Unlocking CAR T cell potential: Inosine-induced stemness and enhanced potency

Adenosine (Ado) drives immune suppression in the tumor microenvironment. In this issue of Cancer Cell, Klysz et al. investigate Ado-mediated immunosuppression. Overexpression of Ado deaminase (ADA-OE), metabolizing Ado to inosine (INO), induces stemness and improves CAR T cell functionality. Likewise, exposure to INO enhances CAR T cells' function and induces stemness features.

L-arginine metabolism inhibits arthritis and inflammatory bone loss

OBJECTIVES

To investigate the effect of the L-arginine metabolism on arthritis and inflammation-mediated bone loss.

METHODS

L-arginine was applied to three arthritis models (collagen-induced arthritis, serum-induced arthritis and human TNF transgenic mice). Inflammation was assessed clinically and histologically, while bone changes were quantified by μCT and histomorphometry. In vitro, effects of L-arginine on osteoclast differentiation were analysed by RNA-seq and mass spectrometry (MS). Seahorse, Single Cell ENergetIc metabolism by profilIng Translation inHibition and transmission electron microscopy were used for detecting metabolic changes in osteoclasts. Moreover, arginine-associated metabolites were measured in the serum of rheumatoid arthritis (RA) and pre-RA patients.

RESULTS

L-arginine inhibited arthritis and bone loss in all three models and directly blocked TNFα-induced murine and human osteoclastogenesis. RNA-seq and MS analyses indicated that L-arginine switched glycolysis to oxidative phosphorylation in inflammatory osteoclasts leading to increased ATP production, purine metabolism and elevated inosine and hypoxanthine levels. Adenosine deaminase inhibitors blocking inosine and hypoxanthine production abolished the inhibition of L-arginine on osteoclastogenesis in vitro and in vivo. Altered arginine levels were also found in RA and pre-RA patients.

CONCLUSION

Our study demonstrated that L-arginine ameliorates arthritis and bone erosion through metabolic reprogramming and perturbation of purine metabolism in osteoclasts.

Xie Zhuo Tiao Zhi formula modulates intestinal microbiota and liver purine metabolism to suppress hepatic steatosis and pyroptosis in NAFLD therapy

BACKGROUND

Current evidence indicates a rising global prevalence of Non-Alcoholic Fatty Liver Disease (NAFLD), which is closely associated to conditions such as obesity, dyslipidemia, insulin resistance, and metabolic syndrome. The relationship between the gut microbiome and metabolites in NAFLD is gaining attention understanding the pathogenesis and progression of dysregulated lipid metabolism and inflammation. The Xie Zhuo Tiao Zhi (XZTZ) decoction has been employed in clinical practice for alleviating hyperlipidemia and symptoms related to metabolic disorders. However, the pharmacological mechanisms underlying the effects of XZTZ remain to be elucidated.

PURPOSE

The objective of this study was to examine the pharmacological mechanisms underlying the hypolipidemic and anti-inflammatory effects of XZTZ decoction in a mouse model of NAFLD, as well as the effects of supplementing exogenous metabolites on PO induced cell damage and lipid accumulation in cultured hepatocytes.

METHODS

A high-fat diet (HFD) mouse model was established to examine the effects of XZTZ through oral gavage. The general condition of mice and the protective effect of XZTZ on liver injury were evaluated using histological and biochemical methods. Hematoxylin and eosin staining (H&E) staining and oil red O staining were performed to assess inflammatory and lipid accumulation detection, and cytokine levels were quantitatively analyzed. Additionally, the study included full-length 16S rRNA sequencing, liver transcriptome analysis, and non-targeted metabolomics analysis to investigate the relationship among intestinal microbiome, liver metabolic function, and XZTZ decoction.

RESULTS

XZTZ had a significant impact on the microbial community structure in NAFLD mice. Notably, the abundance of Ileibacterium valens, which was significantly enriched by XZTZ, exhibited a negative correlation with liver injury biomarkers such as, alanine transaminase (ALT) and aspartate transaminase (AST) activity. Moreover, treatment with XZTZ led to a significant enrichment of the purine metabolism pathway in liver tissue metabolites, with inosine, a purine metabolite, showing a significant positive correlation with the abundance of I. valens. XZTZ and inosine also significantly enhanced fatty acid β-oxidation, which led to a reduction in the expression of pro-inflammatory cytokines and the inhibition of liver pyroptosis. These effects contributed to the mitigation of liver injury and hepatocyte damage, both in vivo and vitro. Furthermore, the utilization of HPLC fingerprints and UPLC-Q-TOF-MS elucidated the principal constituents within the XZTZ decoction, including naringin, neohesperidin, atractylenolide III, 23-o-Acetylalisol B, pachymic acid, and ursolic acid which are likely responsible for its therapeutic efficacy. Further investigations are imperative to fully uncover and validate the pharmacodynamic mechanisms underlying these observations.

CONCLUSION

The administration of XZTZ decoction demonstrates a protective effect on the livers of NAFLD mice by inhibiting lipid accumulation and reducing hepatocyte inflammatory damage. This protective effect is mediated by the upregulation of I.valens abundance in the intestine, highlighting the importance of the gut-liver axis. Furthermore, the presesnce of inosine, adenosine, and their derivatives are important in promoting the protective effects of XZTZ. Furthermore, the in vitro approaching, we provide hitherto undocumented evidence indicating that the inosine significantly improves lipid accumulation, inflammatory damage, and pyroptosis in AML12 cells incubated with free fatty acids.

8-Aminopurines in the Cardiovascular and Renal Systems and Beyond

Screening of compounds comprising 8-substituted guanine revealed that 8-aminoguanosine and 8-aminoguanine cause diuresis/natriuresis/glucosuria, yet decrease potassium excretion. Subsequent investigations demonstrated that 8-aminoguanosine's effects are mediated by its metabolite 8-aminoguanine. The mechanism by which 8-aminoguanine causes diuresis/natriuresis/glucosuria involves inhibition of PNPase (purine nucleoside phosphorylase), which increases renal interstitial inosine levels. Additional evidence suggests that inosine, via indirect or direct adenosine A2B receptor activation, increases renal medullary blood flow which enhances renal excretory function. Likely, 8-aminoguanine has pleiotropic actions that also alter renal excretory function. Indeed, the antikaliuretic effects of 8-aminoguanine are independent of PNPase inhibition. 8-Aminoguanine is an endogenous molecule; nitrosative stress leads to production of biomolecules containing 8-nitroguanine moieties. Degradation of these biomolecules releases 8-nitroguanosine and 8-nitro-2'-deoxyguanosine which are converted to 8-aminoguanine. Also, guanosine and guanine per se may contribute to 8-aminoguanine formation. 8-Aminoinosine, 8-aminohypoxanthine, and 8-aminoxanthine likewise induce diuresis/natriuresis/glucosuria, yet do not reduce potassium excretion. Thus, there are several pharmacologically active 8-aminopurines with nuanced effects on renal excretory function. Chronic treatment with 8-aminoguanine attenuates hypertension in deoxycorticosterone/salt rats, prevents strokes, and increases lifespan in Dahl salt-sensitive rats on a high salt diet and attenuates the metabolic syndrome in rats; 8-aminoguanosine retards progression of pulmonary hypertension in rats and anemia and organ damage in sickle cell mice. 8-Aminoguanine reverses age-associated lower urinary tract dysfunction and retinal degeneration. 8-Aminopurines represent a new class of agents (and potentially endogenous factors) that have beneficial effects on the cardiovascular system and kidneys and may turn back the clock in age-associated diseases.

Effects of different levels of inosine-5'-monophosphate (5'-IMP) supplementation on the growth performance and meat quality of finishing pigs (75 to 100 kg)

This study aimed to assess the effects of dietary supplementation of inosine-5'-monophosphate (5'-IMP) on energy efficiency, growth performance, carcass characteristics, meat quality, oxidative status, and biochemical profile of blood plasma in finishing pigs. Fifty-four crossbred castrated male pigs were distributed in a randomized block design consisting of nine blocks, with six treatments per block and one animal per treatment per block. Experimental diets were as follows: positive control diet (PC, 3300 kcal ME/kg), negative control diet (NC, 3200 kcal ME/kg), and four diets prepared by supplementing the NC diet with 0.050%, 0.100%, 0.150%, or 0.200% 5'-IMP. Based on regression analysis, supplementation with 0.129% 5'-IMP increased average daily weight gain (1.30 kg). Backfat thickness, pH45minutes and redness of m. Longissimus Lumborum (LL) increased linearly with 5'-IMP supplementation level. Drip loss and pH at 24 h post-slaughter had a quadratic response to 5'-IMP supplementation. It is concluded that 5'-IMP supplementation positively influenced growth performance, carcass characteristics and LL meat quality in finishing barrows.

A plastid nucleoside kinase is involved in inosine salvage and control of purine nucleotide biosynthesis

In nucleotide metabolism, nucleoside kinases recycle nucleosides into nucleotides-a process called nucleoside salvage. Nucleoside kinases for adenosine, uridine, and cytidine have been characterized from many organisms, but kinases for inosine and guanosine salvage are not yet known in eukaryotes and only a few such enzymes have been described from bacteria. Here we identified Arabidopsis thaliana PLASTID NUCLEOSIDE KINASE 1 (PNK1), an enzyme highly conserved in plants and green algae belonging to the Phosphofructokinase B family. We demonstrate that PNK1 from A. thaliana is located in plastids and catalyzes the phosphorylation of inosine, 5-aminoimidazole-4-carboxamide-1-β-d-ribose (AICA ribonucleoside), and uridine but not guanosine in vitro, and is involved in inosine salvage in vivo. PNK1 mutation leads to increased flux into purine nucleotide catabolism and, especially in the context of defective uridine degradation, to over-accumulation of uridine and UTP as well as growth depression. The data suggest that PNK1 is involved in feedback regulation of purine nucleotide biosynthesis and possibly also pyrimidine nucleotide biosynthesis. We additionally report that cold stress leads to accumulation of purine nucleotides, probably by inducing nucleotide biosynthesis, but that this adjustment of nucleotide homeostasis to environmental conditions is not controlled by PNK1.

Inosine, gut microbiota, and cancer immunometabolism

This article briefly reviews cancer immunity and the role of gut microbiota in carcinogenesis, followed by an understanding of mechanisms by which inosine is involved in cancer immunometabolism. The immune system plays a paradoxical role in cancer treatment. Antitumor immunity depends on the T-cell priming against tumor antigens, whereas inflammatory mediators trigger the protumor signaling in the tumor microenvironment. Studies link the microbiome with metabolism and immunity-two main factors implicated in carcinogenesis. Gut microbiota has been shown to affect both antitumor immunity and protumor immune signaling. There is mounting evidence that the human microbiome can play a role in the immunotherapeutic effects, both response and resistance. Inosine-5'-monophosphate dehydrogenase (IMPDH) is a highly conservative enzyme widely expressed in mammals. Cell signaling pathways use molecular inosine, a crucial secondary metabolite in purine metabolism and a molecular messenger. Recent research has identified inosine as a critical regulator of immune checkpoint inhibition (ICI) therapeutic response in various tumor types. Some bacterial species were found to produce inosine or its metabolite hypoxanthine and induce T-helper 1 differentiation and effector functions via the inosine-A2AR-cAMP-PKA pathway upon ICI therapy. Also, inosine acts as a substitute carbon source for T-cell metabolism in glucose-restricted environments, i.e., the tumor microenvironment, assisting T-cell proliferation and differentiation while enhancing sensitivity to ICI, reinforcing the notion that inosine metabolism might contribute to antitumor immunity. Also, inosine is a potent agonist of the adenosine receptor, A2AR, and A2AR signaling can affect T-cell responses and antitumor immunity, making the inosine-A2AR pathway blockage a candidate for cancer treatment. Further research is required to investigate inosine as a cancer immunometabolism therapy.

Apoptotic brown adipocytes enhance energy expenditure via extracellular inosine

Brown adipose tissue (BAT) dissipates energy1,2 and promotes cardiometabolic health3. Loss of BAT during obesity and ageing is a principal hurdle for BAT-centred obesity therapies, but not much is known about BAT apoptosis. Here, untargeted metabolomics demonstrated that apoptotic brown adipocytes release a specific pattern of metabolites with purine metabolites being highly enriched. This apoptotic secretome enhances expression of the thermogenic programme in healthy adipocytes. This effect is mediated by the purine inosine that stimulates energy expenditure in brown adipocytes by the cyclic adenosine monophosphate-protein kinase A signalling pathway. Treatment of mice with inosine increased BAT-dependent energy expenditure and induced 'browning' of white adipose tissue. Mechanistically, the equilibrative nucleoside transporter 1 (ENT1, SLC29A1) regulates inosine levels in BAT: ENT1-deficiency increases extracellular inosine levels and consequently enhances thermogenic adipocyte differentiation. In mice, pharmacological inhibition of ENT1 as well as global and adipose-specific ablation enhanced BAT activity and counteracted diet-induced obesity, respectively. In human brown adipocytes, knockdown or blockade of ENT1 increased extracellular inosine, which enhanced thermogenic capacity. Conversely, high ENT1 levels correlated with lower expression of the thermogenic marker UCP1 in human adipose tissues. Finally, the Ile216Thr loss of function mutation in human ENT1 was associated with significantly lower body mass index and 59% lower odds of obesity for individuals carrying the Thr variant. Our data identify inosine as a metabolite released during apoptosis with a 'replace me' signalling function that regulates thermogenic fat and counteracts obesity.

Succinate and inosine coordinate innate immune response to bacterial infection

Macrophages restrict bacterial infection partly by stimulating phagocytosis and partly by stimulating release of cytokines and complement components. Here, we treat macrophages with LPS and a bacterial pathogen, and demonstrate that expression of cytokine IL-1β and bacterial phagocytosis increase to a transient peak 8 to 12 h post-treatment, while expression of complement component 3 (C3) continues to rise for 24 h post-treatment. Metabolomic analysis suggests a correlation between the cellular concentrations of succinate and IL-1β and of inosine and C3. This may involve a regulatory feedback mechanism, whereby succinate stimulates and inosine inhibits HIF-1α through their competitive interactions with prolyl hydroxylase. Furthermore, increased level of inosine in LPS-stimulated macrophages is linked to accumulation of adenosine monophosphate and that exogenous inosine improves the survival of bacterial pathogen-infected mice and tilapia. The implications of these data suggests potential therapeutic tools to prevent, manage or treat bacterial infections.

Inosine induces acute hyperuricaemia in rhesus monkey (Macaca mulatta) as a potential disease animal model

CONTEXT

The uric acid metabolism pathway is more similar in primates and humans than in rodents. However, there are no reports of using primates to establish animal models of hyperuricaemia (HUA).

OBJECTIVES

To establish an animal model highly related to HUA in humans.

MATERIALS AND METHODS

Inosine (75, 100 and 200 mg/kg) was intraperitoneally administered to adult male rhesus monkeys (n = 5/group). Blood samples were collected over 8 h, and serum uric acid (SUA) level was determined using commercial assay kits. XO and PNP expression in the liver and URAT1, OAT4 and ABCG2 expression in the kidneys were examined by qPCR and Western blotting to assess the effects of inosine on purine and uric acid metabolism. The validity of the acute HUA model was assessed using ulodesine, allopurinol and febuxostat.

RESULTS

Inosine (200 mg/kg) effectively increased the SUA level in rhesus monkeys from 51.77 ± 14.48 at 0 h to 178.32 ± 14.47 μmol/L within 30 min and to peak levels (201.41 ± 42.73 μmol/L) at 1 h. PNP mRNA level was increased, whereas XO mRNA and protein levels in the liver were decreased by the inosine group compared with those in the control group. No changes in mRNA and protein levels of the renal uric acid transporter were observed. Ulodesine, allopurinol and febuxostat eliminated the inosine-induced elevation in SUA in tested monkeys.

CONCLUSIONS

An acute HUA animal model with high reproducibility was induced; it can be applied to evaluate new anti-HUA drugs in vivo and explore the disease pathogenesis.

Physiology and effects of nucleosides in mice lacking all four adenosine receptors

Adenosine is a constituent of many molecules of life; increased free extracellular adenosine indicates cell damage or metabolic stress. The importance of adenosine signaling in basal physiology, as opposed to adaptive responses to danger/damage situations, is unclear. We generated mice lacking all four adenosine receptors (ARs), Adora1^−/−;Adora2a^−/−;Adora2b^−/−;Adora3^−/− (quad knockout [QKO]), to enable investigation of the AR dependence of physiologic processes, focusing on body temperature. The QKO mice demonstrate that ARs are not required for growth, metabolism, breeding, and body temperature regulation (diurnal variation, response to stress, and torpor). However, the mice showed decreased survival starting at about 15 weeks of age. While adenosine agonists cause profound hypothermia via each AR, adenosine did not cause hypothermia (or bradycardia or hypotension) in QKO mice, indicating that AR-independent signals do not contribute to adenosine-induced hypothermia. The hypothermia elicited by adenosine kinase inhibition (with A134974), inosine, or uridine also required ARs, as each was abolished in the QKO mice. The proposed mechanism for uridine-induced hypothermia is inhibition of adenosine transport by uridine, increasing local extracellular adenosine levels. In contrast, adenosine 5′-monophosphate (AMP)–induced hypothermia was attenuated in QKO mice, demonstrating roles for both AR-dependent and AR-independent mechanisms in this process. The physiology of the QKO mice appears to be the sum of the individual knockout mice, without clear evidence for synergy, indicating that the actions of the four ARs are generally complementary. The phenotype of the QKO mice suggests that, while extracellular adenosine is a signal of stress, damage, and/or danger, it is less important for baseline regulation of body temperature.

A study of mice lacking all four adenosine receptors shows that while they mediate effects of uridine, inosine and adenosine, these receptors are dispensable for growth, metabolism, breeding, and body temperature regulation. This suggests that extracellular adenosine is a damage or danger signal, rather than a major regulator of baseline physiology.

Elevated extracellular adenosine generally indicates metabolic stress or cell damage and regulates many aspects of physiology. We studied “QKO” mice lacking all four adenosine receptors. Young QKO mice do not appear obviously ill, but do show decreased survival later in life. QKO mice demonstrate that adenosine receptors are not required for growth, metabolism, breeding, and body temperature regulation. QKO mice are missing the pharmacologic effects of adenosine on body temperature, heart rate, and blood pressure. Therefore, all of these effects are mediated by the four adenosine receptors. We also determined that the hypothermic effects of a pharmacologic adenosine kinase inhibitor (A134974), uridine, or inosine each requires adenosine receptors. The uridine-induced hypothermia is likely due to its inhibition of adenosine uptake into cells. QKO mouse physiology appears to be the sum of the individual knockout mice, without evidence for synergy, indicating that the actions of the four adenosine receptors are generally complementary.

Amitriptyline Attenuates Ca2+ Responses Induced by Glutoxim and Molixan in Macrophages

Using Fura-2AM microfluorimetry, we have shown for the first time that sigma-1 receptor agonist, tricyclic antidepressant amitriptyline, significantly inhibits glutoxim- and molixan-induced Ca2+-responses in rat peritoneal macrophages. The results suggest possible involvement of sigma-1 receptors in the signaling cascade induced by glutoxim or molixan and leading to intracellular Ca2+ concentration increase in macrophages.

Guanine and inosine nucleotides/nucleosides suppress murine T cell activation

Damaged tissues and cells release intracellular purine nucleotides, which serve as intercellular signaling factors. We previously showed that exogenously added adenine nucleotide (250 μM ATP) suppressed the activation of murine splenic T lymphocytes. Here, we examined the effects of other purine nucleotides/nucleosides on mouse T cell activation. First, we found that pretreatment of mouse spleen T cells with 250 μM GTP, GDP, GMP, guanosine, ITP, IDP, IMP or inosine significantly reduced the release of stimulus-inducible cytokine IL-2. This suppression of IL-2 release was not caused by induction of cell death. Further studies with GTP, ITP, guanosine and inosine showed that pretreatment with these nucleotides/nucleosides also suppressed release of IL-6. However, these nucleotides/nucleosides did not suppress stimulus-induced phosphorylation of ERK1/2, suggesting that the suppression of the release of inflammatory cytokines does not involve inhibition of ERK1/2 signaling. In contrast to ATP pretreatment at the same concentration, guanine or inosine nucleotides/nucleosides did not attenuate the expression of CD25. Our findings indicate that exogenous guanine or inosine nucleotides/nucleosides can suppress inflammatory cytokine release from T cells, and may be promising candidates for use as supplementary agents in the treatment of T cell-mediated immune diseases.

Sigma-1 receptor antagonist haloperidol attenuates Ca2+ responses induced by glutoxim and molixan in macrophages

Using Fura-2AM microfluorimetry, we have shown for the first time that sigma-1 receptor antagonist, antipsychotic haloperidol, significantly inhibits glutoxim- and molixan-induced Ca2+-response in peritoneal macrophages. These results indicate possible involvement of sigma-1 receptors in the signal cascade induced by glutoxim or molixan and leading to intracellular Ca2+ concentration increase in macrophages.

Bioactivity of 2'-deoxyinosine-incorporated aptamer AS1411

Aptamers can be chemically modified to enhance nuclease resistance and increase target affinity. In this study, we performed chemical modification of 2'-deoxyinosine in AS1411, an anti-proliferative G-rich oligodeoxynucleotide aptamer, which binds selectively to the nucleolin protein. Its function was augmented when 2'-deoxyinosine was incorporated at positions 12, 13, 15, and 24 of AS1411, respectively. In addition, double incorporation of 2'-deoxyinosine at positions 12 and 24 (FAN-1224dI), 13 and 24 (FAN-1324dI), and 15 and 24 (FAN-1524dI) promoted G-quartet formation, as well as inhibition of DNA replication and tumor cell growth, and induced S-phase cell cycle arrest. In further animal experiments, FAN-1224dI, FAN-1324dI and FAN-1524dI resulted in enhanced treatment effects than AS1411 alone. These results suggested that the position and number of modification substituents in AS1411 are critical parameters to improve the diagnostic and therapeutic function of the aptamer. Structural investigations of the FAN-1524dI/nucleolin complex structure, using molecular dynamics simulation, revealed the critical interactions involving nucleolin and 2'-dI incorporated AS1411 compared with AS1411 alone. These findings augment understanding of the role of 2'-deoxyinosine moieties in interactive binding processes.

Inosine Improves Neurogenic Detrusor Overactivity following Spinal Cord Injury

Neurogenic detrusor overactivity and the associated loss of bladder control are among the most challenging complications of spinal cord injury (SCI). Anticholinergic agents are the mainstay for medical treatment of detrusor overactivity. However, their use is limited by significant side effects such that a search for new treatments is warranted. Inosine is a naturally occurring purine nucleoside with neuroprotective, neurotrophic and antioxidant effects that is known to improve motor function in preclinical models of SCI. However, its effect on lower urinary tract function has not been determined. The objectives of this study were to determine the effect of systemic administration of inosine on voiding function following SCI and to delineate potential mechanisms of action. Sprague−Dawley rats underwent complete spinal cord transection, or cord compression by application of an aneurysm clip at T8 for 30 sec. Inosine (225 mg/kg) or vehicle was administered daily via intraperitoneal injection either immediately after injury or after a delay of 8 wk. At the end of treatment, voiding behavior was assessed by cystometry. Levels of synaptophysin (SYP), neurofilament 200 (NF200) and TRPV1 in bladder tissues were measured by immunofluorescence imaging. Inosine administration decreased overactivity in both SCI models, with a significant decrease in the frequency of spontaneous non−voiding contractions during filling, compared to vehicle−treated SCI rats (p<0.05), including under conditions of delayed treatment. Immunofluorescence staining demonstrated increased levels of the pan-neuronal marker SYP and the Adelta fiber marker NF200, but decreased staining for the C-fiber marker, TRPV1 in bladder tissues from inosine-treated rats compared to those from vehicle-treated animals, including after delayed treatment. These findings demonstrate that inosine prevents the development of detrusor overactivity and attenuates existing overactivity following SCI, and may achieve its effects through modulation of sensory neurotransmission.

Modulation versus rescue of antimetabolite toxicity by salvage metabolites administered by continuous infusion

A system has been developed for the long-term continuous intravenous infusion of chemotherapeutic agents into unrestrained mice which allows new approaches to the toxicological and chemotherapeutic evaluation of antimetabolites. In mice, the concurrent infusion of thymidine and a source of preformed purine reversed both the toxicity and antitumor activity of MTX comparable to what was previously observed in cell culture. The infusion of thymidine alone, however, also blocked the toxicity of MTX without interfering with antitumor activity. A comparison of leucovorin rescue versus the utilization of thymidine plus preformed purine indicated that these salvage metabolites were as effective as leucovorin in reducing the toxicity of high-dose MTX while retaining antitumor activity.

P2Y₂ receptor activation decreases blood pressure via intermediate conductance potassium channels and connexin 37

AIMS

Nucleotides are important paracrine regulators of vascular tone. We previously demonstrated that activation of P2Y₂ receptors causes an acute, NO-independent decrease in blood pressure, indicating this signalling pathway requires an endothelial-derived hyperpolarization (EDH) response. To define the mechanisms by which activation of P2Y₂ receptors initiates EDH and vasodilation, we studied intermediate-conductance (KCa3.1, expressed in endothelial cells) and big-conductance potassium channels (KCa1.1, expressed in smooth muscle cells) as well as components of the myoendothelial gap junction, connexins 37 and 40 (Cx37, Cx40), all hypothesized to be part of the EDH response.

METHODS

We compared the effects of a P2Y₂/₄ receptor agonist in wild-type (WT) mice and in mice lacking KCa3.1, KCa1.1, Cx37 or Cx40 under anaesthesia, while monitoring intra-arterial blood pressure and heart rate.

RESULTS

Acute activation of P2Y₂/₄ receptors (0.01-3 mg kg(-1) body weight i.v.) caused a biphasic blood pressure response characterized by a dose-dependent and rapid decrease in blood pressure in WT (maximal response % of baseline at 3 mg kg(-1) : -38 ± 1%) followed by a consecutive increase in blood pressure (+44 ± 11%). The maximal responses in KCa3.1(-/-) and Cx37(-/-) were impaired (-13 ± 5, +17 ± 7 and -27 ± 1, +13 ± 3% respectively), whereas the maximal blood pressure decrease in response to acetylcholine at 3 μg kg(-1) was not significantly different (WT: -53 ± 3%; KCa3.1(-/-) : -52 ± 3; Cx37(-/-) : -53 ± 3%). KCa1.1(-/-) and Cx40(-/-) showed an identical biphasic response to P2Y2/4 receptor activation compared to WT.

CONCLUSIONS

The data suggest that the P2Y2/4 receptor activation elicits blood pressure responses via distinct mechanisms involving KCa3.1 and Cx37.

Inhibition of platelet activation and thrombus formation by adenosine and inosine: studies on their relative contribution and molecular modeling

Background

The inhibitory effect of adenosine on platelet aggregation is abrogated after the addition of adenosine-deaminase. Inosine is a naturally occurring nucleoside degraded from adenosine.

Objectives

The mechanisms of antiplatelet action of adenosine and inosine in vitro and in vivo, and their differential biological effects by molecular modeling were investigated.

Results

Adenosine (0.5, 1 and 2 mmol/L) inhibited phosphatidylserine exposure from 52±4% in the control group to 44±4 (p<0.05), 29±2 (p<0.01) and 20±3% (p<0.001). P-selectin expression in the presence of adenosine 0.5, 1 and 2 mmol/L was inhibited from 32±4 to 27±2 (p<0.05), 14±3 (p<0.01) and 9±3% (p<0.001), respectively. At the concentrations tested, only inosine to 4 mmol/L had effect on platelet P-selectin expression (p<0.05). Adenosine and inosine inhibited platelet aggregation and ATP release stimulated by ADP and collagen. Adenosine and inosine reduced collagen-induced platelet adhesion and aggregate formation under flow. At the same concentrations adenosine inhibited platelet aggregation, decreased the levels of sCD40L and increased intraplatelet cAMP. In addition, SQ22536 (an adenylate cyclase inhibitor) and ZM241385 (a potent adenosine receptor A_2A antagonist) attenuated the effect of adenosine on platelet aggregation induced by ADP and intraplatelet level of cAMP. Adenosine and inosine significantly inhibited thrombosis formation in vivo (62±2% occlusion at 60 min [n = 6, p<0.01] and 72±1.9% occlusion at 60 min, [n = 6, p<0.05], respectively) compared with the control (98±2% occlusion at 60 min, n = 6). A_2A is the adenosine receptor present in platelets; it is known that inosine is not an A_2A ligand. Docking of adenosine and inosine inside A_2A showed that the main difference is the formation by adenosine of an additional hydrogen bond between the NH₂ of the adenine group and the residues Asn253 in H6 and Glu169 in EL2 of the A_2A receptor.

Conclusion

Therefore, adenosine and inosine may represent novel agents lowering the risk of arterial thrombosis.

Inosine-arginine salt as a promising agent for in vitro activation of waterborne fish-pathogenic myxozoan actinospores

Mucus-derived nucleosides serve as key host cues for myxozoan actinospore fish host recognition, but to date their use for experimental actinospore activation in the laboratory or application in disease prevention has not progressed very far. One obstacle has been the low solubility of pure inosine and guanosine. To overcome this, we used inosine-arginine salt (ino-arg), which incorporates both high activation properties and high solubility. We tested its efficacy both in microassays directly observing reactions of actinospores of 2 distantly related myxozoan species, Myxobolus cerebralis and M. pseudodispar in comparison to inosine, as well as its actinospore-inactivation properties by premature polar capsule discharge in an infection experiment. Ino-arg was considerably more effective in eliciting polar capsule discharge and sporoplasm emission at much lower concentrations than pure inosine and, in contrast to the latter, remained dissolved in aqueous solution. Ino-arg exposure of M. pseudodispar actinospores resulted in polar capsule discharge and sporoplasm emission before host contact and subsequently in a lower infection rate in roach Rutilus rutilus.

The antidepressant-like effect of inosine in the FST is associated with both adenosine A1 and A 2A receptors

Inosine is an endogenous purine nucleoside, which is formed during the breakdown of adenosine. The adenosinergic system was already described as capable of modulating mood in preclinical models; we now explored the effects of inosine in two predictive models of depression: the forced swim test (FST) and tail suspension test (TST). Mice treated with inosine displayed higher anti-immobility in the FST (5 and 50 mg/kg, intraperitoneal route (i.p.)) and in the TST (1 and 10 mg/kg, i.p.) when compared to vehicle-treated groups. These antidepressant-like effects started 30 min and lasted for 2 h after intraperitoneal administration of inosine and were not accompanied by any changes in the ambulatory activity in the open-field test. Both adenosine A1 and A2A receptor antagonists prevented the antidepressant-like effect of inosine in the FST. In addition, the administration of an adenosine deaminase inhibitor (1 and 10 mg/kg, i.p.) also caused an antidepressant-like effect in the FST. These results indicate that inosine possesses an antidepressant-like effect in the FST and TST probably through the activation of adenosine A1 and A2A receptors, further reinforcing the potential of targeting the purinergic system to the management of mood disorders.

[Pharmacological activity of runihol and S-adenosyl-L-methionine in rats with experimental liver damage by reserve antituberculosis drugs]

The hepatoprotective action of runihol and S-adenosyl-L-methionine (ademethionine) has been studied in a group of 47 white outbred male rats with model liver injury induced by reserve antituberculosis drugs (PAS, prothionamide, cycloserine). The ability of test drugs to correct structural and functional liver disorders is established. Both runihol and ademethionine favored decrease in the signs of structural and functional liver disorders induced by reserve antituberculosis drugs, Showing mixed type of action, the test drugs promoted recovery of the liver parenchyma and reduced manifestations of hepatocyte dystrophy to the same extent, without manifestations of necrobiotic processes and a mononuclear infiltration.

[Some inhibitors of purine nucleoside phosphorylase]

Purine nucleoside phosphorylase (PNP) catalyzes reversible phosphorolysis of purine deoxy- and ribonucleosides with formation (d)Rib-1-P and corresponding bases. PNP plays a leading role in the cell metabolism of nucleosides and nucleotides, as well as in maintaining the immune status of an organism. The major aim of the majority of studies on the PNP is the detection of highly effective inhibitors of this enzyme, derivatives ofpurine nucleosides used in medicine as immunosuppressors, which are essential for creating selective T-cell immunodeficiency in a human body for organ and tissue transplantation. The present work is devoted to the study of the effects of some synthetic derivatives of purine nucleosides on activity of highly purified PNP from rabbit spleen and also from human healthy and tumor tissues of lung and kidneys. Purine nucleoside analogues modified at various positions of both the heterocyclic base and carbohydrate residues have been investigated. Several compounds, including 8-mercapto-acyclovir, 8-bromo-9-(3,4-hydroxy-butyl)guanine, which demonstrated potent PNP inhibition, could be offered for subsequent study as immunosuppressors during organ and tissue transplantation.

Anti-inflammatory effects of purine nucleosides, adenosine and inosine, in a mouse model of pleurisy: evidence for the role of adenosine A2 receptors

Adenosine and its metabolite, inosine, have been described as molecules that participate in regulation of inflammatory response. The aim of this study was to investigate the effect of adenosine and inosine in a mouse model of carrageenan-induced pleurisy as well as the participation of adenosine receptors in this response. Injection of carrageenan into the pleural cavity induced an acute inflammatory response characterized by leukocyte migration, pleural exudation, and increased release of interleukin-1β and tumor necrosis factor-α in pleural exudates. The treatment with adenosine (0.3-100 mg/kg, i.p.) and inosine (0.1-300 mg/kg, i.p.) 30 min before carrageenan injection reduced significantly all these parameters analyzed. Our results also demonstrated that A(2A) and A(2B) receptors seem to mediate the adenosine and inosine effects observed, since pretreatment with selective antagonists of adenosine A(2A) (ZM241385) and A(2B) (alloxazine) receptors, reverted the inhibitory effects of adenosine and inosine in pleural inflammation. The involvement of A(2) receptors was reinforced with adenosine receptor agonist CGS21680 treatment, since its anti-inflammatory effects were reversed completely and partially with ZM241385 and alloxazine injection, respectively. Moreover, the combined treatment with subeffective dose of adenosine (0.3 mg/kg) and inosine (1.0 mg/kg) induced a synergistic anti-inflammatory effect. Thus, based on these findings, we propose that inosine contributes with adenosine to exert anti-inflammatory effects in pleural inflammation, reinforcing the notion that endogenous nucleosides play an important role in controlling inflammatory diseases. This effect is likely mediated by the activation of adenosine A(2) subtype receptors and inhibition of production or release of pro-inflammatory cytokines.

[Effect of Korargin on reactivity of isolation aorta of adult and old irradiated rats]

Introduction to the diet of adult (7-8 months) and old (24-26 months) male rats for 30 days after a single R-irradiation at a dose of 5 Gy of preparation "Korargin" (whose active ingredients are L-arginine, contributing to the prevention of endothelial dysfunction, and inosine) in old irradiated rats significantly increased the relaxation of isolated segments of thoracic aorta by the action of acetylcholine, sodium nitroprusside and insulin. In adults irradiated animals this effect was not observed. Vasoconstriction response of isolated segments of thoracic aorta to norepinephrine was decreased in isolated segments of thoracic aorta by adults and old irradiated rats compared with controls, and application of korargin had no significant effect. Thus, in old irradiated rats, in contrast to adult irradiated animals, the use of korargin increased of vascular sensitiveness to act of endothelial-dependent and endothelial-nondependent vazodilatators, helped to preserve of endothelial function and increase the capacity of vazodilatator potential.

[The involvement of actin cytoskeleton in glutoxim and molixan effect on intracellular Ca(2+)-concentration in macrophages]

Glutoxim and molixan belong to new generation of disulfide-containing drugs with immunomodulatory, hepatoprotective and hemopoetic effect on cells. Using Fura-2AM microfluorimetry, two structurally distinct actin filament disrupters, latrunculin B and cytochalasin D, and calyculin A, which causes actin filaments condensation under plasmalemma, we have shown the involvement of actin cytoskeleton in the intracellular Ca(2+)-concentration increase induced by glutoxim or molixan in rat peritoneal macrophages. Morphological data obtained with the use of rhodamine-phalloidine have demonstrated that glutoxim and molixan cause the actin cytoskeleton reorganization in rat peritoneal macrophages.

Improvement of mitochondrial energy and oxidative balance during intestinal differentiation

Mitochondria vary in their number and function, but how these variations are associated with intestinal cell differentiation remains elusive. The object of this study was to investigate the underlying mechanisms of inosine-mediated intestinal cell maturation, analysing the effects of this nutrient on metabolic functionality, mitochondrial biogenesis and mitochondrial function in human colonic cells. The role of oxidative stress in the control of intestinal cell growth was also explored. We report the novel finding that inosine-mediated differentiation improves aerobic metabolism through an increase in mitochondrial bioenergetics and biogenesis in colonic cells, which probably confers them greater resistance to cytotoxic oxidative stress.

Effects of L-alanine and inosine germinants on the elasticity of Bacillus anthracis spores

The surface of dormant Bacillus anthracis spores consists of a multilayer of protein coats and a thick peptidoglycan layer that allow the cells to resist chemical and environmental insults. During germination, the spore coat is degraded, making the spore susceptible to chemical inactivation by antisporal agents as well as to mechanical inactivation by high-pressure or mechanical abrasion processes. While chemical changes during germination, especially the release of the germination marker, dipicolinic acid (DPA), have been extensively studied, there is as yet no investigation of the corresponding changes in the mechanical properties of the spore. In this work, we use atomic force microscopy (AFM) to characterize the mechanical properties of the surface of Bacillus anthracis spores during germination. The Hertz model of continuum mechanics of contact was used to evaluate the Young's moduli of the spores before and after germination by applying the model to load-indentation curves. The highest modulus was observed for dormant spores, with average elasticity values of 197 +/- 81 MPa. The elasticity decreased significantly after incubation of the spores with the germinants L-alanine or inosine (47.5 +/- 41.7 and 35.4 +/- 15.8 MPa, respectively). Exposure of B. anthracis spores to a mixture of both germinants resulted in a synergistic effect with even lower elasticity, with a Young's modulus of 23.5 +/- 14.8 MPa. The elasticity of the vegetative B. anthracis cells was nearly 15 times lower than that of the dormant spores (12.4 +/- 6.3 MPa vs 197.0 +/- 80.5 MPa, respectively). Indeed from a mechanical strength point of view, the germinated spores were closer to the vegetative cells than to the dormant spores. Further, the decrease in the elasticity of the cells was accompanied by increasing AFM tip indentation depths on the cell surfaces. Indentation depths of up to 246.2 nm were observed for vegetative B. anthracis compared to 20.5 nm for the dormant spores. These results provide quantitative information on how the mechanical properties of the cell wall change during germination, which may explain how spores become susceptible to inactivation processes based on mechanical forces during germination and outgrowth. The study of spore elasticity may be a valuable tool in the design of improved antisporal treatments.

Role of the gerP operon in germination and outgrowth of Bacillus anthracis spores

Germination of Bacillus anthracis spores occurs when nutrients such as amino acids or purine nucleosides stimulate specific germinant receptors located in the spore inner membrane. The gerP(ABCDEF) operon has been suggested to play a role in facilitating the interaction between germinants and their receptors in spores of Bacillus subtilis and Bacillus cereus. B. anthracis mutants containing deletions in each of the six genes belonging to the orthologue of the gerP(ABCDEF) operon, or deletion of the entire operon, were tested for their ability to germinate. Deletion of the entire gerP operon resulted in a significant delay in germination in response to nutrient germinants. These spores eventually germinated to levels equivalent to wild-type, suggesting that an additional entry point for nutrient germinants may exist. Deletions of each individual gene resulted in a similar phenotype, with the exception of DeltagerPF, which showed no obvious defect. The removal of two additional gerPF-like orthologues was necessary to achieve the germination defect observed for the other mutants. Upon physical removal of the spore coat, the mutant lacking the full gerP operon no longer exhibited a germination defect, suggesting that the GerP proteins play a role in spore coat permeability. Additionally, each of the gerP mutants exhibited a severe defect in calcium-dipicolinic acid (Ca-DPA)-dependent germination, suggesting a role for the GerP proteins in this process. Collectively, these data implicate all GerP proteins in the early stages of spore germination.

The treatment of multiple sclerosis with inosine

OBJECTIVE

The objective of this study is to evaluate the safety and tolerability of inosine in patients with relapsing-remitting multiple sclerosis (RRMS). The secondary objectives are to assess the effects of inosine administration on serum urate (UA) levels, the progression of neurologic disability, the cumulative number of new, active lesions on magnetic resonance imaging (MRI), and changes in serum levels for markers of inflammation.

DESIGN

Oral administration of inosine was used to raise serum levels of the natural peroxynitrite scavenger UA in 16 patients with RRMS during a 1-year randomized, double-blind trial.

OUTCOME MEASURES

The endpoints studied were relapse rate, disability assessed by the Kurtzke Expanded Disability Status Scale (EDSS), MRI, and analysis of serum levels of nitrotyrosine, and oxidative and pro-inflammatory makers.

RESULTS

Increased serum UA levels correlated with a significant decrease in the number of gadolinium-enhanced lesions and improved EDSS. A number of MRI intensity-based parameters were altered by inosine treatment, in certain cases correlating with changes in serum UA levels. In a patient with low serum UA and high lesion activity, raising UA levels by inosine treatment decreased serum nitrotyrosine while increasing the ratio of Th2 to Th1 cytokines in circulating cells. The only side-effect correlated with inosine treatment was kidney stone formation in 4/16 subjects.

CONCLUSIONS

These data suggest that the use of inosine to raise serum UA levels may have benefits for at least some MS patients. The effect of this treatment is likely to be a consequence of inactivation of peroxynitrite-dependent free radicals. Close monitoring of serum UA levels as well as other measures are required to avoid the potential development of kidney stones.

In vitro pharmacology of inosine, with special reference to possible interactions with capsaicin-sensitive mechanisms and inflammatory mediators

The in vitro pharmacology of inosine (Ino), a putative anti-inflammatory compound, has been investigated in smooth muscle preparations, with emphasis on its possible interaction with known inflammatory mediators, as well as capsaicin, an inducer of "neurogenic inflammation". The highest concentration of Ino routinely studied was 1 mM, since 10 mM nonspecifically inhibited many types of smooth muscle motor responses. In the guinea pig isolated ileum or trachea, Ino (1 mM) failed to influence the excitatory effect of capsaicin. The nitric oxide (NO)-mediated relaxant effect of capsaicin in the human colonic circular muscle was not influenced by Ino. Ino only weakly reduced the contractile effect of histamine on the guinea pig ileum. Substance P-mediated nonadrenergic, noncholinergic (NANC) contractions evoked by electrical stimulation in the guinea pig ileum were inhibited by half by Ino (1 mM). Ino showed no or only a weak inhibitory effect on NANC relaxation of the rat ileum. Arachidonic acid- or leukotriene D(4)-induced contractions of the guinea pig ileum were only moderately inhibited by Ino. Collectively, these results indicate that Ino (up to 1 mM) shows no major antagonist activity at histamine H(1) receptors, leukotriene CysLT(1) receptors, the transient receptor potential channel TRPV1 or tachykinin NK(1) or NK(2) receptors, or cyclooxygenase-inhibitory activity. Therefore, its anti-inflammatory activity is probably not associated with these mechanisms. The in vitro methods used in this study are capable of detecting a wide range of biological effects and hence may be recommended as a screening procedure for potential drugs or natural products.

The novel inosine analogue, INO-2002, protects against diabetes development in multiple low-dose streptozotocin and non-obese diabetic mouse models of type I diabetes

Endogenous purines including inosine have been shown to exert immunomodulatory and anti-inflammatory effects in a variety of disease models. The dosage of inosine required for protection is very high because of the rapid metabolism of inosine in vivo. The aim of this study was to determine whether a metabolic-resistant purine analogue, INO-2002, exerts anti-inflammatory effects in two animal models of type I diabetes. Type I diabetes was induced chemically with streptozotocin or genetically using the non-obese diabetic (NOD) female mouse model. Mice were treated with INO-2002 or inosine as required at 30, 100, or 200 mg/kg per day, while blood glucose and diabetes incidence were monitored. The effect of INO-2002 on the pancreatic cytokine profile was also determined. INO-2002 reduced both the hyperglycaemia and incidence of diabetes in both streptozotocin-induced and spontaneous diabetes in NOD mice. INO-2002 proved to be more effective in protecting against diabetes than the naturally occurring purine, inosine, when administered at the same dose. INO-2002 treatment decreased pancreatic levels of interleukin (IL)-12 and tumour necrosis factor-alpha, while increasing levels of IL-4 and IL-10. INO-2002 also reduced pancreatic levels of the chemokine MIP-1 alpha. The inosine analogue, INO-2002, was protected more effectively than the naturally occurring purine, inosine, against development of diabetes in two separate animal models. INO-2002 exerts protective effects by changing the pancreatic cytokine expression from a destructive Th1 to a protective Th2 profile. The use of analogues of inosine such as INO-2002 should be considered as a potential preventative therapy in individuals susceptible to developing type I diabetes.

[The gerA operon is required for spore germination in Bacillus thuringiensis]

Spore germination of Bacillus could be triggered by germinants like L-alanine which is thought to bind to and stimulate specific receptors. The GerA receptor responds to L-alanine in Bacillus subtilis. A homologous gerA operon of B. subtilis was isolated from Bacillus thuringiensis subsp. kurstaki. RT-PCR showed that the transcription of the gerA operon was switched on 3 hours after the initiation of sporulation and this operon was cotranscribed. Disruption of the gerA operon led to blockage of the L-alanine-initiated germination pathway and showed a delayed inosine-induced germination response. The germination rate of the gerA complementary strain spore deriving from introducing gerA operon into the disruption mutant was even faster than that of the wild type strain spore. This is caused by overdose GerA receptors which could enhance the sensibility of complementary spore to L-alanine. The overdose GerA receptors came from introducing multicopy plasmid- pKSV7 (about five copies) which could increase the amount of GerA receptors. After treatment of D-cycloserine which could inactivate alanine racemase irreversibly, L-alanine-induced spore could germinate faster than untreated spore. The combination of 0.1 mmol/L D-cycloserine and 1 mmol/L L-alanine could trigger spore germination induced by L-alanine effectively.

[Microcirculatory disturbance in the course of acute pancreatitis]

Although as many studies are sacrificed to acute pancreatitis (AP), the pathogenesis of the disease remains undiscovered. The microcirculatory disturbances during AP as a cause of necrotic changes in the parenchyma of the gland, described first time by Panum in 1886, have become again a very attractive theory. In the last decades, several studies were done to prove that microcirculatory impairment plays a crucial role in pathogenesis of severe AP. It had been proved that many mediators play important roles in this process including nitric oxide and endothelin balance. Vasoconstriction and vasodilatation named "vascular game" caused by cytokine accumulation and lower oxygenation of the tissue gives very interesting basis for theories about creating pancreatic necrosis. The severity of the course of AP also determinates damage of the microcirculation of the lungs, the liver and the bowels which leads to SIRS, MODS and MOF. The new experimental dates seems to be very promising and can became a basis for developing a new strategy of treatment in the most severe cases of AP. In this article we present up-to-date information about these theories and concepts.

Simultaneous application of two neurotrophic factors after spinal cord injury

We have studied the application of voltage gradients to injured spinal cord which enhanced regeneration of axons and reduced their retrograde degeneration after injury. This led to an implanted electronic device producing electrical fields sufficient to induce regeneration in both ascending and descending tracts of white matter (called oscillating field stimulation [OFS]), which has been associated with behavioral recovery in animal models of spinal cord injury (SCI). OFS has also proven to benefit neurologically complete spinal cord injured dogs and humans in clinical trials. These studies, however, have failed to confirm benefit if applied after the sub-acute period of SCI. Here we report on combining OFS with the application of a non-toxic neurotrophic factor, inosine, using a behavioral model for "chronic" SCI, the cutaneous trunci muscle (CTM) reflex in adult guinea pigs. Inosine was delivered subcutaneously in guinea pigs for 28 days using implantable "osmotic pumps"--alone or in combination with OFS. In all animals, experimental and control treatments were withheld for three months after a right lateral hemisection of the thoracic spinal cord. Both inosine and the combination therapy produced a statistically significant recovery of CTM receptive fields silenced permanently by spinal cord hemisection in controls--though the combination therapy enhanced the time of the appearance of recovered regions of skin. Retransection of the cord in three recovered animals eliminated the CTM recovery confirming changes in neural connections were restricted to the cord and not due to changes in cutaneous peripheral innervation. Morphometry of anterogradely labeled white matter revealed a statistically enhanced regeneration of ascending and descending projections in animals treated with the combination "therapy" compared to inosine alone. These data suggest that combining neurotrophic factors of differing modes of action likely enhance the outcome from "chronic" SCI.

Germination of Bacillus cereus spores adhered to stainless steel

Adhered spores of Bacillus cereus represent a significant part of the surface-derived contamination in processing equipment used in the dairy industry. As germinated spores lose their resistance capacities instantaneously, efficient germination prior to a cleaning in place treatment could aid to the disinfecting effect of such a treatment. Therefore, spores of B. cereus ATCC 14579 and that of the environmental isolate B. cereus CMCC 3328 were assessed for their germination behaviour when adhered to a stainless steel surface. A mixture of l-alanine and inosine initiated germination of adhered spores efficiently, resulting in 3.2 decimal logarithms of germination. Notably, implementation of a germination-inducing step prior to a representative cleaning in place procedure reduced the number of survivors with over 3 decimal log units, while an alkali treatment alone, as part of the cleaning in place procedure, did not show any effect on B. cereus spore viability. These results show that implementation of a germination step enhances the disinfection effect of currently used cleaning in place procedures.

Uric acid heralds ischemic tissue injury to mobilize endothelial progenitor cells

Understanding the nature of endogenous mechanisms for mobilization of stem/progenitor cells is predicated on the identification of injury-induced substances that are released from a damaged organ and capable of producing a distant effect. Although different substances that mobilize endothelial progenitor cells (EPCs) have been proposed, their potential to signal injury and afford postischemic renoprotection and repair remains obscure. Uric acid (UA) is consistently overproduced by ischemic tissues and has been shown to exert immunomodulatory functions. It was hypothesized that UA and/or its precursors might serve as injury signals that are capable of mobilizing EPCs in acute renal ischemia. Indeed, FVB/NJ mice that were subjected to acute renal ischemia showed a transient surge in UA level in the peripheral blood. Single-dose treatment with UA, as well as acute hyperuricemia induced by the inhibition of uricase, caused a robust mobilization of EPCs, whereas administration of adenosine or inosine seemed to lack this effect. Moreover, pretreatment of mice with a single dose of UA afforded significant renoprotection against ischemic injury. In animals with chronic hyperuricemia (induced by continuous 2-wk treatment with a uricase inhibitor oxonic acid), EPC mobilization was blunted and renoprotective effects were absent. In conclusion, acute elevation of UA acts as "physiologic," fast-acting endogenous mediator of EPC mobilization and renoprotection, consistent with its novel function in pharmacologic preconditioning. Both of these actions are lacking in mice with chronic hyperuricemia. In summary, a transient surge in UA concentration may serve as a universal herald of tissue injury to accelerate the recruitment of EPCs.

Immunomodulatory effect of the purine nucleoside inosine following spinal cord contusion injury in rat

STUDY DESIGN

In vivo study using a moderate spinal cord contusion injury (SCI) model in adult rat.

OBJECTIVE

To assess the immunomodulatory effects of the purine nucleoside inosine on macrophage/microglia activation at and near the lesion site and in white matter areas remote from the injury epicenter.

SETTING

Department of Cell and Developmental Biology, SUNY Upstate Medical University, Syracuse, NY, USA.

METHODS

Animals (N=56) were injured using a moderate SCI at T9-T10 spinal level and were divided into three groups, depending on treatment paradigm. Rats received either intraperitoneal or subcutaneous injections of inosine (N=28) or vehicle (N=28). Spinal cord tissue was processed for ED-1 immunoreactivity and the volume fraction of ED-1(+) profiles was calculated using the Cavalieri method and unbiased stereology.

RESULTS

The volume fraction of ED-1(+) profiles within gray and lateral white matter regions at and around the lesion site was significantly reduced only following a twice daily-6 week treatment course, compared with vehicle controls, and white matter areas remote from the lesion were unaffected by all inosine treatment paradigms.

CONCLUSIONS

Continued subcutaneous delivery of inosine, beginning 15-min post-SCI and persisting throughout the survival period of 6 weeks exerted immunomodulatory effects at and around the lesion site.

Thymidine phosphorylase is noncompetitively inhibited by 5'-O-trityl-inosine (KIN59) and related compounds

We found that 5'-O-trityl-inosine (KIN59) inhibits recombinant bacterial (E. coli) and human thymidine phosphorylase (TPase) with an IC50 of 44 microM and 67 microM, respectively. In contrast to previously described TPase inhibitors, KIN59 does not compete with thymidine (dThd) at the pyrimidine nucleoside-binding site or with inorganic phosphate (Pi) at the phosphate-binding site of the enzyme. These findings are strongly suggestive for the presence of an allosteric binding site at the enzyme. TPase is identical to the angiogenic protein platelet-derived endothelial cell growth factor (PD-ECGF). As such, PD-ECGF stimulates angiogenesis in the chick chorioallantoic membrane (CAM) assay. This angiogenic response was completely inhibited by KIN59. Inosine did not inhibit the enzyme or the angiogenic effect of TPase, confirming that the 5'-O-trityl group in KIN59 is essential for the observed effect. Our observations indicate that allosteric sites in TPase may regulate its biological activity.

[Guanosine and inosine as natural geneprotectors for mice blood cells exposed to X-rays]

The radioprotective effects of guanosine and of inosine on bone marrow cells of mice exposed to acute X-rays (1.5 Gy) were studied by using the micronuclear test. The guanosine and inosine (riboxine) decrease the frequency of micronucleated polychromatic erythrocytes and significantly recover erythropoiesis. Also, radioprotective effects of the guanosine and of the inosine on the irradiated leucocytes of mice were tested by the alkaline comet assay. Was shown that purine ribonucleosides diminish quantity of DNA damage and activates repair processes in leucocytes under irradiation of blood and animals. The reactive oxygen species induced by ionizing radiation perform essential role in DNA damaging. Using a sensitive method of enhanced chemiluminescence in a peroxidase-luminol-p-iodophenol system for quantitative measurement of hydrogen peroxide and coumarin-3-carboxylic acid for quantitative measurement of hydroxyl radicals we have shown that guanosine and inosine essentially decrease the yield of hydrogen peroxide and hydroxyl radicals in X-ray-irradiated water. The results obtained indicate that radioprotective properties of guanosine and inosine (riboxine) in the blood cells are operative at the genome level.

Effects of inosine on neuronal apoptosis and the expression of cytochrome C mRNA following hypoxic-ischemic brain damage in neonatal rats

OBJECTIVE

It has been reported that neuronal apoptosis plays a critical role in pathology of hypoxic-ischemic encephalopathy (HIE). Cytochrome C (CytC) is an important apoptotic protease activating factor. Inosine might have a neuroprotective effect against cerebral ischemia reperfusion injury by inhibiting the neuronal apoptosis and the expression of CytC mRNA in adult rats. This study examined the effects of inosine on neuronal apoptosis and CytC mRNA expression following hypoxic-ischemic brain damage (HIBD) in order to investigate the neuroprotectivity of inosine against cerebral ischemia injury in neonatal rats and the possible mechanism.

METHODS

A total of 140 healthy 7-day-old Sprague-Dawley rat pups were randomly assigned into Control (n=40), HIBD (n=50) and Inosine treatment groups (n=50). HIBD rat models were established by ligating the left common carotid artery, followed by 8% O2 hypoxia exposure for 2 hrs in the HIBD and Inosine treatment groups. The Control group was not subjected to hypoxia-ischemia (HI). The Inosine treatment and the HIBD groups were randomly divided into 5 sub-groups sacrificed at 6 and 12 hrs, and 1, 3 and 7 days post- HI (n=10 each). The Control group rats were sacrificed at the corresponding time points (n=8 each). Inosine was administered to the Inosine treatment group by intraperitoneal injection immediately after HIBD at the dosage of 100 mg/kg twice daily for 7 days. TUNEL staining and in situ hybridization method was used to detect neuronal apoptosis and CytC mRNA expression respectively.

RESULTS

Few apoptotic cells and CytC mRNA positive cells were found in brain tissues of the Control group. In the HIBD group, the number of apoptotic cells and the CytC mRNA expression in the cortical and hippocampal gyrum CA1 areas increased 6 hrs after HI, peaking at 1 day after HI and then decreased gradually. Until the 7th day, the number of apoptotic cells and the CytC mRNA expression in the cortical and hippocampal gyrum CA1 areas in the HIBD group remained significantly higher than in the Control group. Inosine treatment decreased the apoptotic cells and the CytC mRNA expression in both areas from 6 hrs to 7 days after HI compared with the HIBD group. The linear correlation analysis demonstrated that the number of apoptotic cells was positively correlated to the CytC mRNA expression in neonatal rats with HIBD (r=0.88, P < 0.01) .

CONCLUSIONS

Inosine can reduce the number of apoptotic cells and down-regulate the expression of CytC mRNA following HIBD in neonatal rats. The decreased number of apoptotic cells was positively correlated to the decreased CytC mRNA expression after inosine treatment, suggesting that inosine offered neuroprotectivity against HIBD possibly through inhibiting the CytC mRNA expression and resulting in a decrease of cell apoptosis.

Markedly enhancing lipase-catalyzed synthesis of nucleoside drugs’ ester by using a mixture system containing organic solvents and ionic liquid

Eightfold higher yields and three times faster reaction rates were achieved by means of using a mixture solvent system composed of 90% acetone and 10% [BMIM]BF4 in the lipase-catalyzed regioselective synthesis of polymerizable ester of nucleoside drugs.

Inosine released after hypoxia activates hepatic glucose liberation through A3 adenosine receptors

Inosine, an endogenous nucleoside, has recently been shown to exert potent effects on the immune, neural, and cardiovascular systems. This work addresses modulation of intermediary metabolism by inosine through adenosine receptors (ARs) in isolated rat hepatocytes. We conducted an in silico search in the GenBank and complete genomic sequence databases for additional adenosine/inosine receptors and for a feasible physiological role of inosine in homeostasis. Inosine stimulated glycogenolysis (approximately 40%, EC50 4.2 x 10(-9) M), gluconeogenesis (approximately 40%, EC50 7.8 x 10(-9) M), and ureagenesis (approximately 130%, EC50 7.0 x 10(-8) M) compared with basal values; these effects were blunted by the selective A3 AR antagonist 9-chloro-2-(2-furanyl)-5-[(phenylacetyl)amino][1,2,4]-triazolo[1,5-c]quinazoline (MRS 1220) but not by selective A1, A2A, and A2B AR antagonists. In addition, MRS 1220 antagonized inosine-induced transient increase (40%) in cytosolic Ca2+ and enhanced (90%) glycogen phosphorylase activity. Inosine-induced Ca2+ mobilization was desensitized by adenosine; in a reciprocal manner, inosine desensitized adenosine action. Inosine decreased the cAMP pool in hepatocytes when A1, A2A, and A2B AR were blocked by a mixture of selective antagonists. Inosine-promoted metabolic changes were unrelated to cAMP decrease but were Ca2+ dependent because they were absent in hepatocytes incubated in EGTA- or BAPTA-AM-supplemented Ca2+-free medium. After in silico analysis, no additional cognate adenosine/inosine receptors were found in human, mouse, and rat. In both perfused rat liver and isolated hepatocytes, hypoxia/reoxygenation produced an increase in inosine, adenosine, and glucose release; these actions were quantitatively greater in perfused rat liver than in isolated cells. Moreover, all of these effects were impaired by the antagonist MRS 1220. On the basis of results obtained, known higher extracellular inosine levels under ischemic conditions, and inosine's higher sensitivity for stimulating hepatic gluconeogenesis, it is suggested that, after tissular ischemia, inosine contributes to the maintenance of homeostasis by releasing glucose from the liver through stimulation of A3 ARs.

[Effects of inosine injection in expression of myosin heavy chain in intrafusal and extrafusal myofibers in soleus muscle of tail-suspended rats]

AIM

To study the effects of inosine on myosin heavy chain (MHC) activity in rats soleus muscle after tail-suspension.

METHODS

Weightlessness was simulated by tail-suspension of rats. Using immunohistochemistry technique, changes of expression of MHC in intrafusal and extrafusal fibers in soleus muscle were detected.

RESULTS

Expression of fast MHC in intrafusal and extrafusal fibers in soleus muscle increased after 14 d of simulated weightlessness, whereas in tail-suspended rats given inosine, the expression of fast MHC was not detected.

CONCLUSION

Inosine could counteract the changes in expression of MHC in intrafusal and extrafusal fibers of rats soleus under simulated weightless situation.

Characterization of germination receptors of Bacillus cereus ATCC 14579

Specific amino acids, purine ribonucleosides, or a combination of the two is required for efficient germination of endospores of Bacillus cereus ATCC 14579. A survey including 20 different amino acids showed that l-alanine, l-cysteine, l-threonine, and l-glutamine are capable of initiating the germination of endospores of B. cereus ATCC 14579. In addition, the purine ribonucleosides inosine and adenosine can trigger germination of the spores. Advanced annotation of the B. cereus ATCC 14579 genome revealed the presence of seven putative germination (ger) operons, termed gerG, gerI, gerK, gerL, gerQ, gerR, and gerS. To determine the role of the encoded putative receptors in nutrient-induced germination, disruption mutants were constructed by the insertion of pMUTIN4 into each of the seven operons. Four of the seven mutants were affected in the germination response to amino acids or purine ribonucleosides, whereas no phenotype could be attributed to the mutants with disrupted gerK, gerL, and gerS loci. The strain with a disrupted gerR operon was severely hampered in the ability to germinate: germination occurred in response to l-glutamine but not in the presence of any of the other amino acids tested. The gerG mutant showed significantly reduced l-glutamine-induced germination, which points to a role of this receptor in the l-glutamine germination signaling pathway. gerR, gerI, and gerQ mutants showed reduced germination rates in the presence of inosine, suggesting a role for these operons in ribonucleoside signaling. Efficient germination by the combination of l-glutamine and inosine was shown to involve the gerG and gerI operons, since the germination of mutants lacking either one of these receptors was significantly reduced. Germination triggered by the combination of l-phenylalanine and inosine was lost in the gerI mutant, indicating that both molecules are effective at the GerI receptor.

The nucleotide derivatives inosine and inosinic acid inhibit intestinal absorption of mizoribine in rats

Inosine is absorbed via a N1 transporter that is selective for purine nucleosides. It is conceivable that inosine and inosinic acid might affect the intestinal absorption of mizoribine, an imidazole nucleoside that inhibits the de novo production pathway of guanine ribonucleotide. An in situ loop experiment was performed using four intestinal loop segments prepared by ligation: segment 1, about 6 to 9 cm from the end of the pylorus; segment 2, about 10 to 13 cm; segment 3, about 14 to 17 cm; and segment 4, about 18 to 21 cm. Mizoribine (0.1 mg/ml) or mizoribine+inosine (1 or 10 mg/ml) were infused into each loop. The absorption rate in the most proximal segment of intestinal loop was the highest. In the presence of inosine, this rate decreased significantly. Urinary recovery rates of mizoribine were significantly decreased by pretreatment with inosine or inosinic acid. The Cmax in the group given mizoribine+inosinic acid was significantly lower than that in the group given mizoribine alone. These results strongly indicate that (I) the N1 transporter in the intestine might act to absorb mizoribine; and (II) inosine and inosinic acid might competitively inhibit the absorption of mizoribine via the N1 transporter.

Development of stealth liposome formulation of 2'-deoxyinosine as 5-fluorouracil modulator: in vitro and in vivo study

PURPOSE

The aims of this study were to develop a stealth, pegylated liposomal formulation of 2'-deoxyinosine (d-Ino), a 5-fluorouracil (5-FU) modulator, to evaluate its efficacy in vitro and in tumor-bearing mice, and to study its pharmacokinetics in rats.

METHOD

After designing a pegylated liposome encapsulating d-Ino (L-d-Ino), we evaluated its efficacy as 5-FU modulator in vitro. Antiproliferative assays, thymidylate synthase (TS) inhibition, and apoptosis studies were carried out to check whether an optimization of 5-FU action was achieved on the 5-FU-resistant SW620 cell line. Animal pharmacokinetic and ex vivo studies were next performed to confirm that L-d-Ino displayed a slower plasma elimination pattern than free d-Ino. Finally, effects on tumor growth of L-d-Ino + 5-FU combination was evaluated in xenografted mice.

RESULTS

We developed a stable, sterile, and homogenous 100-nm population of pegylated liposomes encapsulating 30% of d-Ino. Liposomal d-Ino exhibited a strong potential as 5-FU modulator in vitro by enhancing TS inhibition and subsequent apoptosis induction, while displaying a better pharmacokinetic profile in animals, with a near seven times clearance reduction as compared with the free form. When used in tumor-bearing mice in combination with 5-FU, our results showed next that the association led to 70% of tumor reduction with a doubling median survival time as compared with untreated animals, whereas 5-FU alone was ineffective.

CONCLUSION

Our data show that liposomal d-Ino, through an optimized pharmacokinetic profile, displays a potent effect as fluoropyrimidines modulator, both in vitro and in xenografted mice. Besides, we showed here that it is possible to reverse a resistant phenotype to 5-FU, a major drug extensively described in clinical oncology.

Functional characterization and haplotype analysis of polymorphisms in the human equilibrative nucleoside transporter, ENT2

The equilibrative nucleoside transporter 2 (ENT2; SLC29A2) is a bidirectional transporter that is involved in the disposition of naturally occurring nucleosides as well as a variety of anticancer and antiviral nucleoside analogs. The goal of the current study was to evaluate the function of genetic variants in ENT2 in cellular assays and to determine the haplotype structure of the coding and flanking intronic region of the gene. As part of a large study focused on genetic variation in membrane transporters (Leabman et al., 2003), DNA samples from ethnically diverse populations (100 African-Americans, 100 European-Americans, 30 Asians, 10 Mexicans, and 7 Pacific Islanders) were screened for variants in membrane transporters, including SLC29A2. Fourteen polymorphic sites in SLC29A2 were found, including 11 in the coding region. Five protein-altering variants were identified: three nonsynonymous variants, and two deletions. Each of the protein-altering variants was found at a very low frequency, occurring only once in the sample population. The nonsynonymous variants and the deletions were constructed via site-directed mutagenesis and were subsequently characterized in Xenopus laevis oocytes. All variants were able to take up inosine with the exception of ENT2-Delta845-846, which resulted in a frameshift mutation that prematurely truncated the protein. ENT2 showed very infrequent variation compared with most other transporter proteins studied, and it was found that five haplotypes were sufficient to describe the entire sample set. The low overall genetic diversity in SLC29A2 makes it unlikely that variation in the coding region contributes significantly to clinically observed differences in drug response.