Abnormal Acidification Research Articles

Enhanced autophagic clearance of amyloid-β via histone deacetylase 6-mediated V-ATPase assembly and lysosomal acidification protects against Alzheimer's disease in vitro and in vivo.

JOURNAL/nrgr/04.03/01300535-202509000-00025/figure1/v/2024-11-05T132919Z/r/image-tiff Recent studies have suggested that abnormal acidification of lysosomes induces autophagic accumulation of amyloid-β in neurons, which is a key step in senile plaque formation. Therefore, restoring normal lysosomal function and rebalancing lysosomal acidification in neurons in the brain may be a new treatment strategy for Alzheimer's disease. Microtubule acetylation/deacetylation plays a central role in lysosomal acidification. Here, we show that inhibiting the classic microtubule deacetylase histone deacetylase 6 with an histone deacetylase 6 shRNA or thehistone deacetylase 6 inhibitor valproic acid promoted lysosomal reacidification by modulating V-ATPase assembly in Alzheimer's disease. Furthermore, we found that treatment with valproic acid markedly enhanced autophagy, promoted clearance of amyloid-β aggregates, and ameliorated cognitive deficits in a mouse model of Alzheimer's disease. Our findings demonstrate a previously unknown neuroprotective mechanism in Alzheimer's disease, in which histone deacetylase 6 inhibition by valproic acid increases V-ATPase assembly and lysosomal acidification.

Esophageal Manometry, pH Testing, Endoscopy, and Videofluoroscopy in Patients With Globus Sensation

Combine techniques commonly employed in the clinical workup of patients with isolated globus sensation to identify the most common pharyngoesophageal abnormality. The primary aim was to retrospectively review high-resolution manometry, pH probe testing, contrast videofluoroscopy, and endoscopy studies in patients with a primary complaint of globus sensation. The specific hypothesis was esophageal high-resolution manometry identifies the most significant proportion of abnormalities compared to all other modalities. Retrospective cohort study. An inclusive retrospective chart review was performed for patients evaluated between 2009 and 2016 with the primary complaint of globus sensation. Age at testing, self-identified gender, associated diagnoses, and results from each modality were collected. Descriptive statistics and pairwise comparisons were performed as well as sensitivity and specificity calculations. One hundred seventy-two patients met inclusion criteria. The cohort had an age range of 22.7 to 88.5 years and was predominantly female. Esophageal manometry identified abnormalities in 62.8% of patients, and pH testing identified abnormal acidification in approximately 20%. The esophagram identified abnormalities in 24% of patients, and esophagogastroduodenoscopy identified abnormalities in 22%. Modified barium swallows were normal in 93% of patients. Measures of sensitivity and specificity of other modalities were poor compared to esophageal manometry and pH testing. Patients with isolated globus sensation have evidence of esophageal dysmotility and laryngopharyngeal and gastroesophageal reflux disease in high proportions. Esophageal high-resolution manometry testing identifies the greatest proportion of abnormalities of the investigated modalities. 4 Laryngoscope, 130:2120-2125, 2020.

TNF-α Suppresses Autophagic Flux in Acinar Cells in IgG4-Related Sialadenitis

IgG4-related sialadenitis (IgG4-RS) is a newly recognized immune-mediated systemic fibroinflammatory disease that affects salivary glands and leads to hyposalivation. Tumor necrosis factor–α (TNF-α) is a critical proinflammatory cytokine involved in several salivary gland disorders, but its role and mechanism regarding acinar cell injury in IgG4-RS are unknown. Here, we found that TNF-α level was significantly increased in serum and submandibular gland (SMG) of patients and that serum TNF-α level was negatively correlated with saliva flow rate. Ultrastructural observations of IgG4-RS SMGs revealed accumulation of large autophagic vacuoles, as well as dense fibrous bundles, decreased secretory granules, widened intercellular spaces, swollen mitochondria, and expanded endoplasmic reticulum. Expression levels of LC3 and p62 were both increased in patients’ SMGs. TNF-α treatment led to elevated levels of LC3II and p62 in both SMG-C6 cells and cultured human SMG tissues but did not further increase their levels when combined with bafilomycin A1 treatment. Moreover, transfection of Ad-mCherry-GFP-LC3B in SMG-C6 cells confirmed the suppression of autophagic flux after TNF-α treatment. Immunofluorescence imaging revealed that costaining of LC3 and the lysosomal marker LAMP2 was significantly decreased in patients, TNF-α–treated SMG-C6 cells, and cultured human SMGs, indicating a reduction in autophagosome-lysosome fusion. Furthermore, the ratio of pro/mature cathepsin D was elevated in vivo, ex vivo, and in vitro. TNF-α also appeared to induce abnormal acidification of lysosomes in acinar cells, as assessed by lysosomal pH and LysoTracker DND-26 fluorescence intensity. In addition, TNF-α treatment induced transcription factor EB (TFEB) redistribution in SMG-C6 cells, which was consistent with the changes observed in IgG4-RS patients. TNF-α increased the phosphorylation of extracellular signal–regulated kinase (ERK) 1/2, and inhibition of ERK1/2 by U0126 reversed TNF-α–induced TFEB redistribution, lysosomal dysfunction, and autophagic flux suppression. These findings suggest that TNF-α is a key cytokine related to acinar cell injury in IgG4-RS through ERK1/2-mediated autophagic flux suppression.

How to find and diagnose a CDG due to defective N‐glycosylation

The group of Congenital Disorders of Glycosylation (CDG) is expanding rapidly since the first clinical description of the N-glycosylation defect PMM2-CDG (CDG-Ia) in 1980 (Jaeken et al. 1980). Since then, more than 50 defects have been identified in protein N-glycosylation (some of them also associated with an O-glycosylation defect), in protein O-glycosylation only and in lipid glycosylation (GPI anchor and glycosphingolipid synthesis). Here, we provide a simple approach to the clinical, biochemical and genetic diagnosis of CDG due to a N-glycosylation defect (including combined N- and O-glycosylation defects).

MUSCULAR pH AND RELATED TRAITS IN RABBITS : A REVIEW

After reviewing muscular biology and general relationships between muscular physico-chemistry and meat quality, this review analyses the variations in muscular pH and related traits in rabbits. Among biological factors (muscle, age, genotype, family), muscle factor is the most important. lt determines the differences in ultimate pH (pHu) between muscles, which can reach 0.7 units and which are due to differences in the fibre typology. lncrease in glycolytic metabolism during muscle growth is accompanied by pHu lowering; its variation depends on the precocity of muscle development. Comparative studies of breeds do not show any evidence of differences in pH above 0.2 units; no breed presents abnormal acidification or pHu kinetics, which might entail anomalies in Water Holding Capacity or other qualitative traits in meat. Wlthln breed, the existence of correlations between pHu and growth characteristics may lead to a reduction in meat quality when strains are selected for weight productivity. The effect of dietary faetors is relatively small. When they can be detected, pH variations mostly correspond to modifications in growth rate. Thus the pHu of meat is lowered when growth is stimulated by a high level of nutrition or a high protein content. Slaughter faetors have a marked influence on muscular pH. Transport leads to a noticeable rise in pHu, a result of ante mortem depletion of glycogenic reserves; when subjected to prolonged stress, meat is darker and has a higher water holding capacity. Electroanaesthesia accelerates muscular acidification without modifying pHu. careass ehllling slows down the physico-chemical processes of rigor mortis: it slows down the fall in pH and reduces the intensity of sarcomere retraction. Even when chilling is intense, in spite of sorne contradictions in published literature, the phenomenon of cold shortening does not seem to be of major significance in rabbits. During meat storage in refrigerated form, after a certain latency period, the maturation processes are witnessed by de-amination of the proteins and thus by a raised pH. Freezing slows down this process, but does not avoid a rise in pH after several months in storage.

Reflux Masquerader: Acute Helicobacter pylori Infection in Neonates and Infants

Reflux Masquerader: Acute <i>Helicobacter pylori</i> Infection in Neonates and Infants

Stratum Corneum Acidification Is Impaired in Moderately Aged Human and Murine Skin

Aged skin commonly is afflicted by inflammatory skin diseases or xerosis/eczema that could be triggered or exacerbated by impaired epidermal permeability barrier homeostasis. This defect is linked to reduced epidermal lipid synthesis in humans and in mice of advanced age (i.e., >75 years in human or >18-24 months in mice). We now report that barrier defects in moderately aged humans (50-80 years) or analogously aged mice (12-15 months) are linked instead to defective stratum corneum (SC) acidity. In moderately aged mouse epidermis, we find that abnormal acidification, in turn, is linked to decreased Na+/H+ antiporter (NHE1) expression. Decreased NHE1 levels lead to increased SC pH, which results in defective lipid processing and delayed maturation of lamellar membranes, due to suboptimal activation of the pH-sensitive essential, lipid-processing enzyme, beta-glucocerebrosidase. Conversely, impaired SC integrity in moderately aged mice is due to increased pH-dependent activation of serine proteases, leading to premature degradation of corneodesmosomes. These abnormalities were normalized by exogenously acidifying the SC, suggesting a basis for the well-known acidification therapies that are widely used to treat the pathologic xerosis/eczema seen in moderately aged humans.

The BEACH Protein LvsB Is Localized on Lysosomes and Postlysosomes and Limits Their Fusion with Early Endosomes

The Chediak-Higashi syndrome (CHS) is a genetic disorder caused by the loss of the BEACH protein Lyst. Impaired lysosomal function in CHS patients results in many physiological problems, including immunodeficiency, albinism and neurological problems. Dictyostelium LvsB is the ortholog of mammalian Lyst and is also important for lysosomal function. A knock-in approach was used to tag LvsB with green fluorescent protein (GFP) and express it from its single chromosomal locus. GFP-LvsB was observed on late lysosomes and postlysosomes. Loss of LvsB resulted in enlarged postlysosomes, in the abnormal localization of proton pumps on postlysosomes and their abnormal acidification. The abnormal postlysosomes in LvsB-null cells were produced by the inappropriate fusion of early endosomal compartments with postlysosomal compartments. The intermixing of compartments resulted in a delayed transit of fluid-phase marker through the endolysosomal system. These results support the model that LvsB and Lyst proteins act as negative regulators of fusion by limiting the heterotypic fusion of early endosomes with postlysosomal compartments.

Abnormal Acidification of Melanoma Cells Induces Tyrosinase Retention in the Early Secretory Pathway

In tyrosinase-positive amelanotic melanoma cells, inactive tyrosinase accumulates in the endoplasmic reticulum. Based on studies described here, we propose that aberrant vacuolar proton ATPase (V-ATPase)-mediated proton transport in melanoma cells disrupts tyrosinase trafficking through the secretory pathway. Amelanotic but not melanotic melanoma cells or normal melanocytes display elevated proton export as observed by the acidification of the extracellular medium and their ability to maintain neutral intracellular pH. Tyrosinase activity and transit through the Golgi were restored by either maintaining the melanoma cells in alkaline medium (pH 7.4-7.7) or by restricting glucose uptake. The translocation of tyrosinase out of the endoplasmic reticulum and the induction of cell pigmentation in the presence of the ionophore monensin or the specific V-ATPase inhibitors concanamycin A and bafilomycin A1 supported a role for V-ATPases in this process. Because it was previously shown that V-ATPase activity is increased in solid tumors in response to an acidified environment, the appearance of hypopigmented cells in tyrosinase-positive melanoma tumors may indicate the onset of enhanced glycolysis and extracellular acidification, conditions known to favor metastatic spread and resistance to weak base chemotherapeutic drugs.

NIH conference. Recent advances in chronic granulomatous disease.

Chronic granulomatous disease represents a group of disorders of phagocytic cell oxidative metabolism involving recurrent infections with catalase-positive microorganisms and chronic inflammation. Genetic heterogeneity and phagocyte abnormalities, including enzyme deficiencies, abnormal elicited membrane potential changes, abnormal acidification of the phagocytic vacuole, and deficiencies of an electron transport cascade, have been associated with its pathogenesis. In addition, recently we have shown abnormal neutrophil C3b-receptor expression, antibody-dependent cellular cytotoxicity, and abnormal microtubule metabolism (tyrosinolation of the alpha-chain of tubulin). Fourteen patients with the disease who were followed at the National Institutes of Health had life-threatening infections, on average, once every 9.6 months. In most of the 119 febrile episodes seen in these patients, no infectious agent was found. Retrospective studies indicated that prophylactic antibiotic therapy, particularly with trimethoprim-sulfamethoxazole, significantly prolonged disease-free intervals to greater than 40 months (p less than 0.05). In serious, life-threatening infections, leukocyte transfusions have been used in therapy. Transfused leukocytes localize and persist at infectious sites, and the clinical efficacy of leukocyte transfusions has been suggested.

Renal Acidifying Ability in Subjects with Recurrent Stone Formation

To determine the incidence of an acidification defect in men in whom calcium stones form and its relationship to parathyroid function 120 such patients were given an acute dosage of 0.1 gm. per kg. oral ammonium chloride and circulating immunoreactive parathyroid hormone was determined. The subjects were divided into 2 groups, according to normal or high parathormone levels. Group 1 consisted of 46 men in whom immunoreactive parathyroid hormone was less than or equal to 60 μlEq. per ml. and group 2 consisted of 74 men with immunoreactive parathyroid hormone greater than 60 μlΈq. per ml. Of 8 men in whom the urine failed to acidify to less than a pH of 5.3, 3 were from group 1 and 5 were from group 2. None of the patients had an active urinary tract infection. There was no difference in minimal urine pH among the patients in whom the urine acidified normally regardless of immunoreactive parathyroid hormone. The incidence of abnormal acidification in our population was 6 per cent and all of these patients had the incomplete form of renal tubular acidosis. These findings have important therapeutic implications.