Multiple functions of the vesicular proton pump in nerve terminals

Proton Pump Inhibitors and Cognitive Health: Review on Unraveling the Dementia Connection and Co-morbid Risks

Dementia, an international health issue distinguished by the impairment of daily functioning due to cognitive decline, currently affects more than 55 million people worldwide, with the majority residing in low-income and middle-income countries. Globally, dementia entails significant economic burdens in 2019, amounting to a cost of 1.3 trillion US dollars. Informal caregivers devote considerable hours to providing care for those affected. Dementia imposes a greater caregiving and disability-adjusted life-year burden on women. A recent study has established a correlation between prolonged Proton Pump Inhibitor (PPI) usage and dementia, in addition to other neurodegenerative conditions. PPIs are frequently prescribed to treat peptic ulcers and GERD (gastroesophageal reflux disease) by decreasing stomach acid secretion. They alleviate acid-related symptoms through the inhibition of acid-secreting H+, K+ ATPase. In a number of observational studies, cognitive decline and dementia in the elderly have been linked to the use of PPIs. The precise mechanism underlying this relationship is unknown. These drugs might also alter the pH of brain cells, resulting in the accumulation of amyloid-beta (Aβ) peptides and the development of Alzheimer's disease (AD). Despite the compelling evidence supporting the association of PPIs with dementia, the results of studies remain inconsistent. The absence of a correlation between PPI use and cognitive decline in some studies emphasizes the need for additional research. Chronic PPI use can conceal underlying conditions, including cancer, celiac disease, vitamin B12 deficiency, and renal injury, highlighting dementia risk and the need for further investigations on cognitive health.

Association between Migraines and Prior Proton Pump Inhibitor Use: A Nested Case-Control Study Using a National Health Screening Cohort

The effect of proton pump inhibitor (PPI) use on migraine risk remains controversial. We explored the odds of migraines in relation to prior PPI use and treatment duration. Data from the Korean National Health Insurance Service-Health Screening Cohort (2002−2015) were analyzed in this nested case-control study involving 28,159 participants with incident migraines and 112,636 controls (1:4 matched by sex, age, income, and residential region). The baseline covariates were balanced by performing propensity score overlap weighting-based adjustments, and the effect of prior PPI use (past vs. current) and treatment duration (<30 and 30−365 days vs. ≥365 days) on incident migraines was evaluated using logistic regression. In past and current PPI users, prior PPI use raised the likelihood of migraines (adjusted odds ratio [95% confidence interval]: 2.56 [2.36−2.79] and 4.66 [4.29−5.06], respectively). Participants who used PPI for <30, 30−365, or ≥365 days exhibited high odds of migraines (2.49 [2.29−2.72], 4.41 [4.05−4.79], and 4.14 [3.77−4.54], respectively). Incident migraines with or without aura also increased independently of PPI use history or duration. In summary, prior PPI use, irrespective of the elapsed time since use and the duration of use, is possibly associated with incident migraines with or without aura.

The Janus-like Association between Proton Pump Inhibitors and Dementia

Early pharmacoepidemiological studies suggested that Proton Pump Inhibitors (PPIs) might increase the risk of Alzheimer’s Disease (AD) and non-AD related dementias. These findings were supported by preclinical studies, specifically stressing the proamyloidogenic and indirect anticholinergic effects of PPIs. However, further large-scale pharmacoepidemiological studies showed inconsistent results on the association between PPIs and dementia. Pharmacodynamically, these findings might be related to the LXR/RXR-mediated amyloid clearance effect and anti-inflammatory action of PPIs. Further aspects that influence PPI effects on AD are related to patient-specific pharmacokinetic and pharmacogenomic characteristics. In conclusion, a personalized (individualized) medicinal approach is necessary to model and predict the potential harmful or beneficial effects of PPIs in AD and non-AD-related dementias in the future.

Emerging biogenesis technologies of extracellular vesicles for tissue regenerative therapeutics

Extracellular vesicles (EVs), including exosomes, carry the genetic packages of RNA, DNA, and proteins and are heavily involved in cell-cell communications and intracellular signalings. Therefore, EVs are spotlighted as therapeutic mediators for the treatment of injured and dysfunctional tissues as well as biomarkers for the detection of disease status and progress. Several key issues in EVs, including payload content and bioactivity, targeting and bio-imaging ability, and mass-production, need to be improved to enable effective therapeutics and clinical translation. For this, significant efforts have been made recently, including genetic modification, biomolecular and chemical treatment, application of physical/mechanical cues, and 3D cultures. Here we communicate those recent technological advances made mainly in the biogenesis process of EVs or at post-collection stages, which ultimately aimed to improve the therapeutic efficacy in tissue healing and disease curing and the possibility of clinical translation. This communication will help tissue engineers and biomaterial scientists design and produce EVs optimally for tissue regenerative therapeutics.

No association between proton pump inhibitor use and risk of dementia: Evidence from a meta-analysis

BACKGROUND AND AIM

A growing body of literature suggests the association between dementia risk and proton pump inhibitor (PPI) use. Therefore, we aimed to investigate the association between PPI use and dementia risk.

METHODS

An extensive literature search was performed in PubMed, Embase, and Cochrane till March 31, 2019. All the studies (cohort and case-control) assessing the association between PPI use and dementia risk were eligible for inclusion. Articles were selected based on the screening of title and abstract, data were extracted, and risk of bias was assessed using Newcastle-Ottawa scale. The primary outcome was pooled risk of dementia among PPI user as compared with non-PPI user. Secondary outcomes include dementia risk based on subgroups. Statistical analysis was performed using review manager software.

RESULTS

Twelve studies (eight cohort and four case-control) were found to be eligible for inclusion. Majority of the studies were of high quality. Dementia was diagnosed based on International Classification of Diseases 9/10 codes in majority of the included studies. PPI use was not associated with the dementia risk, with a pooled relative risk (RR) of 1.05 (95% confidence interval [CI]: 0.96-1.15), P = 0.31. Subgroup analysis based on study design (cohort: P = 0.14; case-control: P = 0.14), sex (RR 1.25 [95% CI: 0.97-1.60], P = 0.08), histamine 2 receptor antagonist blockers (P = 0.93), and Alzheimer's disease (RR 1.00 [95% CI: 0.91-1.09], P = 0.93) revealed no significant association between PPI use and dementia risk.

CONCLUSION

We found no significant association between PPI use and the risk of dementia or Alzheimer's disease.

Proton Pump Inhibitors and Dementia: Physiopathological Mechanisms and Clinical Consequences

Alzheimer's disease (AD) is the most common type of dementia, mainly encompassing cognitive decline in subjects aged ≥65 years. Further, AD is characterized by selective synaptic and neuronal degeneration, vascular dysfunction, and two histopathological features: extracellular amyloid plaques composed of amyloid beta peptide (Aβ) and neurofibrillary tangles formed by hyperphosphorylated tau protein. Dementia and AD are chronic neurodegenerative conditions with a complex physiopathology involving both genetic and environmental factors. Recent clinical studies have shown that proton pump inhibitors (PPIs) are associated with risk of dementia, including AD. However, a recent case-control study reported decreased risk of dementia. PPIs are a widely indicated class of drugs for gastric acid-related disorders, although most older adult users are not treated for the correct indication. Although neurological side effects secondary to PPIs are rare, several preclinical reports indicate that PPIs might increase Aβ levels, interact with tau protein, and affect the neuronal microenvironment through several mechanisms. Considering the controversy between PPI use and dementia risk, as well as both cognitive and neuroprotective effects, the aim of this review is to examine the relationship between PPI use and brain effects from a neurobiological and clinical perspective.

Expression and role of V1A subunit of V-ATPases in gastric cancer cells

BACKGROUND

Vacuolar-ATPases (V-ATPases) play an important role in maintaining a relatively neutral pHi (internal pH) and are responsible for the progression of cancer. V-ATPases contain different subunits and few studies have been conducted on subunit V1A. This study aimed to investigate the gene expression of V1A subunit of V-ATPases in gastric cancer tissues and explore its role in the progression and prognosis of gastric cancer.

METHODS

The protein expressions of the V1A subunit of V-ATPase gene in 100 normal gastric specimens and 100 gastric cancer tissues were determined by immunohistochemistry. The role of V1A subunit of V-ATPases was studied using a specific small interfering RNA (siRNA).

RESULTS

The positive expression rate of the V1A subunit of V-ATPases was 76 % in gastric cancer tissue samples, much higher than that in normal tissue samples (30 %, P < 0.05), and was correlated with histological grade (P = 0.001), lymph node metastasis (P = 0.002), TNM (P = 0.040), and vascular invasion (P = 0.010), but not with patient age, sex, depth of tumor invasion, tumor size, or histological type. The median overall survival times of 76 patients who had positive staining for tumor cell V1A subunit of V-ATPases and 24 patients who had negative staining were 31.7 and 59.2 months, respectively. When the expression of V1A subunit was knocked down using siRNA, the proliferation and invasion of gastric cancer cells in vitro were significantly inhibited.

CONCLUSIONS

V1A subunit of V-ATPases can be a prognostic indicator for poor outcome and is a therapeutic target in gastric cancer.

Vas deferens neuro-effector junction: from kymographic tracings to structural biology principles

The vas deferens is a simple bioassay widely used to study the physiology of sympathetic neurotransmission and the pharmacodynamics of adrenergic drugs. The role of ATP as a sympathetic co-transmitter has gained increasing attention and furthered our understanding of its role in sympathetic reflexes. In addition, new information has emerged on the mechanisms underlying the storage and release of ATP. Both noradrenaline and ATP concur to elicit the tissue smooth muscle contractions following sympathetic reflexes or electrical field stimulation of the sympathetic nerve terminals. ATP and adenosine (its metabolic byproduct) are powerful presynaptic regulators of co-transmitter actions. In addition, neuropeptide Y, the third member of the sympathetic triad, is an endogenous modulator. The peptide plus ATP and/or adenosine play a significant role as sympathetic modulators of transmitter's release. This review focuses on the physiological principles that govern sympathetic co-transmitter activity, with special interest in defining the motor role of ATP. In addition, we intended to review the recent structural biology findings related to the topology of the P2X1R based on the crystallized P2X4 receptor from Danio rerio, or the crystallized adenosine A2A receptor as a member of the G protein coupled family of receptors as prototype neuro modulators. This review also covers structural elements of ectonucleotidases, since some members are found in the vas deferens neuro-effector junction. The allosteric principles that apply to purinoceptors are also reviewed highlighting concepts derived from receptor theory at the light of the current available structural elements. Finally, we discuss clinical applications of these concepts.

Proton pump inhibition increases rapid eye movement sleep in the rat

Increased bodily CO₂ concentration alters cellular pH as well as sleep. The proton pump, which plays an important role in the homeostatic regulation of cellular pH, therefore, may modulate sleep. We investigated the effects of the proton pump inhibitor “lansoprazole” on sleep-wakefulness. Male Wistar rats were surgically prepared for chronic polysomnographic recordings. Two different doses of lansoprazole (low: 1 mg/kg; high: 10 mg/kg) were injected intraperitoneally in the same animal (n = 7) and sleep-wakefulness was recorded for 6 hrs. The changes in sleep-wakefulness were compared statistically. Percent REM sleep amount in the vehicle and lansoprazole low dose groups was 9.26 ± 1.03 and 9.09 ± 0.54, respectively, which increased significantly in the lansoprazole high dose group by 31.75% (from vehicle) and 34.21% (from low dose). Also, REM sleep episode numbers significantly increased in lansoprazole high dose group. Further, the sodium-hydrogen exchanger blocker “amiloride” (10 mg/kg; i.p.) (n = 5) did not alter sleep-wake architecture. Our results suggest that the proton pump plays an important role in REM sleep modulation and supports our view that REM sleep might act as a sentinel to help maintain normal CO₂ level for unperturbed sleep.

Vacuolar-type H+-ATPase V1A subunit is a molecular partner of Wolfram syndrome 1 (WFS1) protein, which regulates its expression and stability

Wolfram syndrome is an autosomal recessive disorder characterized by neurodegeneration and diabetes mellitus. The gene responsible for the syndrome (WFS1) encodes an endoplasmic reticulum (ER)-resident transmembrane protein that also localizes to secretory granules in pancreatic beta cells. Although its precise functions are unknown, WFS1 protein deficiency affects the unfolded protein response, intracellular ion homeostasis, cell cycle progression and granular acidification. In this study, immunofluorescent and electron-microscopy analyses confirmed that WFS1 also localizes to secretory granules in human neuroblastoma cells. We demonstrated a novel interaction between WFS1 and the V1A subunit of the H(+) V-ATPase (proton pump) by co-immunoprecipitation in human embryonic kidney (HEK) 293 cells and with endogenous proteins in human neuroblastoma cells. We mapped the interaction to the WFS1-N terminal, but not the C-terminal domain. V1A subunit expression was reduced in WFS1 stably and transiently depleted human neuroblastoma cells and depleted NT2 (human neuron-committed teratocarcinoma) cells. This reduced expression was not restored by adenoviral overexpression of BiP (immunoglobulin-binding protein) to correct the ER stress. Protein stability assays demonstrated that the V1A subunit was degraded more rapidly in WFS1 depleted neuroblastoma cells compared with wild-type; however, proteosomal inhibition did not restore the expression of the V1A subunit. Cell cycle assays measuring p21(cip) showed reduced levels in WFS1 depleted cells, and an inverse association between p21(cip) expression and apoptosis. We conclude that WFS1 has a specific interaction with the V1A subunit of H(+) ATPase; this interaction may be important both for pump assembly in the ER and for granular acidification.