Lactic Acidosis Together with GM-CSF and M-CSF Induces Human Macrophages toward an Inflammatory Protumor Phenotype.

In established tumors, tumor-associated macrophages (TAM) orchestrate nonresolving cancer-related inflammation and produce mediators favoring tumor growth, metastasis, and angiogenesis. However, the factors conferring inflammatory and protumor properties on human macrophages remain largely unknown. Most solid tumors have high lactate content. We therefore analyzed the impact of lactate on human monocyte differentiation. We report that prolonged lactic acidosis induces the differentiation of monocytes into macrophages with a phenotype including protumor and inflammatory characteristics. These cells produce tumor growth factors, inflammatory cytokines, and chemokines as well as low amounts of IL10. These effects of lactate require its metabolism and are associated with hypoxia-inducible factor-1α stabilization. The expression of some lactate-induced genes is dependent on autocrine M-CSF consumption. Finally, TAMs with protumor and inflammatory characteristics (VEGFhigh CXCL8+ IL1ß+) are found in solid ovarian tumors. These results show that tumor-derived lactate links the protumor features of TAMs with their inflammatory properties. Treatments that reduce tumor glycolysis or tumor-associated acidosis may help combat cancer.

The association of promoter gene polymorphisms of the tumor necrosis factor-α and interleukin-10 with severity of lactic acidosis during liver transplantation surgery.

BACKGROUND: Orthotopic liver transplantation (OLT) is a major operation, causing cytokine release and other inflammatory responses that can contribute to postreperfusion syndrome occurrence. During the systemic inflammatory response syndrome, increased lactate levels result from excessive cytokine production despite normal oxygen delivery and carbohydrate metabolism. The goal of the study was to determine the relationship between genetic polymorphisms in interleukin (IL)-10 (-1082G/A) or tumor necrosis factor (TNF)-α (-376 G/A) and lactate levels in patients during OLT surgery. PATIENTS AND METHODS: This prospective observational study in 40 consecutive adult patients who underwent OLT documented lactic acid levels at 5 times: Immediately after induction of anesthesia, at the end of the pre-anhepatic phase, at the end of the anhepatic phase, 1 hour after reperfusion, and at the end of surgery. Polymerase chain reaction (PCR; RFLP methodology) was used to examine IL-10 (-1082G/A) and TNF-α (-376 G/A) gene polymorphisms. RESULTS: Carriers of the IL-10/TNF-α genotype combination GG/GG showed significantly different changes in lactate levels at 1 hour after reperfusion and at the end of surgery. Lactate levels were significantly higher among patients heterozygous for TNF-α (AG genotype) compared with patients homozygous for TNF-α (GG genotype) at same times. In contrast, there was no significant difference among IL-10 polymorphic genotypes (-1082G/A). CONCLUSION: Genetic factors play a role in the development of lactic acidosis after OLT. IL-10 (-1082G/A) and TNF-α (-376 G/A) gene polymorphisms could influence the variability of lactate levels after liver transplantation surgery.

Moderate hypothermia suppressed excessive generation of superoxide anion radical and inflammatory reactions in blood and liver in heatstroke: laboratory study in rats.

Abstract The study was performed to demonstrate superoxide radical (O(2).-) generation, systemic inflammation and liver injury caused by heatstroke and to reveal suppressive effects of moderate hypothermia. Heatstroke was defined as achieving pharyngeal temperature of 40 degrees C with arterial pressure reduction. Heatstroke rats were divided to four groups by the temperature after the onset; 40 degrees C, 37 degrees C, 32 degrees C and sham-treated with 37 degrees C. O(2).- current was measured continuously in the right atrium using an electrochemical O(2).- sensor. The O(2).- current increased in all groups except for the sham-treated group during the induction. After the onset of heatstroke, the O(2).- current was suppressed with temperature-dependency. Plasma and liver high-mobility group box 1, intercellular adhesion molecule-1, plasma aspartate aminotransferase and alanine aminotransferase were also suppressed with the suppression of O(2).- generation. Therefore, excessive O(2).- generation might be a key factor in heatstroke and the suppression with moderate hypothermia would be a therapeutic modality.

Lactic acid and acidification inhibit TNF secretion and glycolysis of human monocytes.

High concentrations of lactic acid (LA) are found under various pathophysiological conditions and are accompanied by an acidification of the environment. To study the impact of LA on TNF secretion, human LPS-stimulated monocytes were cultured with or without LA or the corresponding pH control. TNF secretion was significantly suppressed by low concentrations of LA (< or = 10 mM), whereas only strong acidification had a similar effect. This result was confirmed in a coculture model of human monocytes with multicellular tumor spheroids. Blocking synthesis of tumor-derived lactate by oxamic acid, an inhibitor of lactate dehydrogenase, reversed the suppression of TNF secretion in this coculture model. We then investigated possible mechanisms underlying the suppression. Uptake of [3-(13)C]lactate by monocytes was shown by hyphenated mass spectrometry. As lactate might interfere with glycolysis, the glycolytic flux of monocytes was determined. We added [1,2-(13)C(2)]glucose to the culture medium and measured glucose uptake and conversion into [2,3-(13)C(2)]lactate. Activation of monocytes increased the glycolytic flux and the secretion of lactate, whereas oxygen consumption was decreased. Addition of unlabeled LA resulted in a highly significant decrease in [2,3-(13)C(2)]lactate secretion, whereas a mere corresponding decrease in pH exerted a less pronounced effect. Both treatments increased intracellular [2,3-(13)C(2)]lactate levels. Blocking of glycolysis by 2-deoxyglucose strongly inhibited TNF secretion, whereas suppression of oxidative phosphorylation by rotenone had little effect. These results support the hypothesis that TNF secretion by human monocytes depends on glycolysis and suggest that LA and acidification may be involved in the suppression of TNF secretion in the tumor environment.

The influence of HIV infection and antiretroviral therapy on the mitochondrial membrane potential of peripheral mononuclear cells.

OBJECTIVES: Clinical disorders occurring in HIV-infected patients on antiretroviral therapy (ART) have been linked to mitochondrial dysfunction, for example, lactic acidosis and lipodystrophy. Mitochondrial membrane potential (delta psi m) is the most direct measure of the state of energization of the mitochondria. We analysed delta psi m, of peripheral blood mononuclear cells (PBMCs) in HIV-negative, healthy subjects (n=8), HIV-infected, treatment-naive patients (n=30), and HIV-infected patients on ART (n=58). The influence of ART was analysed in six patients who started their first regimen. METHODS: The delta psi m of PBMC was measured by flow cytometry using the dye JC-1. RESULTS: The delta psi m was significantly lower in HIV-infected patients than in HIV-negative controls. This difference was detected in both treated (P = 0.0001) and untreated patients (P = 0.001). The delta psi m of PBMCs was highly correlated with CD4+ T-cell count in therapy-naive patients (P = 0.002, r = 0.546) and in treated patients (P = 0.028, r = 0.288). The delta psi m increased significantly in therapy-naive patients after starting ART (P = 0.001). Patients with lipoatrophy had significantly lower delta psi m than patients without lipodystrophy or with lipohypertrophy (P = 0.023). CONCLUSIONS: In HIV-infected persons delta psi m is significantly reduced. Patients with lipoatrophy have significantly reduced delta psi m. This is the first study showing that the delta psi m of PBMCs is highly correlated with CD4+ T-cell count in HIV infection.

Complement activation during hemorrhagic shock and resuscitation in swine.

Activation of the complement (C) cascade is known to play a key role in the adverse immune consequences of hemorrhagic trauma with subsequent shock and resuscitation. However, it is not clear whether hypovolemia per se, without trauma and resuscitation, can also lead to C activation. To address this question, we studied the presence, kinetics, and cause of C activation in a porcine model of hemorrhagic shock and resuscitation in the absence of trauma. Pigs were bled to and kept at 35 mmHg for 90 min, followed by hypotensive resuscitation with different fluids and, finally, with shed blood. The animals developed severe lactic acidosis between 30 and 90 min, which was accompanied by a trend for initial rise and subsequent 40% drop of CH50/mL, indicating massive C activation even before resuscitation, i.e., before reperfusion damage could have occurred. Resuscitation with plasma expanders caused 20% additional C consumption, whereas whole blood raised CH50/mL. Plasma C5a decreased initially and then significantly increased at 60 and 180 min, whereas thromboxane B2 showed a 3-fold increase at 30 and 60 min. Plasma LPS was also increased above baseline at 90 and 180 min. In in vitro studies with pig blood, spontaneous C5a formation, as well as zymosan-induced C consumption, was significantly enhanced under the conditions of lactic acidosis. Our data suggest that lactic acidosis, endotoxemia, and possibly other ischemia-related tissue alterations act in a vicious cycle in inducing C activation and, hence, aggravation of shock. The biphasic course of CH50/mL and C5a changes may reflect yet unrecognized physiological responses to hemorrhage-related C activation.

Immunization with Streptococcus bovis protects against lactic acidosis in sheep.

Lactic acidosis is a gastrointestinal disorder resulting from the rapid overgrowth of lactic acid-producing bacteria when ruminants are suddenly introduced to grain feed. The present study has investigated the ability of live and killed bacterial vaccines to reduce lactic acidosis in sheep, via a stimulation of specific antibody production against lactic acid-producing bacteria. Forage-fed sheep were immunized with live or killed Streptococcus bovis Sb-5 vaccine, with or without adjuvant, via intramuscular injection. After the primary immunization, three boosters were given at 2-4 week intervals. Sheep were subsequently challenged by a sudden switch to a grain-based diet. Following challenge, vaccinated sheep maintained significantly higher feed intake, and had higher rumen pH, lower L-lactate concentrations, and less severe diarrhoea scores than non-vaccinated control sheep. Higher rumen pH, lower mortality and less severe diarrhoea were found in the animals immunized with live vaccine compared to the animals immunized with killed vaccines. Significant increases in mucosal and systemic antibody responses were observed after boosting; the S. bovis-specific antibody concentrations were significantly higher in samples of saliva, rumen fluid and serum from sheep immunized with live vaccine than with killed vaccines. These results demonstrate that lactic acidosis can be reduced by immunization against S. bovis, and that live Sb-5 vaccine is effective in invoking mucosal as well as systemic antibody responses.

Immunisation against lactic acidosis in cattle.

The present study was designed to investigate the efficacy of control of lactic acidosis by immunisation against lactic acid-producing bacteria, Streptococcus bovis and Lactobacillus. Ten steers were allocated to two treatment groups. One group was immunised with a vaccine containing S. bovis (strain Sb-5) and Lactobacillus (LB-27) cells, and the other was a non-immunised control group. The vaccine, using Freund's complete adjuvant for primary immunisation and Freund's incomplete adjuvant for boosters, was administered intramuscularly. After primary immunisation, boosters were given at 2 to 4 week intervals. Both anti- S. bovis and anti- Lactobacillus IgG levels in saliva increased significantly (P < 0.01) after the 1st booster which were lower (P < 0.05) than the IgG levels after the 2nd and 3rd boosters, but were not significantly different (P > 0.05) from the IgG levels prior to a grain challenge (after the 4th booster). There were positive correlations between the anti- S.bovis and anti- Lactobacillus IgG in serum and saliva. Compared with the control group, steers in the immunised group had higher (P < 0.05) feed intakes, lower (P < 0.05) rumen concentrations of lactate and lower numbers of S. bovis and Lactobacillus. Three of the control animals were withdrawn from the grain challenge due to their rumen pH persisting below 5.2, while only one animal in the immunised group was withdrawn. These results suggest that the risk of lactic acidosis can be reduced by immunisation against S. bovis and Lactobacillus.

In vitro activation of complement and contact system by lactic acidosis.

The activation of complement and contact systems occurs in reperfusion injuries with initial tissue hypoxia, and lactic acidosis such as mycardial infarction and birth asphyxia. The aim of our experiment was the formal proof of activation by sole lactic acidosis. Lactic acid was added to blood and plasma samples from 10 healthy volunteers. C5a and factor XIIa were measured by EIA after incubation at 37 degrees C for 1 h. Both concentrations increased (P < 0.0001 by Friedman analysis) in blood and plasma samples with increasing amount of added lactic acid. Lactic acidosis can activate C5 from the complement system and factor XII from the contact system directly, even in the absence of cellular components.