Association of lipocalin-type prostaglandin D synthase with disproportionately enlarged subarachnoid-space in idiopathic normal pressure hydrocephalus

Differential effect of an evolving amyloid and tau pathology on brain phospholipids and bioactive lipid mediators in rat models of Alzheimer-like pathology

BACKGROUND

Brain inflammation contributes significantly to the pathophysiology of Alzheimer's disease, and it is manifested by glial cell activation, increased production of cytokines/chemokines, and a shift in lipid mediators from a pro-homeostatic to a pro-inflammatory profile. However, whether the production of bioactive lipid mediators is affected at earlier stages, prior to the deposition of Aβ plaques and tau hyperphosphorylation, is unknown. The differential contribution of an evolving amyloid and tau pathology on the composition and abundance of membrane phospholipids and bioactive lipid mediators also remains unresolved.

METHODS

In this study, we examined the cortical levels of DHA- and AA-derived bioactive lipid mediators and of membrane phospholipids by liquid chromatography with tandem mass spectrometry in transgenic rat models of the Alzheimer's-like amyloid and tau pathologies at early and advanced pathological stages.

RESULTS

Our findings revealed a complex balance between pro-inflammatory and pro-resolving processes in which tau pathology has a more pronounced effect compared to amyloid pathology. At stages preceding tau misfolding and aggregation, there was an increase in pro-resolving lipid mediators (RVD6 and NPD1), DHA-containing phospholipids and IFN-γ levels. However, in advanced tau pathology displaying NFT-like inclusions, neuronal death, glial activation and cognitive deficits, there was an increase in cytokine and PGD2, PGE2, and PGF2α generation accompanied by a drop in IFN-γ levels. This pathology also resulted in a marked increase in AA-containing phospholipids. In comparison, pre-plaque amyloid pathology already presented high levels of cytokines and AA-containing phospholipids together with elevated RVD6 and NPD1 levels. Finally, Aβ plaque deposition was accompanied by a modest increase in prostaglandins, increased AA-containing phospholipids and reduced DHA-containing phospholipids.

CONCLUSIONS

Our findings suggest a dynamic trajectory of inflammatory and lipid mediators in the evolving amyloid and tau pathologies and support their differing roles on membrane properties and, consequentially, on signal transduction.

Efficacy and safety of shunt surgery in patients with idiopathic normal-pressure hydrocephalus: can we predict shunt response by preoperative magnetic resonance imaging (MRI)?

AIM

The aim of this study was to identify preoperative magnetic resonance imaging (MRI) findings that can predict the shunt responsiveness in idiopathic normal-pressure hydrocephalus (iNPH) patients and to investigate postoperative outcome and complications.

MATERIALS AND METHODS

A total of 192 patients with iNPH who underwent shunt at our hospital between 2000 and 2021 were included to investigate complications. Of these, after exclusion, 127 (1-month postoperative follow-up) and 77 (1-year postoperative follow-up) patients were evaluated. The preoperative MRI features (the presence of tightness of the high-convexity subarachnoid space, Sylvian fissure enlargement, Evans' index, and callosal angle) of the shunt-response and nonresponse groups were compared, and a systematic review was conducted to evaluate whether preoperative MRI findings could predict shunt response.

RESULTS

Postoperative complications within one month after surgery were observed in 6.8% (13/192), and the most common complication was hemorrhage. Changes in corpus callosum were observed in 4.2% (8/192). The shunt-response rates were 83.5% (106/127) in the 1-month follow-up group and 70.1% (54/77) in 1-year follow-up group. In the logistic regression analysis, only Evans' index measuring >0.4 had a significant negative relationship with shunt response at 1-month follow-up; however, no significant relationship was observed at 1-year follow-up. According to our systematic review, it is still controversial whether preoperative MRI findings could predict shunt response.

CONCLUSION

Evans' index measure of >0.4 had a significant relationship with the shunt response in the 1-month follow-up group. In systematic reviews, there is ongoing debate about whether preoperative MRI findings can accurately predict responses to shunt surgery. Postoperative corpus callosal change was observed in 4.2% of iNPH patients.

Lipocalin-type prostaglandin D synthase: a glymphopathy marker in idiopathic hydrocephalus

Idiopathic normal pressure hydrocephalus in elderly people is considered a form of glymphopathy caused by malfunction of the waste clearance pathway, called the glymphatic system. Tau is a representative waste material similar to amyloid-β. During neurodegeneration, lipocalin-type prostaglandin D synthase (L-PGDS), a major cerebrospinal fluid (CSF) protein, is reported to act as a chaperone that prevents the neurotoxic aggregation of amyloid-β. L-PGDS is also a CSF biomarker in idiopathic normal pressure hydrocephalus and significantly correlates with tau concentration, age, and age-related brain white matter changes detected by magnetic resonance imaging. To investigate this glymphopathy, we aimed to analyze white matter changes and contributing factors in vivo and their interactions ex vivo. Cerebrospinal tap tests were performed in 60 patients referred for symptomatic ventriculomegaly. Patients were evaluated using an idiopathic normal pressure hydrocephalus grading scale, mini-mental state examination, frontal assessment battery, and timed up-and-go test. The typical morphological features of high convexity tightness and ventriculomegaly were measured using the callosal angle and Evans index, and parenchymal white matter properties were evaluated with diffusion tensor imaging followed by tract-based spatial statistics. Levels of CSF biomarkers, including tau, amyloid-β, and L-PGDS, were determined by ELISA, and their interaction, and localization were determined using immunoprecipitation and immunohistochemical analyses. Tract-based spatial statistics for fractional anisotropy revealed clusters that positively correlated with mini-mental state examination, frontal assessment battery, and callosal angle, and clusters that negatively correlated with age, disease duration, idiopathic normal pressure hydrocephalus grading scale, Evans index, and L-PGDS. Other parameters also indicated clusters that correlated with symptoms, microstructural white matter changes, and L-PGDS. Tau co-precipitated with L-PGDS, and colocalization was confirmed in postmortem specimens of neurodegenerative disease obtained from the human Brain Bank. Our study supports the diagnostic value of L-PGDS as a surrogate marker for white matter integrity in idiopathic normal pressure hydrocephalus. These results increase our understanding of the molecular players in the glymphatic system. Moreover, this study indicates the potential utility of enhancing endogenous protective factors to maintain brain homeostasis.

Normal-Tension Glaucoma and Potential Clinical Links to Alzheimer's Disease

Glaucoma is a group of optic neuropathies and the world's leading cause of irreversible blindness. Normal-tension glaucoma (NTG) is a subtype of glaucoma that is characterized by a typical pattern of peripheral retinal loss, in which the patient's intraocular pressure (IOP) is considered within the normal range (<21 mmHg). Currently, the only targetable risk factor for glaucoma is lowering IOP, and patients with NTG continue to experience visual field loss after IOP-lowering treatments. This demonstrates the need for a better understanding of the pathogenesis of NTG and underlying mechanisms leading to neurodegeneration. Recent studies have found significant connections between NTG and cerebral manifestations, suggesting NTG as a neurodegenerative disease beyond the eye. Gaining a better understanding of NTG can potentially provide new Alzheimer's Disease diagnostics capabilities. This review identifies the epidemiology, current biomarkers, altered fluid dynamics, and cerebral and ocular manifestations to examine connections and discrepancies between the mechanisms of NTG and Alzheimer's Disease.

Biochemical and Structural Characteristics, Gene Regulation, Physiological, Pathological and Clinical Features of Lipocalin-Type Prostaglandin D2 Synthase as a Multifunctional Lipocalin

Lipocalin-type prostaglandin (PG) D₂ synthase (L-PGDS) catalyzes the isomerization of PGH₂, a common precursor of the two series of PGs, to produce PGD₂. PGD₂ stimulates three distinct types of G protein-coupled receptors: (1) D type of prostanoid (DP) receptors involved in the regulation of sleep, pain, food intake, and others; (2) chemoattractant receptor-homologous molecule expressed on T helper type 2 cells (CRTH2) receptors, in myelination of peripheral nervous system, adipocyte differentiation, inhibition of hair follicle neogenesis, and others; and (3) F type of prostanoid (FP) receptors, in dexamethasone-induced cardioprotection. L-PGDS is the same protein as β-trace, a major protein in human cerebrospinal fluid (CSF). L-PGDS exists in the central nervous system and male genital organs of various mammals, and human heart; and is secreted into the CSF, seminal plasma, and plasma, respectively. L-PGDS binds retinoic acids and retinal with high affinities (Kd < 100 nM) and diverse small lipophilic substances, such as thyroids, gangliosides, bilirubin and biliverdin, heme, NAD(P)H, and PGD₂, acting as an extracellular carrier of these substances. L-PGDS also binds amyloid β peptides, prevents their fibril formation, and disaggregates amyloid β fibrils, acting as a major amyloid β chaperone in human CSF. Here, I summarize the recent progress of the research on PGD₂ and L-PGDS, in terms of its “molecular properties,” “cell culture studies,” “animal experiments,” and “clinical studies,” all of which should help to understand the pathophysiological role of L-PGDS and inspire the future research of this multifunctional lipocalin.

The association of disproportionately enlarged subarachnoid space hydrocephalus with cognitive deficit in a general population: the Ohasama study

Disproportionately enlarged subarachnoid space hydrocephalus (DESH) is the characteristic feature of idiopathic normal pressure hydrocephalus. We aimed to characterize the prevalence, development, and association of DESH to cognitive deficit in a large population. We reviewed the data of 1384 subjects eligible for the present study among 1590 participants who underwent magnetic resonance imaging (MRI) in the Ohasama Study, a population-based study in Ohasama, Japan. The participants with Mini-Mental State Examination (MMSE) score <  = 25 were assumed to have cognitive deficit and DESH was evaluated by reviewing the MRIs. We assessed the association between DESH, Evans index (EI), and cognitive deficit using multivariate logistic regression models adjusted for relevant confounders. Furthermore, we evaluated the new development of DESH and the deterioration of cognitive function in the participants with DESH. There were nine participants with DESH (0.65%), seven of whom showed cognitive deficit. DESH was significantly associated with cognitive deficit in multivariate regression analyses (odds ratio; 8.50 [95% confidence interval: 1.61–44.88]). In the 669 participants who underwent follow-up MRI, we found four participants newly presenting with DESH; the development of DESH was observed before/after the presence of EI > 0.3. We also found two participants with existing DESH showing no remarkable worsening in MMSE and EI. The present study demonstrated a positive association between the presence of DESH and cognitive deficit. DESH can develop independently of EI > 0.3, and ventricular enlargement in combination with DESH may be an important factor in the worsening of cognitive deficit.

Prognostic Utility of Disproportionately Enlarged Subarachnoid Space Hydrocephalus in Idiopathic Normal Pressure Hydrocephalus Treated with Ventriculoperitoneal Shunt Surgery: A Systematic Review and Meta-analysis

BACKGROUND

Disproportionately enlarged subarachnoid space hydrocephalus is a specific radiologic marker for idiopathic normal pressure hydrocephalus. However, controversy exists regarding the prognostic utility of disproportionately enlarged subarachnoid space hydrocephalus.

PURPOSE

Our aim was to evaluate the prevalence of disproportionately enlarged subarachnoid space hydrocephalus in idiopathic normal pressure hydrocephalus and its predictive utility regarding prognosis in patients treated with ventriculoperitoneal shunt surgery.

DATA SOURCES

We used MEDLINE and EMBASE databases.

STUDY SELECTION

We searched for studies that reported the prevalence or the diagnostic performance of disproportionately enlarged subarachnoid space hydrocephalus in predicting treatment response.

DATA ANALYSIS

The pooled prevalence of disproportionately enlarged subarachnoid space hydrocephalus was obtained. Pooled sensitivity, specificity, and area under the curve of disproportionately enlarged subarachnoid space hydrocephalus to predict treatment response were obtained. Subgroup and sensitivity analyses were performed to explain heterogeneity among the studies.

DATA SYNTHESIS

Ten articles with 812 patients were included. The pooled prevalence of disproportionately enlarged subarachnoid space hydrocephalus in idiopathic normal pressure hydrocephalus was 44% (95% CI, 34%-54%). The pooled prevalence of disproportionately enlarged subarachnoid space hydrocephalus was higher in the studies using the second edition of the Japanese Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus compared with the studies using the international guidelines without statistical significance (52% versus 43%, P = .38). The pooled sensitivity and specificity of disproportionately enlarged subarachnoid space hydrocephalus for prediction of treatment response were 59% (95% CI, 38%-77%) and 66% (95% CI, 57%-74%), respectively, with an area under the curve of 0.67 (95% CI, 0.63-0.71).

LIMITATIONS

The lack of an established method for assessing disproportionately enlarged subarachnoid space hydrocephalus using brain MR imaging served as an important cause of the heterogeneity.

CONCLUSIONS

Our meta-analysis demonstrated a relatively low prevalence of disproportionately enlarged subarachnoid space hydrocephalus in idiopathic normal pressure hydrocephalus and a poor diagnostic performance for treatment response.

Cyclooxygenase-2 Induced the β-Amyloid Protein Deposition and Neuronal Apoptosis Via Upregulating the Synthesis of Prostaglandin E2 and 15-Deoxy-Δ12,14-prostaglandin J2

Elevated levels of cyclooxygenase-2 (COX-2) and prostaglandins (PGs) have been shown to be involved in the pathogenesis of Alzheimer's disease. Analysis of the underlying mechanisms elucidated a function of sequential PGE2 and PGD2 synthesis in regulating β-amyloid protein (Aβ) deposition by modulating tumor necrosis factor α (TNF-α)-dependent presenilin (PS)1/2 activity in COX-2 and APP/PS1 crossed mice. Specifically, COX-2 overexpression accelerates the expression of microsomal PGE synthase-1 (mPGES-1) and lipocalin-type prostaglandin D synthase (L-PGDS), leading to the synthesis of PGE2 and 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) in 6-month-old APP/PS1 mice. Consequently, PGE2 has the ability to increase Aβ production by enhancing the expression of PS1/2 in a TNF-α-dependent manner, which accelerates the cognitive decline of COX-2/APP/PS1 mice. More interestingly, low concentrations of 15d-PGJ2 treatment facilitate the effects of PGE2 on the deposition of Aβ via TNF-α-dependent PS1/2 mechanisms. In contrast, high concentrations of 15d-PGJ2 treatment inhibit the deposition of Aβ via suppressing the expression of TNF-α-dependent PS1/2. In this regard, a high concentration of 15d-PGJ2 appears to be a therapeutic agent against Alzheimer's disease. However, the high 15d-PGJ2 concentration treatment induces neuronal apoptosis via increasing the protein levels of Bax, cleaved caspase-3, and DFF45, which further impairs the learning ability of APP/PS1 mice.

Integrated communications between cyclooxygenase-2 and Alzheimer's disease

Elevated levels of cyclooxygenase-2 (COX-2) and prostaglandins (PGs) are involved in the pathogenesis of Alzheimer's disease (AD), which is characterized by the accumulation of β-amyloid protein (Aβ) and tau hyperphosphorylation. However, the gaps in our knowledge of the roles of COX-2 and PGs in AD have not been filled. Here, we summarized the literature showing that COX-2 dysregulation obviously influences abnormal cleavage of β-amyloid precursor protein, aggregation and deposition of Aβ in β-amyloid plaques and the inclusion of phosphorylated tau in neurofibrillary tangles. Neuroinflammation, oxidative stress, synaptic plasticity, neurotoxicity, autophagy, and apoptosis have been assessed to elucidate the mechanisms of COX-2 regulation of AD. Notably, an imbalance of these factors ultimately produces cognitive decline. The current review substantiates our understanding of the mechanisms of COX-2-induced AD and establishes foundations for the design of feasible therapeutic strategies to treat AD.-Guan, P.-P., Wang, P. Integrated communications between cyclooxygenase-2 and Alzheimer's disease.

[Hakim-Adams syndrome]

Hakim-Adams syndrome is little known, although quite common disease. The etiology is not fully clear. Pathogenetic mechanisms included the blockage of cerebrospinal fluid outflow along the upper lateral surface of the brain, development of hydrocephalus with the expansion of the brain ventricles while maintaining normotensive cerebrospinal fluid (CSF). Main manifestations are ataxia, apraxia, symptoms of dementia and urinary disturbances, up to incontinence. Diagnosis is based on clinical symptoms, exploratory lumbar and neuroimaging. Main treatment is ventriculoperitoneal (stomach) shunt placement for fluid drainage. Timely surgical intervention gives good results and improves quality of life of patients.

Cerebrospinal fluid biomarkers for prognosis of long-term cognitive treatment outcomes in patients with idiopathic normal pressure hydrocephalus

The prognosis of cognitive improvement after cerebrospinal fluid (CSF) shunting in idiopathic normal pressure hydrocephalus (iNPH) remains uncertain, with no reports on CSF biomarkers related to long-term cognitive prognosis. We performed a preliminary study of CSF biomarker protein levels for cognitive outcome prognostication of two-year outcomes after shunt treated iNPH in 36 patients (13 women) with a median age of 75years (IQR 69-78). CSF biomarkers included soluble amyloid precursor proteins (sAPP, sAPPα, sAPPβ), amyloid β (Aβ)1-38, Aβ1-42 and phosphorylated tau (p-tau), lipocalin-type prostaglandin D synthase (L-PGDS)/β-trace, and cystatin C. The results clearly showed that p-tau levels (sensitivity of 71.4%, specificity of 77.8%, cut-off value of 22.0pg/mL), Aβ1-38/Aβ1-42 ratio (77.8%, 81%, 3.58), and the Aβ1-42/p-tau ratio (76%, 72.7%, 14.6) in preoperative CSF have the potential to determine postoperative prognosis. Improved cognition may be associated with the improvement in CSF circulation after LPS, which likely induces cystatin C and L-PGDS and switches synthesis from Aβ1-42 to Aβ1-38.

Disproportionate subarachnoid space hydrocephalus-outcome and perivascular space

Objective

We sought to identify the prevalence of MRI features of disproportionately enlarged subarachnoid space hydrocephalus in possible idiopathic normal pressure hydrocephalus (DESH-iNPH) and to describe the clinico-radiological features and outcomes of a community-based investigation (The Vienna Trans-Danube Aging study).

Methods

Of the 697 inhabitants (all 75 years old), 503 completed extensive neurological examinations at baseline and were followed up every 30 months thereafter with MRIs, mini-mental state examination (MMSE), and the Unified Parkinson Disease Rating Scale-Motor Section (UPDRSM). The DESH-iNPH participant data were compared with the data from participants with Evans index ratios >0.3 (ex vacuo hydrocephalus), cerebral small-vessel diseases, and normal MRIs. The widening of perivascular space was also evaluated by MRI in these groups.

Results

Eight participants with DESH-iNPH (1.6%) and 76 with ex vacuo hydrocephalus (16.1%) at baseline were identified. The mean MMSE in DESH-iNPH, ex vacuo hydrocephalus, and normal MRIs was 26.4, 27.9, and 28.3, respectively, and the mean UPDRSM was 9.75, 2.96, and 1.87, respectively. After a 90-month follow-up, the mortality rates for DESH-iNPH, ex vacuo hydrocephalus, and normal MRIs were 25.0%, 21.3%, and 10.9%, respectively. The perivascular-space widening scores were significantly smaller in the DESH-iNPH cases, particularly at the centrum semiovale, compared to cerebral small-vessel disease and ex vacuo hydrocephalus cases.

Interpretation

The prevalence of DESH-iNPH was 1.6% for participants aged 75 years and revealed significantly lower MMSE and higher UPDRSM scores compared to the ex vacuo hydrocephalus and controls. Moreover, it is suggested that perivascular-space narrowing is a morphological and pathophysiological marker of DESH-iNPH.

News from the editors of Fluids and Barriers of the CNS

This editorial announces a new affiliation between Fluids and Barriers of the CNS (FBCNS) and the International Brain Barriers Society (IBBS) with mutual benefits to the journal and to society members. This is a natural progression from the appointment of two new Co-Editors in Chief: Professor Lester Drewes and Professor Richard Keep in 2013. FBCNS provides a unique and specialist platform for the publication of research in the expanding fields of brain barriers and brain fluid systems in both health and disease.