-
[show abstract]
[hide abstract]
ABSTRACT: To determine the potential of the high mobility group box-1 protein 1 (HMGB1) to activate Toll-like receptor 4 (TLR4) signaling in hepatic stellate cells (HSCs) and investigate the subsequent transition of HSC towards the inflammatory phenotype. Three immortalized mouse HSC cell lines, wild-type (JS1), TLR4-/- (JS2) and MyD88-/- (JS3), were subcultured in plates and divided into groups of normal control (untreated), postive control (lipopolysaccaride, LPS treatment), and experimental (HMGB1 treatment). All groups were transfected with luciferase reporter plasmids carrying responsive elements for either the nuclear factor-kappa B (NF-kB) or activator protein-1 AP-1 transcription factors. Following stimulation with normal saline, LPS (100 ng/mL) or HMGB1 (100 ng/mL), the activation of NF-kB or AP-1 was detected by a dual-luciferase reporter assay system. The induction of monocyte chemotactic protein-1 (MCP-1) transcription was determined by measuring the mRNA levels using real time quantitative reverse transcription PCR (qRT-PCR). The secreted protein levels of MCP-1 were determined by enzyme-linked immunosorbent assay (ELISA) of the culture supernatants. Activation of NF-kB- and AP-1-responsive reporters was significantly up-regulated in JS1 cells treated with HMGB1 or LPS, and the activation was coincident with markedly up-regulated transcription and secretion of MCP-1. However, HMGB1 and LPS treatment produced no responsive of the NF-kB and AP-1 reporters, and no increase in expression or secretion of MCP-1, in JS2 or JS3 cells. As an endogeous ligand of TLR4, HMGB1 may activate TLR4 signaling and the TLR4-mediated inflammatory response of HSC.
Zhonghua gan zang bing za zhi = Zhonghua ganzangbing zazhi = Chinese journal of hepatology 08/2012; 20(8):581-4.
-
[show abstract]
[hide abstract]
ABSTRACT: A cirrhosis risk score (CRS) comprised of single nucleotide polymorphisms (SNPs) in seven genes that predicts the risk of cirrhosis in Caucasian hepatitis C has been reported. The present study was to evaluate the association of 11 separate but related SNPs and the CRS with cirrhosis risk in Chinese hepatitis B patients. A total of 563 Chinese subjects with persistent HBV infection (349 with evident liver cirrhosis and 214 without cirrhosis clinically or pathologically) were studied. The candidate SNPs were detected with a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method. The allele frequency and genotype distribution of each polymorphism as well as the CRS value within the cirrhosis and non-cirrhosis subjects were compared. The rs2679757 polymorphism of the antizyme inhibitor 1 (AZIN1) gene was associated with the risk of cirrhosis (x2 = 6.79, P = 0.03, odds ratio for GG+AG versus AA = 1.63, 95% confidence interval = 1.13-2.35). A gene variant (rs886277) in the transient receptor potential cation channel subfamily M, member 5 gene (TRPM5) was associated with liver cirrhosis, but did not reach statistical significance (x2 = 5.77, P = 0.06). Two SNPs (rs4986791, rs62522600) are not polymorphic in Chinese. Genotype frequencies of other SNPs were not different between the cirrhosis and non-cirrhosis groups. The overall CRS values were not different between the cirrhotic and non-cirrhotic groups (median value 0.57 versus 0.62, Z = -1.05, P = 0.29). SNP rs2679757 in the AZIN1 gene is associated with the risk of HBV-related liver cirrhosis in Chinese. The CRS for Caucasian population has limited applicability for predicting liver cirrhosis in Chinese hepatitis B patients. SNPs associated with cirrhosis prognosis in hepatitis B patients and liver diseases with other etiologies warrant further clinical validation.
Zhonghua gan zang bing za zhi = Zhonghua ganzangbing zazhi = Chinese journal of hepatology 03/2011; 19(3):169-73.
-
[show abstract]
[hide abstract]
ABSTRACT: To investigate the role of heme oxygenase(HO), a catalyzing enzyme of heme to produce CO, in modulation of systemic circulation in CCl4-induced cirrhotic rats. Saline(vehicle) and ZnPP were s.c. injected into the posterior necks of rats respectively and the rats were then anesthetized by pentobarbital sodium in four hours. Mean arterial pressure (MAP, kPa), heart rate (HR, b/min) and portal pressure (PP, cm/H2O) were measured by indwelling catheter. Plasma CO was determined by Chalmers method. Heme oxygenase acivity was determined by the rate of bilirubin formation. The cirrhotic rats showed significant hyperdynamic circulation indicated by decreased mean arterial pressure [MAP, (15.6+/-1.7) vs (18.9+/-0.9) kPa, t = 4.52, P less than 0.01] and increased portal pressure [PP, (16.7+/-0.8) vs (8.8+/-0.3) cm H2O, t = 23.10, P less than 0.01] as compared to normal control rats(NS). ZnPP could cause a significant increase in MAP [(17.3+/-1.5) vs (15.6+/-1.7) kPa, t = 2.18, P less than 0.05] and significant decrease in PP [(13.2+/-0.7) vs (16.7+/-0.8) cm H2O, t = 8.53, P less than 0.01] in cirrhotic rats. The cirrhotic group presented a significant increase in plasma CO [(18.0+/-1.9) vs (10.4+/-1.3)mumol/L, t = 8.42, P less than 0.01] and HO activity in the spleens [(11.1+/-0.9) vs (6.5+/-0.9) nmol bilirubin/mg protein/h, t = 9.28, P less than 0.01] and intestines [(2.5+/-0.1) vs. (1.3+/-0.2) nmol bilirubin/mg protein/h, t = 15.1, P less than 0.01]. ZnPP could cause significant decreases in plasma CO and HO activity in liver, spleen and intestine of both control and cirrhotic rats. HO-CO system activation may be an important reason for the hemodynamic disturbance of liver cirrhosis.
Zhonghua gan zang bing za zhi = Zhonghua ganzangbing zazhi = Chinese journal of hepatology 03/2011; 19(3):174-7.
-
Zhonghua gan zang bing za zhi = Zhonghua ganzangbing zazhi = Chinese journal of hepatology 08/2010; 18(8):566-8.
-
Zhonghua gan zang bing za zhi = Zhonghua ganzangbing zazhi = Chinese journal of hepatology 02/2010; 18(2):158-60.
-
[show abstract]
[hide abstract]
ABSTRACT: ABSTRACT—Aims/Background: Potenlini is an injectable compound whose active component is glycyrrhizin, which is extracted from licorice. Previous studies showed that it could reduce liver injury, improve alanine aminotransferase (ALT) levels and act as an antifibrotic agent. However, the mechanism of its action remains unclear. The aim of this study was to determine the molecular mechanism of its action by investigating the effects of potenlini on nuclear factor-κB(NF-κB) binding activity in an animal model of liver cirrhosis. Methods: Rats were randomly allocated into a normal control group, a model control group, and a potenlini group. Rats in the latter two groups were treated with CCl4 and ethanol solution in order to induce chronic liver injury. Rats in the potenlini group were given potenlini treatment at the same time. Results: Serum ALT levels were significantly reduced in rats treated with potenlini compared with levels in rats of the model control group, which had dramatically increased ALT levels. Histologically, liver steatosis and fibrosis were severe in the rats of the model group, but were significantly improved in rats of the potenlini group. NF-κB binding activity was markedly increased in the liver specimens taken from the rats of the model control group in comparison with the binding of normal livers, but the binding levels were nearly normal in the livers of the potenlini group. Conclusions: The results suggest that potenlini can inhibit the NF-κB binding activity in CCl4 and ethanol-induced chronic liver injury, and that effect may be a possible mechanism by which potenlini protects the liver from hepatotoxin-induced liver injury and cirrhosis.
Liver International 12/2008; 18(3):180 - 185.
-
[show abstract]
[hide abstract]
ABSTRACT: To screen highly efficient small interfering RNA (siRNA) targeting human cyclooxygenase-2 (hCOX-2) mRNA on human rheumatoid arthritis synovial fibroblasts (RASF) and to further study the impact there on prostaglandin E2 (PGE2) and cytokines, such as interleukin-1beta (IL-1beta), interleukin-6 (IL-6), timorous necrosis factor-alpha (TNF-alpha), and vascular endothelial growth factor (VEGF).
4 lines of COX-2 mRNA siRNA (1(#) - 4(#) siRNA) were designed and transfected into the fibroblasts from the synovial membrane of a patient with rheumatoid arthritis (RASF). Phorbol ester was added 4 hours later. A scrambled line (NC) group and a blank control (CTL) group were used. RT-PCR and Western blot ting were used to detect the mRNA and protein expression of COX-2 36 and 48 hours after transfection. The levels of PGE2, IL-1beta, IL-6, TNF-alpha, and VEGF were measured by ELISA.
RT-PCR showed that the absorbance ratios of the positively interfering groups, NC, and 1(#) - 3(#) siRNA groups, to CTL group were 0.72, 0.3, 0.25, 0.4, and 0.04 respectively. The ratios of the positively interfering groups to CTL group were 1.04, 0.52, 0.39, 0.9, and 36 h after transfection and 1.05, 0.52, 0.51, 0.9, and 0.15 respectively 48 h after transfection. The levels of PGE2, IL-1beta, IL-6, TNF-alpha, and VEGF in the culture supernatant were lower in the 4(#) siRNA group than in other groups 24, 36, and 48 h after transfection. The death rates of RASF of all trial groups were within the range of 9% - 11% and there were not statistically significant differences between the CTL group and the siRNA groups or between the 4(#) siRNA and other siRNA groups.
4(#) siRNA effectively inhibits the expression of COX-2 mRNA and protein the level of PGE2, IL-1beta, IL-6, TNF-alpha, and VEGF in the clear supernatant of the 4(#) group is lowest.
Zhonghua yi xue za zhi 12/2007; 87(41):2925-8.
-
[show abstract]
[hide abstract]
ABSTRACT: Upregulation of cyclooxygenase-2 (COX-2), an inducible enzyme that is actively involved in inflammation and wound healing, has been found in cirrhotic livers. The aim of this study was to investigate the effects of selective inhibition of COX-2 on the development of liver cirrhosis and portal hypertension in rats.
Liver cirrhosis was induced by carbon tetrachloride (CCl(4)) in Sprague-Dawley rats. Rofecoxib, a highly selective COX-2 inhibitor, was orally administered to rats at a dose of 10 mg/kg/day. Portal pressure was measured at 8 weeks post CCl(4) administration with the catheterization method followed by the harvesting of liver samples. Liver histopathology was analyzed with hematoxylin and eosin and Masson's trichrome staining. The activated, alpha smooth muscle actin (alpha-SMA) positive hepatic stellate cells (HSCs) and the protein levels of collagen types I, III, IV, as well as laminin and two fibrogenic mediators, vascular endothelial growth factor (VEGF) and connective tissue growth factor (CTGF) in the livers, were detected with immunohistochemical staining and western blot methods, respectively. The level of hepatic thromboxane B(2) (TXB(2)), a potent vasoconstrictive substance derived from COX, was measured with enzyme immunoassay.
Oral administration of rofecoxib decreased portal pressure in rats that were treated with CCl(4) for 8 weeks. This was associated with a marked reduction in collagen accumulation and TXB(2) level in the rat livers. In addition, rofecoxib administration was found to reduce the number of activated HSCs and to downregulate hepatic protein levels of three detected types of collagen, laminin, VEGF and CTGF in CCl(4)-treated rats.
COX-2 is involved in the fibrogenesis of livers and the formation of portal hypertension in CCl(4)-treated rats. Selective inhibition of COX-2 by rofecoxib reduces portal hypertension and this is associated with antifibrotic activity as well as a reduction of COX-2-derived vasoactive substance.
Journal of Gastroenterology and Hepatology 07/2007; 22(6):877-84. · 2.87 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Nitric oxide synthases (NOS) and cyclooxygenase-2 (COX-2) are important enzymes involved in ulcer healing but interactions between them have not been clearly defined. The aim of this study was to investigate the effects of selective or non-selective inhibition of NOS on the expression and activity of COX-2 during healing of acetic acid-induced gastric ulcers in rats. N-[3-(aminomethyl)benzyl] acetamidine (1400 W), a potent selective inhibitor of inducible nitric oxide synthase (iNOS), at a dose of 0.1 mg/kg/day, was found to reduce the ulcer sizes at day 3 and 7 post-ulcer induction. On the other hand, 15 mg/kg/day of NG-nitro-L-arginine methyl ester (L-NAME), a non-selective NOS inhibitor that suppresses both iNOS and endothelial nitric oxide synthase (eNOS), enlarged the ulcer sizes over the same time periods. The expression of COX-2 and COX activity, together with NF-kappaB activation in the ulcer tissues were down-regulated by L-NAME but not 1400 W. It is concluded that iNOS may contribute to ulcer formation while COX-2 and eNOS promote ulcer healing. eNOS enhances COX-2 expression possibly through the activation of NF-kappaB.
European Journal of Pharmacology 06/2006; 536(3):301-8. · 2.52 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The present study was to investigate the roles of cyclooxygenase-1 and -2 (COX-1 and COX-2) and prostaglandin (PG) on gastric mucosal integrity of partially sleep deprived (PSD) rats. A slowly moving drum was used to induce PSD. The PG levels in the gastric mucosa of PSD rats, with or without indomethacin or rofecoxib treatment, were determined. Exogenous prostaglandin E (PGE) analog, misoprostol, was administered to PSD rats to investigate the modulating effect of PG in indomethacin-induced gastric damage. It was observed that COX-1 mRNA and protein were up-regulated in the gastric mucosa of PSD rats. Selective COX-2 inhibition by rofecoxib failed to decrease mucosal PGE2 levels nor to affect mucosal integrity in both PSD and sleep undisturbed rats. However, indomethacin, a COX-1 preferential non-selective COX inhibitor, significantly reduced mucosal PGE2 content and produced more severe mucosal damage in PSD rats than in the controls. The deleterious effect of indomethacin on gastric mucosal integrity of PSD rats was significantly attenuated with the administration of misoprostol. These results suggest that PSD enhances COX-1 biosynthesis of gastroprotective PGE2 as an adaptive response of the stomach to stress. The administration of non-selective COX inhibitors to subjects with chronic sleep deprivation may induce more gastric damages.
Pharmacology Biochemistry and Behavior 12/2005; 82(3):515-21. · 2.53 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The gastric mucosa is most susceptible to stress that has been shown to induce mucosal damage in humans and animals. This study aims to explore the underlying mechanisms of partial sleep deprivation, as a source of psychophysiological stress, on gastric functions and its effect on mucosal integrity. Sprague-Dawley rats were partially sleep deprived (PSD) for 7 or 14 days by housing inside slowly rotating drums. Gastric tissues and plasma were sampled at the end of the sleep deprivation periods and mucosal lesion scores were evaluated. Morphological examination was performed after Hematoxylin and Eosin staining. Plasma levels of noradrenaline, adrenaline, gastrin, histamine and somatostatin were determined with enzyme immunoassays. Gastric acidity was measured with acid-base titration in pylorus ligated rats. Gastric mucosal blood flow was evaluated with Laser Doppler Flowmetry. It was found that gastric lesions were induced in about 30%-50% of the PSD rats. Gastric acidity as well as plasma levels of noradrenaline, gastrin and histamine were elevated. Gastric mucosal blood flow and plasma somatostatin level were on the contrary reduced, especially in rats with PSD for 14 days. It is concluded that partial sleep deprivation compromises gastric mucosal integrity by increasing gastric acidity, plasma levels of noradrenaline, gastrin, histamine, and decreasing gastric mucosal blood flow. These results provided experimental evidence on the gastric damaging effects of PSD and it could be one of the risk factors contributing to gastric ulcer formation.
Life Sciences 06/2005; 77(2):220-9. · 2.53 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: In this study, the effects of Centella asiatica water extract (CE) and its active constituent, asiaticoside (AC), on the expression and activity of inducible nitric oxide synthase (iNOS) during gastric ulcer healing in rats were investigated. CE was prepared from Centella asiatica dry plant and the concentration of AC in CE was quantitatively determined with the use of high performance liquid chromatography analysis. Different concentrations of CE (0.10 g/kg and 0.25 g/kg) and AC (5 mg/kg and 10 mg/kg) were orally administered to rats with acetic acid-induced gastric ulcers. They were found to reduce the size of the ulcers at days 1, 3 and 7 after ulcer induction in a dose-dependent manner, with a concomitant attenuation of iNOS activity and protein expression at the ulcer tissues. The levels of nitrite and nitrate (NO(X)-), the stable end-products of nitric oxide (NO), in the gastric ulcer tissues were also decreased. N-[3-(aminomethyl)benzyl]acetamidine (1400W), a highly selective inhibitor of iNOS, was found to produce similar but more potent inhibition on iNOS activity at a dose of 0.1 mg/kg. These findings indicate that CE and AC have an anti-inflammatory property that is brought about by inhibition of NO synthesis and thus facilitates ulcer healing.
Planta Medica 01/2005; 70(12):1150-4. · 2.15 Impact Factor
-
Zhonghua gan zang bing za zhi = Zhonghua ganzangbing zazhi = Chinese journal of hepatology 05/2004; 12(4):242.
-
[show abstract]
[hide abstract]
ABSTRACT: In this study, the healing effects of Centella asiatica water extract (CE) and asiaticoside (AC), an active constituent of CE, on acetic acid induced gastric ulcers (kissing ulcers) in rats were examined. CE was prepared from Centella asiatica dry plant and the concentration of AC in CE was quantitatively determined with the use of high performance liquid chromatography analysis. Different concentrations of CE and AC were orally administered to rats with kissing ulcers. They were found to reduce the size of the ulcers at day 3 and 7 in a dose-dependent manner, with a concomitant attenuation of myeloperoxidase activity at the ulcer tissues. Epithelial cell proliferation and angiogenesis were on the other hand promoted. The expression of basic fibroblast growth factor, an important angiogenic factor, was also upregulated in the ulcer tissues in rats treated with CE or AC. These results further suggest the potential use of Centella asiatica and its active ingredient as anti-gastric ulcers drugs.
Life Sciences 04/2004; 74(18):2237-49. · 2.53 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: To explore the roles of nitric oxide synthase (NOS), heme oxygenase (HO) and cyclooxygenase (COX) in gastric ulceration and to investigate the relationships of the expression and activities of these enzymes at different stages of gastric ulceration.
Gastric ulcers (kissing ulcers) were induced by luminal application of acetic acid. Gastric tissue samples were obtained from the ulcer base, ulcer margin, and non-ulcerated area around the ulcer margin at different time intervals after ulcer induction. The mRNA expression and protein levels of inducible and constitutive isoforms of NOS, HO and COX were analyzed with RT-PCR and Western blotting methods. The activities of the total NOS, inducible NOS (iNOS), HO, and COX were also determined.
Differential expression of inducible iNOS, HO-1 and COX-2 and enzyme activities of NOS, HO and COX were found in the gastric ulcer base. High iNOS expression and activity were observed on day 1 to day 3 in severely inflamed ulcer tissues. Maximum expressions of HO-1 and COX-2 and enzyme activities of HO and COX lagged behind that of iNOS, and remained at high levels during the healing phase.
The expression and activities of inducible NOS, HO-1 and COX-2 are found to be correlated to different stages of gastric ulceration. Inducible NOS may contribute to ulcer formation while HO-1 and COX-2 may promote ulcer healing.
World Journal of Gastroenterology 09/2003; 9(8):1767-71. · 2.47 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The present study was conducted to test the hypothesis that the introduction of the collagenase gene into tissue culture cells and into a rat model of liver fibrosis would result in the expression of enzymatically active product.
FLAG-tagged full-length rat collagenase cDNA was PCR amplified and cloned into a mammalian expression vector. NIH3T3 cells were then transiently transfected with this construct. Expression of exogenous collagenase mRNA was assessed by RT-PCR, and the exogenous collagenase detected by Western blotting using anti-FLAG monoclonal antibody. Enzymatic activity was detected by gelatin zymography. To determine the effects of exogenous collagenase production in vivo, the construct was bound to glycosyl-poly-L-lysine and then transduced into rats that had developed liver fibrosis as a result of CCl(4) plus ethanol treatment. The hepatic expression of the construct and its effect on the formation of liver fibrosis were demonstrated using RT-PCR and immunohistochemistry.
It was found that exogenously expressed rat collagenase mRNA could be detected in NIH3T3 cells following transfection. Enzymatically active collagenase could also be detected in the culture medium. The recombinant plasmid was also expressed in rat liver after in vivo gene transfer. Expression of exogenous rat collagenase correlated with decreased deposition of collagen types I and III in the livers of rats with experimentally induced liver fibrosis.
The expression of active exogenous rat collagenase could be achieved in vitro and in vivo. It was suggested that in vivo expression of active exogenous collagenase may have therapeutic effects on the formation of liver fibrosis.
World Journal of Gastroenterology 11/2002; 8(5):901-7. · 2.47 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Selective cyclooxygenase-2 (COX-2) inhibitors have been shown to produce fewer gastrointestinal adverse reactions when compared with conventional nonselective nonsteroidal anti-inflammatory drugs and they suppress angiogenesis in tumors. The purpose of the present study was to investigate the effects of highly selective COX-2 inhibitor on angiogenesis and protein expression of angiogenic factor during gastric ulcer healing. Gastric ulcers were induced in male Sprague-Dawley rats by a luminal application of acetic acid solution. Rofecoxib, a selective COX-2 inhibitor, was administered at a dose of 10 mg/kg/day by gastric intubation for 14 successive days. The ulcer size was measured at different time intervals after ulcer induction. The microvessels that were immunohistologically positive for von Willebrand factor within the ulcer bed were counted. The protein levels of basic fibroblast growth factor (bFGF) and concentration of prostaglandin E(2) (PGE(2)) in the ulcer tissues were analyzed with Western blotting and immunoassay methods, respectively. The results demonstrated that rofecoxib treatment significantly increased the ulcer size at days 6, 10, and 15. It decreased the number of microvessels, bFGF protein expression, and PGE(2) level in the ulcer base at day 6. The findings that highly selective COX-2 inhibitor delayed ulcer healing in rats and impaired angiogenesis in the ulcer base raise cautions regarding the use of COX-2 inhibitors in patients with gastric ulcers.
Toxicology and Applied Pharmacology 09/2002; 183(1):41-5. · 4.45 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: AIM:To compare the effects of intravenous route and peritoneal route on liver targeted uptake and expression of plasmid delivered by galactose-terminal glyco-poly-l-lysine (G-PLL).METHODS:The plasmid pTM/MMP-1 which could be expressed in eukaryotic cells was bound to G-PLL, and was then transferred into Wistar rats by intravenous and intraperitoneal injection. The expression and distribution of the plasmid were observed at different time periods by in situ hybridization and immunohistochemistry.RESULTS:The plasmid could be expressed significantly within 24 h after being transferred in vivo by both intravenous and intraperitoneal routes. One week later the expression began to decrease, and could still be observed three weeks later. Although both the intravenous and intraperitoneal route could target-specifically deliver the plasmid to the liver, the effect of the former was better as compared to that of the latter.CONCLUSION:Intravenous route is better for liver targeted uptake and expression of G-PLL-bound plasmids than the peritoneal route.
World Journal of Gastroenterology 09/2000; 6(4):508-512. · 2.47 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: AIM:To compare the effects of liposomes and glyco-poly-L-lysine on liver targeted uptake and expression of plasmid in rat liver.METHODS:After binding with lipofectamine or galactose-terminal glyco-poly-l-lysine, the plasmid could be expressed in eukaryotic cells when injected in to Wistar rats by intravenous route. At different time intervals after the injection, the distribution and expression of the plasmid in liver of rats were observed and compared using in situ hybridization and immunohistochemistry.RESULTS:The expression of the plasmidbinding to liposomes or G-PLL cou ld be markedly observed 24 h later, and began to decrease one week later,but it still could be observed up to three weeks.Both liposomes and G-PLL coul d deliver the plasmid to the liver effectively, but the effect of the latter was better than the former concerning the distribution and expression of the plasmid targeted uptake in the liver.
World Journal of Gastroenterology 09/2000; 6(4):526-531. · 2.47 Impact Factor
