological model elucidating the systemic effects of AIS. To address their clinical significance and inform stroke management, we also outline the resulting systemic complications at particular stages of AIS and highlight the mechanisms. Future therapeutic strategies should attempt to integrate the treatment of primary brain lesions with interventions for secondary systemic complications, and should be tailored to patient individualized characteristics to optimize stroke outcomes.

Toll-Like Receptor Signaling Pathways: Novel Therapeutic Targets for Cerebrovascular Disorders

Toll-like receptors (TLRs), a class of pattern recognition proteins, play an integral role in the modulation of systemic inflammatory responses. Cerebrovascular diseases (CVDs) are a group of pathological conditions that temporarily or permanently affect the brain tissue mostly via the decrease of oxygen and glucose supply. TLRs have a critical role in the activation of inflammatory cascades following hypoxic-ischemic events and subsequently contribute to neuroprotective or detrimental effects of CVD-induced neuroinflammation. The TLR signaling pathway and downstream cascades trigger immune responses via the production and release of various inflammatory mediators. The present review describes the modulatory role of the TLR signaling pathway in the inflammatory responses developed following various CVDs and discusses the potential benefits of the modulation of different TLRs in the improvement of functional outcomes after brain ischemia.

Serum ceramide concentrations are associated with depression in patients after ischemic stroke-A two-center case-controlled study

BACKGROUND AND AIMS

The present study aims to correlate the severity of post-stroke depression (PSD) and serum ceramide concentration.

MATERIALS AND METHODS

In this two-center case-control study, we prospectively collected clinical and demographical information from age and gender-matched 51 PSD patients, 56 non-post-stroke depression (Non-PSD) patients, and 39 patients with major depression (MD) to perform the suitable biochemical analysis to bring a correlation in causing depression in patients soon after the stroke. The ROC curve method was used to evaluate ceramide's diagnostic efficacy in all three groups of patients. A follow-up analysis was also conducted based on PSD severity to associate serum ceramide levels and neuropsychiatric symptoms. The severity of the patient's depressive symptoms was assessed by using the self-rating depression scale (SDS).

RESULTS

In comparison between PSD and MD patients, three serum ceramide species were found to be significantly different. Compared with Non-PSD patients, PSD patients had significantly higher levels of all the four serum ceramides, and increasing levels ofC16:0, C18:0(VS MD) and C16: 0(VS Non-PSD) serve as a diagnostic tool and an independent risk factor in all three categories of patients. Moreover, the follow-up analysis results showed that, as the treatment progressed, the differences in the 3 serum ceramide species were statistically significant.

CONCLUSION

There was a stage-specific association between serum ceramides and PSD, and the potential pathophysiological mechanism has to be investigated in future research.

A Sphingosine 1-Phosphate Gradient Is Linked to the Cerebral Recruitment of T Helper and Regulatory T Helper Cells during Acute Ischemic Stroke

Emerging evidence suggests a complex relationship between sphingosine 1-phosphate (S1P) signaling and stroke. Here, we show the kinetics of S1P in the acute phase of ischemic stroke and highlight accompanying changes in immune cells and S1P receptors (S1P_R). Using a C57BL/6 mouse model of middle cerebral artery occlusion (MCAO), we assessed S1P concentrations in the brain, plasma, and spleen. We found a steep S1P gradient from the spleen towards the brain. Results obtained by qPCR suggested that cells expressing the S1P_R type 1 (S1P₁⁺) were the predominant population deserting the spleen. Here, we report the cerebral recruitment of T helper (T_H) and regulatory T (T_REG) cells to the ipsilateral hemisphere, which was associated with differential regulation of cerebral S1P_R expression patterns in the brain after MCAO. This study provides insight that the S1P-S1P_R axis facilitates splenic T cell egress and is linked to the cerebral recruitment of S1P_R⁺ T_H and T_REG cells. Further insights by which means the S1P-S1P_R-axis orchestrates neuronal positioning may offer new therapeutic perspectives after ischemic stroke.

Effects of β-Adrenergic Blockade on Metabolic and Inflammatory Responses in a Rat Model of Ischemic Stroke

Ischemic stroke provokes an inflammatory response concurrent with both sympathetic nervous system activation and hyperglycemia. Currently, their crosstalk and consequences in stroke outcomes are of clinical attraction. We have provided experimental evidence showing the suppressive effects of the nonselective β-adrenoreceptor antagonist propranolol on hyperglycemia, inflammation, and brain injury in a rat model experiencing cerebral ischemia. Pretreatment with propranolol protected against postischemic brain infarction, edema, and apoptosis. The neuroprotection caused by propranolol was accompanied by a reduction in fasting glucose, fasting insulin, glucose tolerance impairment, plasma C-reactive protein, plasma free fatty acids, plasma corticosterone, brain oxidative stress, and brain inflammation. Pretreatment with insulin alleviated-while glucose augmented-postischemic brain injury and inflammation. Additionally, the impairment of insulin signaling in the gastrocnemius muscles was noted in rats with cerebral ischemia, with propranolol improving the impairment by reducing oxidative stress and tumor necrosis factor-α signaling. The anti-inflammatory effects of propranolol were further demonstrated in isoproterenol-stimulated BV2 and RAW264.7 cells through its ability to decrease cytokine production. Despite their potential benefits, stroke-associated hyperglycemia and inflammation are commonly linked with harmful consequences. Our findings provide new insight into the anti-inflammatory, neuroprotective, and hypoglycemic mechanisms of propranolol in combating neurodegenerative diseases, such as stroke.