S-adenosylmethionine protects post-ischemic mitochondrial injury in rat liver

Treatment with S-adenosylmethionine ameliorates irinotecan-induced intestinal barrier dysfunction and intestinal microbial disorder in mice

This study aimed to investigate the protective effects of S-adenosylmethionine (SAM) on irinotecan-induced intestinal barrier dysfunction and microbial ecological dysregulation in both mice and human colon cell line Caco-2, which is widely used for studying intestinal epithelial barrier function. Specifically, this study utilized Caco-2 monolayers incubated with 7-ethyl-10-hydroxycamptothecin (SN-38) as well as an irinotecan-induced diarrhea model in mice. Our study found that SAM pretreatment significantly reduced body weight loss and diarrhea induced by irinotecan in mice. Furthermore, SAM inhibited the increase of intestinal permeability in irinotecan-treated mice and ameliorated the decrease of Zonula occludens-1(ZO-1), Occludin, and Claudin-1 expression. Additionally, irinotecan treatment increased the relative abundance of Proteobacteria compared to the control group, an effect that was reversed by SAM administration. In Caco-2 monolayers, SAM reduced the expression of reactive oxygen species (ROS) and ameliorated the decrease in transepithelial electrical resistance (TER) and increase in fluorescein isothiocyanate-dextran 4000 Da (FD-4) flux caused by SN-38. Moreover, SAM attenuated changes in the localization and distribution of ZO-1and Occludin in Caco-2 monolayers induced by SN-38 and protected barrier function by inhibiting activation of the p38 MAPK/p65 NF-κB/MLCK/MLC signaling pathway. These findings provide preliminary evidence for the potential use of SAM in treating diarrhea caused by irinotecan.

Novel potential targets for prevention of arterial restenosis: insights from the pre-clinical research

Restenosis is the pathophysiological process occurring in 10-15% of patients submitted to revascularization procedures of coronary, carotid and peripheral arteries. It can be considered as an excessive healing reaction of the vascular wall subjected to arterial/venous bypass graft interposition, endarterectomy or angioplasty. The advent of bare metal stents, drug-eluting stents and of the more recent drug-eluting balloons, have significantly reduced, but not eliminated, the incidence of restenosis, which remains a clinically relevant problem. Biomedical research in pre-clinical animal models of (re)stenosis, despite its limitations, has contributed enormously to the identification of processes involved in restenosis progression, going well beyond the initial dogma of a primarily proliferative disease. Although the main molecular and cellular mechanisms underlying restenosis have been well described, new signalling molecules and cell types controlling the progress of restenosis are continuously being discovered. In particular, microRNAs and vascular progenitor cells have recently been shown to play a key role in this pathophysiological process. In addition, the advanced highly sensitive high-throughput analyses of molecular alterations at the transcriptome, proteome and metabolome levels occurring in injured vessels in animal models of disease and in human specimens serve as a basis to identify novel potential therapeutic targets for restenosis. Molecular analyses are also contributing to the identification of reliable circulating biomarkers predictive of post-interventional restenosis in patients, which could be potentially helpful in the establishment of an early diagnosis and therapy. The present review summarizes the most recent and promising therapeutic strategies identified in experimental models of (re)stenosis and potentially translatable to patients subjected to revascularization procedures.

Measurement of the S-adenosyl methionine (SAMe) content in a range of commercial veterinary SAMe supplements

OBJECTIVES

To measure the percentage of the stated amount of S-adenosyl methionine present in a range of commercially available S-adenosyl methionine supplements for veterinary use.

METHOD

Sixty-four samples of products containing S-adenosyl methionine marketed to support liver function were obtained from five manufacturers via three commercial wholesalers. The amount of S-adenosyl methionine in each product was measured using high-pressure liquid chromatography.

RESULTS

There were greater than threefold variation in the percentage of measured S-adenosyl methionine compared to the stated amount on the packaging which was significantly (P < 0 · 001) related to the product group being measured.

CLINICAL SIGNIFICANCE

Differences in received dose of S-adenosyl methionine between different products were marked and this could have a profound influence on studies that evaluate any variation in absorption of S-adenosyl methionine between different product formulations, the effectiveness of S-adenosyl methionine-based products in clinical cases or when translating the results of studies that have used a specific S-adenosyl methionine product to those produced by a different manufacturer.

Impaired expression of caveolin-1 contributes to hepatic ischemia and reperfusion injury

Caveolae are membrane structures enriched in glycosphingolipids and cholesterol, and caveolin-1 (Cav-1) has been recognized to be pivotal in ischemic tolerance. Sphingosine-1-phosphate (S1P), one of the sphingolipid metabolites, is well known for its anti-apoptotic properties, counteracting ischemia and reperfusion (IR) injury. Here, we investigated the cytoprotective mechanism of Cav-1 against IR injury. Male C57BL/6 mice underwent 70% hepatic ischemia for 60 min, followed by reperfusion. Mice were pretreated with methyl-beta-cyclodextrin (MβCD, 10, 25 and 50mg/kg, i.p.), a caveolae disruptor, or saline 48 and 24h before ischemia. Serum and liver tissues were collected at the end of ischemia, at 0, 1, 4 and 24h of reperfusion. Decreases in the expression of Cav-1 protein and in the number of caveolae of the liver ultrastructure were observed during IR, which were augmented by pretreatment with MβCD. MβCD also augmented the IR-induced increases in serum alanine aminotransferase and tumor necrosis factor-α levels. IR decreased the levels of sphingosine kinase 2 (SK2) and S1P receptor 2 (S1P2) mRNA expressions, while MβCD also augmented these decreases. Moreover, IR resulted in increases of mitochondrial cytochrome c release, caspase 3, 8 activities and Bax/Bcl-xL ratio, and MβCD augmented all of these apoptotic parameters. MβCD also increased p38 MAPK and JNK phosphorylation, but did not affect ERK and PI3K/Akt. Our findings demonstrate that downregulation of Cav-1 mediates IR-induced liver damage by inhibiting SK2/S1P2 signaling and enhancing the apoptotic pathway.

Effect of S-adenosylmethionine on neointimal formation after balloon injury in obese diabetic rats

AIMS

The association between hyperhomocysteinaemia and cardiovascular disease has been attributed to low levels of S-adenosylmethionine (SAM), a metabolic intermediate of homocysteine. However, the role of SAM in the development of restenosis has not been explored. Therefore, we investigated the effects of SAM on neointimal formation after balloon injury in obese diabetic rats and cultured cells.

METHODS AND RESULTS

Otsuka Long-Evans Tokushima fatty rats were divided into the following three groups: control (normal saline); SAM15; and SAM30 (15 and 30 mg/kg per day, respectively; n = 10 per group). SAM was administered orally from 1 week before carotid injury to 2 weeks thereafter. SAM treatment for 3 weeks caused a significant dose-dependent reduction in the intima-to-media ratio. SAM treatment significantly reduced the proliferation of vascular smooth muscle cells (VSMCs) and induced more apoptosis than was observed in the control group. This effect was accompanied by reduced circulating levels of high-sensitivity C-reactive protein and monocyte chemoattractant protein-1, reduced urine 8-hydroxy-2'-deoxyguanosine (8-OHdG), and increased adiponectin. Intima-to-media ratio correlated significantly with the levels of inflammatory markers, adiponectin, and 8-OHdG. In vitro experiments demonstrated that VSMC proliferation and migration and the adhesion of monocytes decreased in response to SAM. SAM treatment also reduced tumour necrosis factor-α-induced reactive oxygen species and tunicamycin-induced GRP78 expression in VSMCs.

CONCLUSION

These findings suggest that SAM exerts protective effects against restenosis after balloon injury in a rat model of type 2 diabetes by reducing the proliferation and inducing the apoptosis of VSMCs, modifying the inflammatory processes and reducing oxidative and endoplasmic reticulum stresses.

Hypotaurine is an Energy-Saving Hepatoprotective Compound against Ischemia-Reperfusion Injury of the Rat Liver

Metabolome analyses assisted by capillary electrophoresis-mass spectrometry (CE-MS) have allowed us to systematically grasp changes in small molecular metabolites under disease conditions. We applied CE-MS to mine out biomarkers in hepatic ischemia-reperfusion. Rat livers were exposed to ischemia by clamping of the portal inlet followed by reperfusion. Metabolomic profiling revealed that l contents of taurine in liver and plasma were significantly increased. Of interest is an elevation of hypotaurine, collectively suggesting significance of hypotaurine/taurine in post-ischemic responses. Considering the anti-oxidative capacity of hypotaurine, we examined if supplementation of the compound or its precursor amino acids could affect hepatocellular viability and contents of taurine in liver and plasma. Administration of hypotaurine, N-acetylcysteine or methionine upon reperfusion comparablly attenuated the post-ischemic hepatocellular injury but with different metabolomic profiling among groups: rats treated with methionine or N-acetylcysteine but not those treated with hypotaurine, exhibited significant elevation of hepatic lactate generation without notable recovery of the energy charge. Furthermore, the group treated with hypotaurine exhibited elevation of the plasma taurine, suggesting that the exogenously administered compound was utilized as an antioxidant. These results suggest that taurine serves as a surrogate marker for ischemia-reperfusion indicating effectiveness of hypotaurine as an energy-saving hepatoprotective amino acid.

Reactive oxygen species mediate liver injury through parenchymal nuclear factor-kappaB inactivation in prolonged ischemia/reperfusion

Nuclear factor (NF)-kappaB participates in ischemia/reperfusion (I/R) hepatic signaling, stimulating both protective mechanisms and the generation of inflammatory cytokines. After analyzing NF-kappaB activation during increasing times of ischemia in murine I/R, we observed that the nuclear translocation of p65 paralleled Src and IkappaB tyrosine phosphorylation, which peaked after 60 minutes of ischemia. After extended ischemic periods (90 to 120 minutes) however, nuclear p65 levels were inversely correlated with the progressive induction of oxidative stress. Despite this profile of NF-kappaB activation, inflammatory genes, such as tumor necrosis factor (TNF) and interleukin (IL)-1beta, predominantly induced by Kupffer cells, increased throughout time during ischemia (30 to 120 minutes), whereas protective NF-kappaB-dependent genes, such as manganese superoxide dismutase (Mn-SOD), expressed in parenchymal cells, decreased. Consistent with this behavior, gadolinium chloride pretreatment abolished TNF/IL-1beta up-regulation during ischemia without affecting Mn-SOD levels. Interestingly, specific glutathione (GSH) up-regulation in hepatocytes by S-adenosylmethionine increased Mn-SOD expression and protected against I/R-mediated liver injury despite TNF/IL-1beta induction. Similar protection was achieved by administration of the SOD mimetic MnTBAP. In contrast, indiscriminate hepatic GSH depletion by buthionine-sulfoximine before I/R potentiated oxidative stress and decreased both nuclear p65 and Mn-SOD expression levels, increasing TNF/IL-1beta up-regulation and I/R-induced liver damage. Thus, the divergent role of NF-kappaB activation in selective liver cell populations underlies the dichotomy of NF-kappaB in hepatic I/R injury, illustrating the relevance of specifically maintaining NF-kappaB activation in parenchymal cells.

Hydrogen sulfide triggers late-phase preconditioning in postischemic small intestine by an NO- and p38 MAPK-dependent mechanism

Hydrogen sulfide (H(2)S) is one of three endogenous gases, along with carbon monoxide (CO) and nitric oxide (NO), that exert a variety of important vascular actions in vivo. Although it has been demonstrated that CO or NO can trigger the development of a preconditioned phenotype in postischemic tissues, it is unclear whether H(2)S may also induce protection in organs subsequently exposed to ischemia-reperfusion (I/R). In light of these observations, we postulated that preconditioning with the exogenous H(2)S donor sodium hydrosulfide (NaHS-PC) would inhibit leukocyte rolling (LR) and adhesion (LA) induced by I/R. We used intravital microscopic techniques to demonstrate that NaHS-PC 24 h, but not 1 h, before I/R causes postcapillary venules to shift to an anti-inflammatory phenotype in wild-type (WT) mice such that these vessels fail to support LR and LA during reperfusion. The protective effect of NaHS-PC on LR was largely abolished by coincident pharmacological inhibition of NO synthase (NOS) in WT animals and was absent in endothelial NOS-deficient (eNOS(-/-)) mice. A similar pattern of response was noted in WT mice treated concomitantly with NaHS plus p38 mitogen-activated protein kinase (MAPK) inhibitors (SB 203580 or SK-86002). Whereas the reduction in LA induced by antecedent NaHS was attenuated by pharmacological inhibition of NOS or p38 MAPK in WT mice, the antiadhesive effect of NaHS was still evident in eNOS(-/-) mice. Thus NaHS-PC prevents LR and LA by triggering the activation of an eNOS- and p38 MAPK-dependent mechanism. However, the role of eNOS in the antiadhesive effect of NaHS-PC was less prominent than its effect to reduce LR.

Oxidative inactivation of key mitochondrial proteins leads to dysfunction and injury in hepatic ischemia reperfusion

BACKGROUND & AIMS

Ischemia-reperfusion (I/R) is a major mechanism of liver injury following hepatic surgery or transplantation. Despite numerous reports on the role of oxidative/nitrosative stress and mitochondrial dysfunction in hepatic I/R injury, the proteins that are oxidatively modified during I/R damage are poorly characterized. This study was aimed at investigating the oxidatively modified proteins underlying the mechanism for mitochondrial dysfunction in hepatic I/R injury. We also studied the effects of a superoxide dismutase mimetic/peroxynitrite scavenger metalloporphyrin (MnTMPyP) on oxidatively modified proteins and their functions.

METHODS

The oxidized and/or S-nitrosylated mitochondrial proteins from I/R-injured mouse livers with or without MnTMPyP pretreatment were labeled with biotin-N-maleimide, purified with streptavidin-agarose, and resolved by 2-dimensional gel electrophoresis. The identities of the oxidatively modified proteins were determined using mass spectrometric analysis. Liver histopathology, serum transaminase levels, nitrosative stress markers, and activities of oxidatively modified mitochondrial proteins were measured.

RESULTS

Comparative 2-dimensional gel analysis revealed markedly increased numbers of oxidized and S-nitrosylated mitochondrial proteins following hepatic I/R injury. Many key mitochondrial enzymes involved in cellular defense, fat metabolism, energy supply, and chaperones were identified as being oxidatively modified proteins. Pretreatment with MnTMPyP attenuated the I/R-induced increased serum transaminase levels, histologic damage, increased inducible nitric oxide synthase expression, and S-nitrosylation and/or nitration of various key mitochondrial proteins. MnTMPyP pretreatment also restored I/R-induced suppressed activities of mitochondrial aldehyde dehydrogenase, 3-ketoacyl-CoA thiolases, and adenosine triphosphate synthase.

CONCLUSIONS

These results suggest that increased nitrosative stress is critically important in promoting S-nitrosylation and nitration of various mitochondrial proteins, leading to mitochondrial dysfunction with decreased energy supply and increased hepatic injury.

S-Adenosylmethionine Exerts a Protective Effect against Thioacetamide-induced Injury in Primary Cultures of Rat Hepatocytes

S-adenosylmethionine (SAMe) has been shown to protect hepatocytes from toxic injury, both experimentally-induced in animals and in isolated hepatocytes. The mechanisms by which SAMe protects hepatocytes from injury can result from the pathways of SAMe metabolism. Unfortunately, data documenting the protective effect of SAMe against mitochondrial damage from toxic injury are not widely available. Thioacetamide is frequently-used as a model hepatotoxin, which causes in vivo centrilobular necrosis. Even though thioacetamide-induced liver necrosis in rats was alleviated by SAMe, the mechanisms of this protective effect remain to be verified. The aim of our study was to determine the protective mechanisms of SAMe on thioacetamide-induced hepatocyte injury by using primary hepatocyte cultures. The release of lactate dehydrogenase (LDH) from cells incubated with thioacetamide for 24 hours, was lowered by simultaneous treatment with SAMe, in a dose-dependent manner. The inhibitory effect of SAMe on thioacetamide-induced lipid peroxidation paralleled the effect on cytotoxicity. A decrease in the mitochondrial membrane potential, as determined by Rhodamine 123 accumulation, was also prevented. The attenuation by SAMe of thioacetamide-induced glutathione depletion was determined after subsequent incubation periods of 48 and 72 hours. SAMe protects both cytoplasmic and mitochondrial membranes. This effect was more pronounced during the development of thioacetamide-induced hepatocyte injury that was mediated by lipid peroxidation. Continuation of the SAMe treatment then led to a reduction in glutathione depletion, as a potential consequence of an increase in glutathione production, for which SAMe is a precursor.

Protective effect of S-adenosylmethionine on cellular and mitochondrial membranes of rat hepatocytes against tert-butylhydroperoxide-induced injury in primary culture

Accumulating evidence that administration of S-adenosylmethionine (SAMe) protects hepatocytes against oxidative stress-mediated injury led us to evaluate the effect of SAMe on hepatocyte injury induced in culture by oxidant substance tert-butylhydroperoxide (1.5 mM tBHP) with regard to prevent mitochondrial injury. The pretreatment of hepatocyte culture with SAMe in doses of 0.25, 0.5, 1, 2.5, 5, 10, 25 and 50 mg/l for 30 min prevented the release of LDH from cells incubated for 30 min with tBHP in a dose dependent manner. The inhibitory effect of SAMe on lipid peroxidation paralleled the effect on cell viability. SAMe also moderated the decrease of the mitochondrial membrane potential induced by tBHP. Our results indicate that the inhibition of lipid peroxidation by SAMe can contribute to the prevention of disruption of both cellular and mitochondrial membranes. While the protective effect of SAMe against tBHP-induced GSH depletion was not confirmed, probably the most potent effect of SAMe on membranes by phospholipid methylation should be verified.

Modulation of endotoxin stimulated interleukin-6 production in monocytes and Kupffer cells by S-adenosylmethionine (SAMe)

Interleukin-6 (IL-6) is a multifunctional cytokine having primarily anti-apoptotic and anti-inflammatory effects. Recent reports have documented that IL-6 plays a key role in liver regeneration. Intracellular deficiency of S-adenosylmethionine (SAMe) is a hallmark of toxin-induced liver injury. Although the administration of exogenous SAMe attenuates liver injury, its mechanisms of action are not fully understood. Here we investigated the effects of exogenous SAMe on IL-6 production in monocytes and Kupffer cells. RAW 264.7 cells, a murine monocyte cell line, and isolated rat Kupffer cells were stimulated with lipopolysaccharide (LPS) in the absence or presence of exogenous SAMe. IL-6 production was assayed by ELISA and intracellular SAMe concentrations were measured by HPLC. We have found that exogenous SAMe administration enhanced both IL-6 protein production and gene expression in LPS-stimulated monocytes and Kupffer cells. Cycloleucine (CL), an inhibitor for extrahepatic methionine adenosyltransferases (MAT), inhibited LPS-stimulated IL-6 production. The enhancement of LPS-stimulated IL-6 production by SAMe was inhibited by ZM241385, a specific antagonist of adenosine (A2) receptor. Our results demonstrate that SAMe administration may exert its anti-inflammatory and hepatoprotective effects, at least in part, by enhancing LPS-stimulated IL-6 production.

Metabolic, antioxidant, nutraceutical, probiotic, and herbal therapies relating to the management of hepatobiliary disorders

Many nutraceuticals, conditionally essential nutrients, and botanical extracts have been proposed as useful in the management of liver disease. The most studied of these are addressed in terms of proposed mechanisms of action, benefits, hazards, and safe dosing recommendations allowed by current information. While this is an area of soft science, it is important to keep an open and tolerant mind, considering that many major treatment discoveries were in fact serendipitous accidents.

Antioxidant properties of S-adenosyl-L-methionine in Fe(2+)-initiated oxidations

S-Adenosylmethionine (SAM) is protective against a variety of toxic agents that promote oxidative stress. One mechanism for this protective effect of SAM is increased synthesis of glutathione. We evaluated whether SAM is protective via possible antioxidant-like activities. Aerobic Hepes-buffered solutions of Fe2+ spontaneously oxidize and consume O2 with concomitant production of reactive oxygen species and oxidation of substrates to radical products, e.g., ethanol to hydroxyethyl radical. SAM inhibited this oxidation of ethanol and inhibited aerobic Fe2+ oxidation and consumption of O2. SAM did not regenerate Fe2+ from Fe3+ and was not consumed after incubation with Fe2+. SAM less effectively inhibited aerobic Fe2+ oxidation in the presence of competing chelating agents such as EDTA, citrate, and ADP. The effects of SAM were mimicked by S-adenosylhomocysteine, but not by methionine or methylthioadenosine. SAM did not inhibit Fe2+ oxidation by H2O2 and was a relatively poor inhibitor of the Fenton reaction. Lipid peroxidation initiated by Fe2+ in liposomes was associated with Fe2+ oxidation; these two processes were inhibited by SAM. However, SAM did not show significant peroxyl radical scavenging activity. SAM also inhibited the nonenzymatic lipid peroxidation initiated by Fe2+ + ascorbate in rat liver microsomes. These results suggest that SAM inhibits alcohol and lipid oxidation mainly by Fe2+ chelation and inhibition of Fe2+ autoxidation. This could represent an important mechanism by which SAM exerts cellular protective actions and reduces oxidative stress in biological systems.

Gadolinium chloride and salvia miltiorrhiza compound ameliorate reperfusion injury in hepatocellular mitochondria

AIM: To investigate the effect of gadolinium chloride (GaCl₃) and salvia miltiorrhiza compound (SMCo) on ischemia and reperfusion (I/R) injury in hepatocellular mitochondria.

METHODS: Wistar rats were randomly to divided into control group, GaCl₃ group, SMCo group and GaCl₃ + SMCo group (n = 15 each). GaCl₃ (7 mg·kg^-1) was injected into tail vein on d 1 and d 2 in contrast group. SMCo (2 mL·kg^-1) was injected into muscle on d 1 and d 2 in SMCo group. GaCl₃ + SMCo group received both GaCl₃ (iv) and SMCo (im) injection. Control group received saline injection only. On d 3, all the rats were subjected to 2 h ischemia in the middle and left lobes of the liver, followed by reperfusion for 2 h, 6 h and 18 h respectively. The level of serum alanine aminotransferase (ALT) and malondialdehyde (MDA) in hepatocellular mitochondria was measured. Pathological changes in hepatic tissue and in hepatocellular mitochondria were determined with optical microscope and electronic microscope, respectively.

RESULTS: Remarkablly pathohistological and biochemical changes were detected after 6 h of I/R. Compared with control, the level of ALT was decreased in GaCl₃, SMCo and GaCl₃ + SMCo treated groups (1314.0 ± 278.7 vs 809.4 ± 196.1, 716.6 ± 242.8 and 837.2 ± 190.6 IU·L^-1, respectively. P < 0.05). Similarly, the level of MDA was decreased in GaCl₃, SMCo and GaCl₃ + SMCo treated groups (293.1 ± 51.1 vs 190.8 ± 55.5, 214.3 ± 32.9 and 221.0 ± 47.3 nmol·g^-1, respectively, P < 0.05). Accordingly, in control group, swelling, degeneration, focal necrosis, infiltration of leucocyte were found in reperfused tissue under an optical microscope, and mitochondria swelling, rupture and even breakdown were seen under an electronic microscope. These pathohistological and ultrastructural damages caused by I/R were greatly attenuated in GaCl₃, SMCo and GaCl₃ + SMCo treated groups. However, there was no additive effect observed when GaCl₃ and SMCo were used together.

CONCLUSION: Both GaCl₃ and SMCo can alleviate the I/R injury in hepatocellular mitochondria.

Characterization of sams genes of Amoeba proteus and the endosymbiotic X-bacteria

As a result of harboring obligatory bacterial endosymbionts, the xD strain of Amoeba proteus no longer produces its own S-adenosylmethionine synthetase (SAMS). When symbiont-free D amoebae are infected with symbionts (X-bacteria), the amount of amoeba SAMS decreases to a negligible level within four weeks, but about 47% of the SAMS activity, which apparently comes from another source, is still detected. Complete nucleotide sequences of sams genes of D and xD amoebae are presented and show that there are no differences between the two. Long-established xD amoebae contain an intact sams gene and thus the loss of xD amoeba's SAMS is not due to the loss of the gene itself. The open reading frame of the amoeba's sams gene has 1,281 nucleotides, encoding SAMS of 426 amino acids with a mass of 48 kDa and pI of 6.5. The amino acid sequence of amoeba SAMS is longer than the SAMS of other organisms by having an extra internal stretch of 28 amino acids. The 5'-flanking region of amoeba sams contains consensus-binding sites for several transcription factors that are related to the regulation of sams genes in E. coli and yeast. The complete nucleotide sequence of the symbiont's sams gene is also presented. The open reading frame of X-bacteria sams is 1,146 nucleotides long, encoding SAMS of 381 amino acids with a mass of 41 kDa and pI of 6.0. The X-bacteria SAMS has 45% sequence identity with that of A. proteus.