Therapeutically targeting lymphocyte energy metabolism by high-dose glucocorticoids

[High-dose methylprednisolone with Rituximab and fresh frozen plasma in the treatment of six patients with B-cell lymphoproliferative disorders harboring TP53 abnormalities]

Objective: To investigate whether high-dose methylprednisolone with Rituximab and fresh frozen plasma (HDMP+RTX+FFP) is an effective therapy for patients with B-cell chronic lymphoproliferative disorders (B-CLPD) with TP53 abnormalities. Methods: Six B-CLPD patients with TP53 abnormalities from May 2008 to May 2012 were prospectively enrolled in the study. The patients were treated with HDMP+RTX+FFP for up to 6 cycles. Results: Of the six B-CLPD patients, there were 4 cases of chronic B-cell lymphoproliferative disorders-unclassified (B-CLPD-U) , 1 B-cell prolymphocytic leukemia (B-PLL) and 1 mantle cell lymphoma (MCL) . After a median 3 courses of treatment, 4 patients achieved complete remission (CR) including 3 with undetectable minimal residual disease (MRD(-)) . One patient was evaluated as stable disease (SD) and another one patient was in disease progression (PD) . After a median follow-up of 30 (4-56) months, 2 non-responders progressed quickly and died. All of CR patients survived and no one succumbed to disease progression at the last follow-up. The hematopoietic function was significantly improved after the treatment whereas there was also significant decrease in serum IgA, IgG and IgM levels. All patients showed well tolerance to this regimen. The incidence of myelosuppression was low and adverse events (AE) were mainly neutropenia which did not exceed grade 3 and infection. All AE were controllable. Conclusion: HDMP+RTX+FFP is an effective and relatively tolerable therapy for patients with B-CLPD accompanying with TP53 abnormalities.

Bioenergetics of T cell activation and death in HIV type 1 infection

Regressive morphological lesions, found in peripheral lymphocytes from HIV(+) patients, clearly conflict with normal cycle progression and with the execution of basic housekeeping and immune functions. With these lesions, circulating lymphocytes are destined to spontaneous and energy-independent cell lysis. By means of confocal microscopy and morphometry, we have quantified the rate of circulating T cells that are probably destined to emocatheresis in vivo. This rate includes lymphocytes in which nucleolin fragments have been scattered out of the nuclear region as a result of prelethal alterations in the nuclear membrane permeability. In terms of bioenergetics, these cells show evident anomalies in the energy production machinery that make them unable to carry out ATP-requiring functions. The extent of damaged cell fraction in peripheral blood reflects the frequency with which T lymphocytes leave lymphoid tissue to be cleared in hemocatheretic processes.

The role of high-dose corticosteroids in the treatment of chronic lymphocytic leukemia

INTRODUCTION

Management of refractory chronic lymphocytic leukemia (CLL) represents a major challenge because of the poor prognosis and limited treatment options. While corticosteroids have been used to treat CLL since 1940s, their benefit has never been conclusively proved. Recently, several groups reported use of high-dose corticosteroids (methylprednisolone or dexamethasone) either alone or combined with chemotherapy and/or monoclonal antibodies in relapsed/refractory CLL.

AREAS COVERED

While efficacy of high-dose corticosteroids is excellent including responses in patients with bulky lymphadenopathy or those considered ultra high-risk CLL because of deletion and/or mutation of p53 gene, the duration of response is still unsatisfactory. Combination with monoclonal antibodies seems to improve therapeutic efficacy but no randomized trials have been conducted. For the purpose of this review, a search for terms, high-dose corticosteroids/methylprednisolone/dexamethasone, and chronic lymphocytic leukemia has been performed in PubMed and database of abstracts from American Society of Hematology Meetings.

EXPERT OPINION

High-dose corticosteroids appear to play an important role in the management of highly pretreated relapsed/refractory CLL including patients with massive lymphadenopathy. Myelosuppression is usually limited but infectious toxicity, including increased risk of invasive fungal infections, represents the most dreaded side effects. This therapeutic approach should be further tested within large prospective trials, to optimize efficacy and safety.

TRPM7 regulates quiescent/proliferative metabolic transitions in lymphocytes

A unique property of lymphocytes among all body tissues is their capacity for rapid proliferation in the context of responding to infectious challenges. Lymphocyte proliferation involves a transition from a quiescent metabolic state adjusted to maintain cellular energy homeostasis, to a proliferative metabolic state in which aerobic glycolysis is used to generate energy and biosynthetic precursors necessary for the accumulation of cell mass. Here we show that modulation of TRPM7 channel function in tumor B-lymphocytes directly induces quiescent/proliferative metabolic transitions. As TRPM7 is widely expressed outside of the immune system, our results suggest that TRPM7 may play an active role in regulating metabolic transitions associated with rapid cellular proliferation and malignancy.

Characterization of the metabolic phenotype of chronically activated lymphocytes

Activated lymphocytes proliferate, secrete cytokines, and can make antibodies. Normally activated B and T cells meet the bioenergetic demand for these processes by up-regulating aerobic glycolysis. In contrast, several lines of evidence suggest that pathogenic lymphocytes in autoimmune diseases like lupus meet ATP demands through oxidative phosphorylation. Using (13)C-glucose as a stable tracer, we found that splenocytes from mice with lupus derive the same fraction of lactate from glucose as control animals, suggesting comparable levels of glycolysis and non-oxidative ATP production. However, lupus splenocytes increase glucose oxidation by 40% over healthy control animals. The ratio between pentose phosphate cycle (PPC) activity and glycolysis is the same for each group, indicating that increased glucose oxidation is due to increased activity of the TCA cycle in lupus splenocytes. Repetitive stimulation of cultured human T cells was used to model chronic lymphocyte activation, a phenotype associated with lupus. Chronically activated T cells rely primarily on oxidative metabolism for ATP synthesis suggesting that chronic antigen stimulation may be the basis for the metabolic findings observed in lupus mice. Identification of disease-related bioenergetic phenotypes should contribute to new diagnostic and therapeutic strategies for immune diseases.

Rhabdomyosarcoma cells show an energy producing anabolic metabolic phenotype compared with primary myocytes

BACKGROUND

The functional status of a cell is expressed in its metabolic activity. We have applied stable isotope tracing methods to determine the differences in metabolic pathways in proliferating Rhabdomysarcoma cells (Rh30) and human primary myocytes in culture. Uniformly 13C-labeled glucose was used as a source molecule to follow the incorporation of 13C into more than 40 marker metabolites using NMR and GC-MS. These include metabolites that report on the activity of glycolysis, Krebs' cycle, pentose phosphate pathway and pyrimidine biosynthesis.

RESULTS

The Rh30 cells proliferated faster than the myocytes. Major differences in flux through glycolysis were evident from incorporation of label into secreted lactate, which accounts for a substantial fraction of the glucose carbon utilized by the cells. Krebs' cycle activity as determined by 13C isotopomer distributions in glutamate, aspartate, malate and pyrimidine rings was considerably higher in the cancer cells than in the primary myocytes. Large differences were also evident in de novo biosynthesis of riboses in the free nucleotide pools, as well as entry of glucose carbon into the pyrimidine rings in the free nucleotide pool. Specific labeling patterns in these metabolites show the increased importance of anaplerotic reactions in the cancer cells to maintain the high demand for anabolic and energy metabolism compared with the slower growing primary myocytes. Serum-stimulated Rh30 cells showed higher degrees of labeling than serum starved cells, but they retained their characteristic anabolic metabolism profile. The myocytes showed evidence of de novo synthesis of glycogen, which was absent in the Rh30 cells.

CONCLUSION

The specific 13C isotopomer patterns showed that the major difference between the transformed and the primary cells is the shift from energy and maintenance metabolism in the myocytes toward increased energy and anabolic metabolism for proliferation in the Rh30 cells. The data further show that the mitochondria remain functional in Krebs' cycle activity and respiratory electron transfer that enables continued accelerated glycolysis. This may be a common adaptive strategy in cancer cells.

Sex differences in human lymphocyte Na,K-ATPase as studied by labeled ouabain binding

Lymphocytes Na,K-ATPase is a plasma membrane enzyme that is up-regulated under lymphocytes activation. It is also studied as a model of brain cells Na,K-ATPase. Data about sex-related specificities of the enzyme are not available. The binding of tritium-labelled ouabain to lymphocyte plasma membrane Na,K-ATPase was studied in healthy volunteers of both sexes. The binding interactions were expressed in terms of K(D) and B(Max). The first parameter is related to the affinity of ouabain for the enzyme whereas the second one is related to its density on the cell membrane. Distinct sex-related differences were found. Whereas in males there is a significant direct correlation between the parameters K(D) and B(Max), in females this is not present. However, in females there is a significantly lower K(D) in the 25-37 age range. The latter result probably reflects the expression of subunit variants giving a greater affinity for ouabain. This circumstance may be relevant both to lymphocytes' ability to be activated and to brain function, if one admits that lymphocyte Na,K-ATPase faithfully represents the brain-borne one.

Avicins, a novel plant-derived metabolite lowers energy metabolism in tumor cells by targeting the outer mitochondrial membrane

Avicins are pro-apoptotic, anti-inflammatory molecules with antioxidant effects both in vitro and in vivo. Based on their ability to perturb mitochondrial functions and initiate apoptosis in tumor cells, we chose to study the bioenergetic effects of avicins on tumor cell mitochondria. Avicin-treated Jurkat cells, showed a decrease in the levels of cellular ATP as well as the rate of oxygen consumption. These effects on cellular metabolism appear to be a result of avicin's actions on the outer mitochondrial membrane (OMM). We speculate that avicins might initially inhibit the exchange of metabolites across the OMM leading to its subsequent permeabilization to cytochrome c. This speculation is supported by biophysical studies using lipid bilayers, which suggest that upstream of these effects, avicins target and close the voltage dependent anion channel (VDAC). Closure of VDAC would lead to an overall lowering of the cell energy metabolism, subsequently pushing these cells towards the apoptotic pathway by permeabilization of the OMM and release of cyt-c. Avicins therefore not only represent a novel pharmacological tool for treatment of cancers, but also highlight the influence ancient plant metabolites could have on human health.

G-protein-coupled glucocorticoid receptors on the pituitary cell membrane

Rapid, nongenomic actions of glucocorticoids (GCs) have been well documented, but information about putative membrane receptors that mediate them is scarce. We used fluorescence correlation spectroscopy to search for membrane GC-binding on the mouse pituitary cell line AtT-20. A slowly diffusing fraction (τ3; diffusion constant 3×10-10 cm2 s-1) of fluorescein-labeled dexamethasone on the cell membrane corresponds to fluorescein-dexamethasone binding. Preincubation experiments were performed to test binding specificity: a 500-fold excess of unlabeled dexamethasone abolished subsequent fluorescein-dexamethasone membrane binding from 58±2 (control) to 8±1 (% of τ3, mean ± s.e.m.), the natural ligand corticosterone prevented it partially (29±2), while the sex steroids estradiol (56±4) and progesterone (50±4) and the GC-receptor antagonist RU486 (56±2) had no effect. Preincubation with pertussis toxin resulted in disappearance of the slowest diffusion component (11±4) suggesting association of the receptor with a G-protein. Varying the concentration of fluorescein-dexamethasone showed that membrane binding is highly cooperative with an apparent Kd of 180 nM and Bmax of 230 nM. Taken together, these results demonstrate high-affinity GC-binding on the cell membrane of AtT-20 cells with characteristics distinct from intracellular binding.

Intracellular substrates for the primer-unblocking reaction by human immunodeficiency virus type 1 reverse transcriptase: detection and quantitation in extracts from quiescent- and activated-lymphocyte subpopulations

Treatment of human immunodeficiency virus type 1 (HIV-1)-infected patients with 3'-azido-3'-deoxythymidine (AZT) selects for mutant forms of viral reverse transcriptase (RT) with increased ability to remove chain-terminating nucleotides from blocked DNA chains. We tested various cell extracts for the presence of endogenous acceptor substrates for this reaction. Cell extracts incubated with HIV-1 RT and [(32)P]ddAMP-terminated DNA primer/template gave rise to (32)P-labeled adenosine 2',3'-dideoxyadenosine 5',5'''-P(1),P(4)-tetraphosphate (Ap(4)ddA), ddATP, Gp(4)ddA, and Ap(3)ddA, corresponding to the transfer of [(32)P]ddAMP to ATP, PP(i), GTP, and ADP, respectively. Incubation with [(32)P]AZT monophosphate (AZTMP)-terminated primer/template gave rise to the analogous (32)P-labeled AZT derivatives. Based on the rates of formation of the specific excision products, ATP and PP(i) levels were determined: ATP was present at 1.3 to 2.2 mM in H9 cells, macrophages, and unstimulated CD4(+) or CD8(+) T cells, while PP(i) was present at 7 to 15 microM. Under these conditions, the ATP-dependent reaction predominated, and excision by the AZT-resistant mutant RT was more efficient than wild type RT. Activated CD4(+) or CD8(+) T cells contained 1.4 to 2.7 mM ATP and 55 to 79 microM PP(i). These cellular PP(i) concentrations are lower than previously reported; nonetheless, the PP(i)-dependent reaction predominated in extracts from activated T cells, and excision by mutant and wild-type RT occurred with similar efficiency. While PP(i)-dependent excision may contribute to AZT resistance in vivo, it is likely that selection of AZT-resistant mutants occurs primarily in an environment where the ATP-dependent reaction predominates.

Bioenergetics of immune cells to assess rheumatic disease activity and efficacy of glucocorticoid treatment

OBJECTIVE

To investigate whether activity and glucocorticoid treatment of rheumatic diseases are reflected by selected parameters of cellular energy metabolism of peripheral blood mononuclear cells (PBMC).

METHODS

PBMC were obtained from 30 healthy volunteers, 28 patients (16 inactive; 12 active) with rheumatoid arthritis, systemic lupus erythematosus, vasculitis, or other autoimmune diseases, and five patients with infectious diseases. Patients with active rheumatic diseases were examined before and 4-5 days after starting, restarting, or increasing the dose of glucocorticoids. Cellular oxygen consumption (as a measure of ATP production), bioenergetic ability to be stimulated, and major ATP consuming processes were measured amperometrically with a Clark electrode.

RESULTS

A normal value for oxygen consumption of 3.84 (SEM 0.1) (all data in nmol O(2)/min/10(7) cells) independent of sex was found. In patients with inactive disease the respiration rate was slightly higher, but was significantly increased in active patients to 4.82 (SEM 0.33) (p<0.001). PBMC from active patients showed a significantly lower bioenergetic response to a mitogenic stimulus than controls (p<0.05). In stimulated cells from active patients there was a significant reduction in cation transport and protein synthesis. All parameters above were almost normalised within 4-5 days upon optimised treatment with glucocorticoids. For comparison, PBMC from patients with active infectious diseases also showed an increased respiration rate; their response to mitogenic stimulation was even higher.

CONCLUSIONS

This study shows for the first time that parameters describing the cellular function of PBMC in bioenergetic terms are suitable for (a) describing semiquantitatively the activity of a rheumatic disease and (b) assessing the therapeutic effect on the disease.

Effect of corticosteroids on viability and proliferation of the rainbow trout monocyte/macrophage cell line, RTS11

Cortisol at 1,000 and 100 ng/ml, and less consistently at 10 ng/ml, inhibited increases in cell number and 3H-thymidine incorporation by cultures of the rainbow trout (Oncorhynchus mykiss) monocyte/macrophage cell line, RTS11. Cell viability was not altered by cortisol, although a small decline in the capacity of cultures to reduce the redox dye, Alamar Blue was observed. In cortisol-treated cultures, more round and fewer spread cells were evident. Similar results were observed with dexamethasone but not cortisone. The glucocorticoid receptor antagonist, RU-486, prevented the effects of cortisol on RTS11 proliferation, and shape. In co-culture with the spleen stroma cell line (RTS34st) or in medium conditioned by RTS34st, the proliferation of RTS11 was enhanced. Treating RTS11/RTS34st co-cultures or RTS11 cultures in RTS34st conditioned medium with cortisol did not inhibit RTS11 proliferation. Overall these experiments suggest that proliferation of rainbow trout macrophages is regulated by cortisol, but the effect is modulated by the cellular micro-environment, possibly through the release of cytokines.

Hierarchies of ATP-consuming processes: direct compared with indirect measurements, and comparative aspects

The original aim of the present study was to deal with two problems that had emerged from a study on hierarchies of ATP-consuming processes in cells [Buttgereit and Brand (1995) Biochem. J. 312, 163-167]. Firstly, we wanted to find out whether the results of that study had been influenced by the method used for the determination of process activity and, secondly, we wondered whether and to what extent the structure of the hierarchy established for cell suspensions under energy-limiting conditions might depend on the type of cell or on the lifestyle, ecology and phylogenetic status of the species from which the cells were derived. We confined our study to the two most prominent ATP consumers of cells: protein synthesis and the Na(+)/K(+)-ATPase, measuring their activity directly by [3H]leucine incorporation and Rb(+)-flux respectively. We found large differences in the sensitivity of protein synthesis to energy limitation between hepatocytes from an anoxia-tolerant fish species and an anoxia-sensitive fish species (goldfish and rainbow trout respectively). On the other hand, Na(+)/K(+)-ATPase activity was hardly affected by energy limitation in the hepatocytes from both fish species. We also studied the response of a human hepatoma cell line, HepG2, to energy limitation and found both protein synthesis and Na(+)/K(+)-ATPase activity to be equally sensitive to energy limitation, but more sensitive than the Na(+)/K(+)-ATPase of the two fish species. A comparison of the indirect and direct methods for measuring protein synthesis revealed the rate of oxygen consumption to be functionally related to the concentration of cycloheximide, the inhibitor used. It was found that at 15 mM cycloheximide [three orders of magnitude higher than the concentration at which the incorporation of free amino acids (FAA) into protein is inhibited] total oxygen consumption was suppressed by 71-75%, whereas the measured rate of [3H]leucine incorporation into protein suggested that the cycloheximide-sensitive fraction should have amounted to not more than approx. 10% of the total oxygen consumption. On the other hand, the amount of oxygen consumption suppressed with the high concentration of cycloheximide corresponded almost exactly to the increase in oxygen consumption of cells incubated in an FAA-enriched medium compared with cells incubated in a standard, FAA-free medium. Our major conclusions are, firstly, that high concentrations of cycloheximide disrupt cellular metabolism, bringing to a standstill all those processes that can be stimulated by incubating starved cells in an FAA-enriched medium, secondly, that the attempt to estimate the metabolic cost of protein synthesis by inhibiting oxygen consumption with cycloheximide leads to spurious results, and, thirdly, that the structure of a 'hierarchy' of ATP-consumers may reflect the lifestyle and physiology of the species studied.