Short-term Acidosis Research Articles

Impact of Acute or Chronic Acidosis and Hypoxia on Gene Expression Patterns in Tumour Cells: Potential Functional Implications.

Tumours often exhibit pronounced hypoxia and hereby extracellular acidosis due to intensified glycolysis. Since metabolic parameters can modulate gene expression, the aim of the study was to analyse changes in gene expression patterns induced by acute (24h) acidosis or hypoxia and also in tumour cells adapted to long-term acidosis (5weeks). Three tumour cell lines (AT1 prostate carcinoma, MCF-7, and MDA-MB-231 breast carcinoma) were exposed to acidosis (pH6.6) or hypoxia (pO2 1.5mmHg) for 24h. For long-term acidosis, AT1 tumour cells were continuously cultured at pH6.6 for 5weeks. Gene expression was examined by total RNA-sequencing and the functional significance was assessed by gene set enrichment analysis using the Gene Ontology database. Under short-term acidosis (24h), AT1 and MCF-7 cells showed comparable changes. 714 genes were acidosis-dependently regulated in AT1 cells (275 up, 439 down), and 221 genes in MCF-7 cells (95 up, 126 down). MDA-MB-231 cells almost did not respond to low pH (13 regulated genes). Hypoxia affected MCF-7 cells the most (1498 regulated genes), whereas fewer genes were regulated in AT1 and MDA-MB-231 cells. Concerning the function of the regulated genes by short-term acidosis, RNA processing, cell cycle regulation, DNA synthesis, and mitochondrial function were negatively affected. Chronic acidosis showed a different picture. In AT1 cells, 1160 genes were differentially expressed (638 up, 522 down) when cells exposed to low pH for 5weeks. The putatively acidosis-induced changes in functions included tissue structural development, RNA processing, and mitochondrial activity. This study shows that both acute and chronic acidosis of tumour cells lead to altered gene expression and thus affect cell function. Long-term acidosis leads to fundamentally different changes, indicating an adaptation process of the tumour cells.

Systematic review of the relationship between rumen acidosis and laminitis in cattle

Laminitis is usually considered a consequence of digestive disorders that reduce ruminal pH. However, it is still not clear the direct relation between low ruminal pH provoked by excessive fast-digesting carbohydrate ingestion and laminitis, considering indicators, signs, and diagnosis aspects. This study aimed to clarify the association between different clinical presentations of laminitis with ruminal acidosis provoked by diet using the systematic review methodology. Three electronic databases were used: ISI Web of Science, PubMed, and Scopus. A total of 339 manuscripts were identified and only 16 were included. Manuscripts were published between 2000 and 2021 in 11 different peer-reviewed journals. Fifteen studies confirmed the occurrence of ruminal acidosis. The main indicators used were ruminal pH and clinical signs, such as anorexia, depression, discomfort and diarrhea. Two of the studies that administered oligofructose to induce acidosis and acute laminitis did not observe clinical signs of laminitis, using lameness score or hooves' sensitivity as an indicator. Various diagnostic methods were used to describe laminitis, like thermography, hoof biopsy, sensitivity test, and visual inspection. Although the variety of laminitis indicators used in the included studies, we evidence the existence of an association between diet (high level of fast-digesting carbohydrates), ruminal acidosis, and acute laminitis, mostly in the short-term acidosis' induction protocols, but the mechanism of action is still not clear.

Acidic Growth Conditions Promote Epithelial-to-Mesenchymal Transition to Select More Aggressive PDAC Cell Phenotypes In Vitro.

Pancreatic Ductal Adenocarcinoma (PDAC) is characterized by an acidic microenvironment, which contributes to therapeutic failure. So far there is a lack of knowledge with respect to the role of the acidic microenvironment in the invasive process. This work aimed to study the phenotypic and genetic response of PDAC cells to acidic stress along the different stages of selection. To this end, we subjected the cells to short- and long-term acidic pressure and recovery to pHe 7.4. This treatment aimed at mimicking PDAC edges and consequent cancer cell escape from the tumor. The impact of acidosis was assessed for cell morphology, proliferation, adhesion, migration, invasion, and epithelial-mesenchymal transition (EMT) via functional in vitro assays and RNA sequencing. Our results indicate that short acidic treatment limits growth, adhesion, invasion, and viability of PDAC cells. As the acid treatment progresses, it selects cancer cells with enhanced migration and invasion abilities induced by EMT, potentiating their metastatic potential when re-exposed to pHe 7.4. The RNA-seq analysis of PANC-1 cells exposed to short-term acidosis and pHe-selected recovered to pHe 7.4 revealed distinct transcriptome rewiring. We describe an enrichment of genes relevant to proliferation, migration, EMT, and invasion in acid-selected cells. Our work clearly demonstrates that upon acidosis stress, PDAC cells acquire more invasive cell phenotypes by promoting EMT and thus paving the way for more aggressive cell phenotypes.

Cancer-associated mesenchymal stroma fosters the stemness of osteosarcoma cells in response to intratumoral acidosis via NF-κB activation.

The role of mesenchymal stem cells (MSC) in osteosarcoma (OS), the most common primary tumor of bone, has not been extensively elucidated. We have recently shown that OS is characterized by interstitial acidosis, a microenvironmental condition that is similar to a wound setting, in which mesenchymal reactive cells are activated to release mitogenic and chemotactic factors. We therefore intended to test the hypothesis that, in OS, acid-activated MSC influence tumor cell behavior. Conditioned media or co-culture with normal MSC previously incubated with short-term acidosis (pH 6.8 for 10 hr, H+ -MSC) enhanced OS clonogenicity and invasion. This effect was mediated by NF-κB pathway activation. In fact, deep-sequencing analysis, confirmed by Real-Time PCR and ELISA, demonstrated that H+ -MSC differentially induced a tissue remodeling phenotype with increased expression of RelA, RelB and NF-κB1, and downstream, of CSF2/GM-CSF, CSF3/G-CSF and BMP2 colony-promoting factors, and of chemokines (CCL5, CXCL5 and CXCL1), and cytokines (IL6 and IL8), with an increased expression of CXCR4. An increased expression of IL6 and IL8 were found only in normal stromal cells, but not in OS cells, and this was confirmed in tumor-associated stromal cells isolated from OS tissue. Finally, H+ -MSC conditioned medium differentially promoted OS stemness (sarcosphere number, stem-associated gene expression), and chemoresistance also via IL6 secretion. Our data support the hypothesis that the acidic OS microenvironment is a key factor for MSC activation, in turn promoting the secretion of paracrine factors that influence tumor behavior, a mechanism that holds the potential for future therapeutic interventions aimed to target OS.

Altered pH gradient at the plasma membrane of osteosarcoma cells is a key mechanism of drug resistance.

Current therapy of osteosarcoma (OS), the most common primary bone malignancy, is based on a combination of surgery and chemotherapy. Multidrug resistance mediated by P-glycoprotein (P-gp) overexpression has been previously associated with treatment failure and progression of OS, although other mechanisms may also play a role. We considered the typical acidic extracellular pH (pHe) of sarcomas, and found that doxorubicin (DXR) cytotoxicity is reduced in P-gp negative OS cells cultured at pHe 6.5 compared to standard 7.4. Short-time (24–48 hours) exposure to low pHe significantly increased the number and acidity of lysosomes, and the combination of DXR with omeprazole, a proton pump inhibitor targeting lysosomal acidity, significantly enhanced DXR cytotoxicity. In OS xenografts, the combination treatment of DXR and omeprazole significantly reduced tumor volume and body weight loss. The impaired toxicity of DXR at low pHe was not associated with increased autophagy or lysosomal acidification, but rather, as shown by SNARF staining, with a reversal of the pH gradient at the plasma membrane (ΔpHcm), eventually leading to a reduced DXR intracellular accumulation. Finally, the reversal of ΔpHcm in OS cells promoted resistance not only to DXR, but also to cisplatin and methotrexate, and, to a lesser extent, to vincristine. Altogether, our findings show that, in OS cells, short-term acidosis induces resistance to different chemotherapeutic drugs by a reversal of ΔpHcm, suggesting that buffer therapies or regimens including proton pump inhibitors in combination to low concentrations of conventional anticancer agents may offer novel solutions to overcome drug resistance.

Longitudinal and cross-sectional effects of C-reactive protein, equilibrated normalized protein catabolic rate, and serum bicarbonate on creatinine and albumin levels in dialysis patients

Background: Loss of muscle mass and hypoalbuminemia each may result in part from either malnutrition, inflammation, or a combination of both. Short-term acidosis increases muscle protein catabolism and inhibits albumin synthesis. Methods: We analyzed albumin and creatinine levels as outcome variables and their association with C-reactive protein (CRP) level, equilibrated normalized protein catabolic rate (enPCR), and serum bicarbonate level as independent variables from laboratory data obtained from patients in the Hemodialysis Study. Analyses controlled for race, sex, age, body mass index, and randomized treatment group. Results: Albumin level correlated with both enPCR and CRP level, but not serum bicarbonate level, in both cross-sectional and longitudinal analyses. Effects of CRP level and enPCR were not linear. Albumin level correlated positively with enPCR for an enPCR less than 1.0 g/kg/d, but not for a greater enPCR, and correlated inversely with CRP level for a CRP level greater than 13 mg/L. Similarly, creatinine level correlated with both enPCR and CRP level. As in the case of albumin level, effects were not linear. Creatinine level correlated positively with enPCR for values less than 1.0 g/kg/d, but not for greater enPCR values. In contrast to albumin level, creatinine level correlated negatively with serum bicarbonate level, even when adjusted for enPCR. Conclusion: Albumin and creatinine levels are independently associated with nutrition (enPCR) and inflammation (CRP level). The cross-sectional relationship with enPCR is apparent only at values less than 1.0 g/kg/d. CRP level is associated with reduced albumin and creatinine values when increased to values greater than 5.6 mg/dL. CRP may be increased to levels associated with increased cardiovascular risk with little or no effect on either serum albumin or creatinine level. Thus, a normal albumin level does not exclude elevated CRP levels.

Transient pre-ischemic acidosis protects the isolated rabbit heart subjected to 30 minutes, but not 60 minutes, of global ischemia.

Adenosine released during brief episodes of ischemia, due to the breakdown of ATP, is thought to be an endogenous mediator of ischemic preconditioning. In this study we sought to determine whether protons, also released from ATP during ischemia, may protect the heart from sustained ischemic insult. Experiments were performed in isolated Langendorff-perfused rabbit hearts. Proton release was simulated by a brief transient episode of preischemic acidosis. Before ischemia all hearts underwent 15 min of preischemic perfusion. Control hearts received 15 min perfusion with normal Krebs-Henseleit buffer (KHB; pH 7.39) while the short-term acidosis (STA) group received 5 min of perfusion with normal KHB followed by 5 min of perfusion with acidic buffer (pH 5.97), and then 5 min of perfusion with normal KHB. Both control and STA groups then underwent 30 min of global ischemia. A second pair of control and STA groups were subjected to 60 min of global ischemia. After global ischemia all hearts received 60 min of reperfusion. The time course of functional recovery after 30 min of ischemia was accelerated in the STA group (i.e., developed pressure in the control and STA groups at 15 min into reperfusion averaged 57 +/- 9 and 74 +/- 3 mmHg, respectively; p < 0.05), and a strong trend towards lower release of creatine kinase after 30 min of global ischemia was observed in the STA group (43 +/- 7 U/g dry tissue in the STA group vs. 76 +/- 15 U/g dry tissue in the control group). However, after 60 min of global ischemia no differences in cardiac function at reperfusion were observed between control and STA groups. Our results indicate that in the isolated rabbit heart, brief acidosis affords protection against 30 min but not against 60 min of global ischemia.

The effects of acidosis on cellular calcium (Ca) regulation in the neonatal rat atrium

THE EFFECTS OF ACIDOSIS ON CELLULAR CALCIUM (Cal REGULATION IN THE NEONATAL RAT ATRIUM Nicholas J. Lodge* and Henrv Gelband, FAAP. Univ. of Miami Sch. of Med., M’iami, FL Acidosis is frequently associated with neonatal cardiac dysfunction. This study examined the effects of acidosis on transmembrane Ca transport systems and intracellular Ca regulation using isotopic Ca (45 Ca). Resting membrane permeability was assessed by measuring Ca uptake into resting tissue. Na-Ca exchange function was estimated from the stimulation of Ca uptake induced by high K/low Na-Tyrode’s solution and Ca channel conductance was estimated from the stimulation of Ca uptake induced by the Ca agonist Bay K 8644, which acts on the channel. Resting tissue Ca content was also measured. Extracel lular 45 Ca was displaced by “washing” tissues with Tyrode’s solution containing 6.8 mM Ca/5 mM EGTA for 45 mins in order to allow resolution of cellular 45 Ca f Iuxes. Acidosis (pH 6.85 for up to 1 hour) failed to significantly alter any of the fol:I,Will,: resting men,hrane permeability (“=I6 atria per time point), high K/low Na induced Ca uptake (n=12) and resting tissue Ca content (n=l6). Bay K 8644induced Ca uptake was similarly unaffected (10 mins acidosis, n=12). When tissues were allowed to equilibrate with acidotic medium for 1 hour the 45 Ca labelled tissue Ca content was lower than control (n=12). This reduction became significant after 3 l/2 hours of 45 Ca Iabelling in acidotic medium (n=12; p< 0.01). Our results suggest that resting membrane permeability, NaCa exchange and the Ca channel are unaffected by short term acidosis. However, the reduced tissue 45 Ca content seen during I hour and 3 l/2 hours 45 Ca + acidosis label ling (compared with control) indicates that some intracellular Ca regulatory system is being affected.

MATERNAL ACIDOSIS AND FETAL GROWTH RETARDATION

Experience with infants born to mothers suffering from ketoacidosis has suggested that acidosis may be involved in fetal growth retardation (FGR). These studies were designed to determine the effect of acidosis on fetal substrate availability as reflected in altered uterine carbohydrate metabolism. Five pregnant ewes of 90-120 days gestation were chronically prepared by surgical implantation of bilateral electromagnetic uterine artery flow transducers and femoral and uterine vein catheters, and unilateral femoral and cystic artery catheters. Following a 4 day recovery period with optimum maternal nutrition, ammonium chloride solution was continuously infused to produce systemic maternal metabolic acidosis. Whole blood samples for glucose assay and acid-base studies were drawn at hourly intervals for 1-5 hrs in 5 ewes and hourly lactate assay in 1 ewe. Uterine glucose uptake and lactate production were calculated by the Fick equation. A total of 29 infusion studies were completed. The infusions produced no significant alterations in maternal glucose concentrations or uterine blood flow. Samples drawn after 4 hr. of acidosis demonstrated a significant decrease in maternal pH (p<.100), and uterine glucose uptake decreased by 55% (p<.05). Lactate production also decreased. We conclude that short term acidosis may decrease fetal substrate availability and that acidosis may play a significant role in the production of fetal growth retardation.