Synthesis and pharmacological activity of a novel water-soluble hepatocyte-specific polymeric prodrug of prostaglandin E(1) using lactosylated poly(L-glutamic hydrazide) as a carrier

Non-activated Esters as Reactive Handles in Direct Post-Polymerization Modification

Non-activated esters are prominently featured functional groups in polymer science, as ester functional monomers display great structural diversity and excellent compatibility with a wide range of polymerization mechanisms. Yet, their direct use as a reactive handle in post-polymerization modification has been typically avoided due to their low reactivity, which impairs the quantitative conversion typically desired in post-polymerization modification reactions. While activated ester approaches are a well-established alternative, the modification of non-activated esters remains a synthetic and economically valuable opportunity. In this review, we discuss past and recent efforts in the utilization of non-activated ester groups as a reactive handle to facilitate transesterification and aminolysis/amidation reactions, and the potential of the developed methodologies in the context of macromolecular engineering.

The Hepato-protective Effects of Portulaca oleracea L. extract: Review

BACKGROUND

Portulaca oleracea L. (Purslane) has been used in traditional medicine against hepatic injury, although its actual efficacy has not been fully understood. The present study aimed to critically review the recent literature data from 1990 to 2017 regarding the hepato-protective effects of Portulaca oleracea L. and its underlying mechanisms.

METHODS

Online literature resources were checked using different search engines such as Medline, PubMed, Iran Medex, Scopus, and Google Scholar to identify articles, editorials, and reviews about antidotal effects of Portulaca oleracea L. against hepatotoxic agents.

RESULTS

Few studies have indicated that Portulaca oleracea L. shows protective effects against hepatotoxic agents. However, due to lack of information in humans, more studies are needed to confirm the efficacy of Portulaca oleracea L. as a hepato-protective agent.

CONCLUSION

The study found that Portulaca oleracea L. may be effective on hepatotoxicity by modulating oxidative stress and inflammation.

Protective effect and mechanism of ginsenoside Rg1 on carbon tetrachloride‑induced acute liver injury

Liver injury is a common pathological state in various types of liver disease; severe or persistent liver damage is the basis of hepatic failure. Ginsenoside Rg1 (Rg1), one of the primary active ingredients of ginseng, has been reported to reduce concanalin A‑induced hepatitis and protect against lipopolysaccharide‑ and galactosamine‑induced liver injury. However, the underlying protective mechanism of Rg1 in acute liver injury remains unclear. In the present study, a carbon tetrachloride (CCl4)‑induced acute liver injury model was established, and the protective effect of Rg1 on CCl4‑induced acute liver injury was demonstrated in cell culture and animal experimental systems. Further investigation of the mechanisms demonstrated that pretreatment with Rg1 reduced elevated levels of alanine aminotransferase and aspartate aminotransferase, enhanced the antioxidant activity of superoxide dismutase (SOD) and decreased malondialdehyde (MDA) content. Experiments in vitro demonstrated that Rg1 decreased p65 expression and inhibited nuclear factor (NF)‑κB activity. In addition to the effect of Rg1, an NF‑κB inhibitor promoted cell survival, enhanced SOD activity and reduced MDA level. It was observed through in vivo experiments that pretreatment with Rg1 inhibited NF‑κB expression and activity in Kupffer cells and reduced the serum levels of tumor necrosis factor‑α and interleukin‑6. In conclusion, the results of the present study indicated that pretreatment with Rg1 may rescue CCl4‑induced acute liver injury in vivo and in vitro through inhibition of NF‑κB activity, to restore the anti‑oxidative defense system and down‑regulate pro‑inflammatory signaling pathways. The present observations provide a theoretical foundation for the clinical application of Rg1 therapy in acute liver injury.

Liver-targeting of primaquine-(poly-γ-glutamic acid) and its degradation in rat hepatocytes

We have synthesized poly-γ-glutamic acid (PGA) modified with a synthetic trivalent glyco-ligand (TriGalNAc) for the hepatocyte asialoglycoprotein receptor (ASGP-R). We investigated in vivo distribution of unmodified PGA and TriGalNAc-modified PGA (TriGalNAc-PGA) in mice after intravenous injection. Most of unmodified PGA administered was transported to the bladder over 20-80min, suggesting a rapid excretion of unmodified PGA into urine. In contrast, TriGalNAc-PGA was found exclusively in the liver over the same period of time. We further synthesized TriGalNAc-PGA-primaquine conjugate (TriGalNAc-PGA-PQ), and investigated binding, uptake, and catabolism of the conjugate by rat hepatocytes. Our studies indicated that approximately 250ng per million cells of the conjugate bound to one million rat hepatocytes at 0°C, and approximately 2μg per million cells of the conjugate was taken up over 7h incubation at 37°C. Furthermore, our results suggested that TriGalNAc-PGA-PQ was almost completely degraded over 24h, and small degradation products were secreted into cell culture medium. The results described in this report suggest that the TriGalNAc ligand can serve as an excellent targeting device for delivery of PGA-conjugates to the liver hepatocytes, and rat hepatocytes possess sufficient capacity to digest PGA even modified with other substituents.

Pharmacokinetic considerations for targeted drug delivery

Drug delivery systems involve technology designed to maximize therapeutic efficacy of drugs by controlling their biodistribution profile. In order to optimize a function of the delivery systems, their biodistribution characteristics should be systematically understood. Pharmacokinetic analysis based on the clearance concepts provides quantitative information of the biodistribution, which can be related to physicochemical properties of the delivery system. Various delivery systems including macromolecular drug conjugates, chemically or genetically modified proteins, and particulate drug carriers have been designed and developed so far. In this article, we review physiological and pharmacokinetic implications of the delivery systems.

Hepatoprotective effect of pinoresinol on carbon tetrachloride-induced hepatic damage in mice

Forsythiae Fructus is known to have diuretic, anti-bacterial, and anti-inflammatory activities. This study examined the hepatoprotective effects of pinoresinol, a lignan isolated from Forsythiae Fructus, against carbon tetrachloride (CCl(4))-induced liver injury. Mice were treated intraperitoneally with vehicle or pinoresinol (25, 50, 100, and 200 mg/kg) 30 min before and 2 h after CCl4 (20 microl/kg) injection. In the vehicle-treated CCl(4 )group, serum aminotransferase activities were significantly increased 24 h after CCl4 injection, and these increases were attenuated by pinoresinol at all doses. Hepatic glutathione contents were significantly decreased and lipid peroxidation was increased after CCl4 treatment. These changes were attenuated by 50 and 100 mg/kg of pinoresinol. The levels of protein and mRNA expression of inflammatory mediators, including tumor necrosis factor-alpha, inducible nitric oxide synthase, and cyclooxygenase-2, were significantly increased after CCl4 injection; and these increases were attenuated by pinoresinol. Nuclear translocation of nuclear factor-kappaB (NF-kappaB) and phosphorylation of c-Jun, one of the components of activating protein 1 (AP-1), were inhibited by pinoresinol. Our results suggest that pinoresinol ameliorates CCl4)-induced acute liver injury, and this protection is likely due to anti-oxidative activity and down-regulation of inflammatory mediators through inhibition of NF-kappaB and AP-1.

Water-soluble HPMA copolymer—prostaglandin E1conjugates containing a cathepsin K sensitive spacer

A novel bone targeting, N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer based, prostaglandin E1 (PGE1) delivery system was designed, synthesized and characterized. PGE1 was bound to the polymer backbone via a spacer, composed of a cathepsin K sensitive tetrapeptide (Gly-Gly-Pro-Nle) and a self-eliminating 4-aminobenzyl alcohol structure. The HPMA copolymer conjugates were prepared by photo-initiated free radical copolymerization of HPMA, PGE1-containing macromonomer, and optionally a comonomer containing a reactive p-nitrophenyl ester group. The latter group was used as attachment points for the D-aspartic acid octapeptide targeting moieties. Incubation of the PGE1-containing macromonomer and HPMA copolymer-PGE1 conjugates with cathepsin K resulted in release of unmodified PGE1. The rate of release depended on the composition of the conjugate. The higher the PGE1 content in the conjugate, the slower the PGE1 release. This appeared to be the result of association of hydrophobic side-chains in aqueous media, which rendered the formation of the enzyme substrate complex more difficult. The data seems to indicate that HPMA copolymer-PGE1 conjugates have a potential in the treatment of osteoporosis and other bone diseases.

Prostaglandin E1 combined with plasma exchange for treatment of patients with severe hepatitis: an analysis of 33 cases

AIM: To evaluate the therapeutic effects of prostaglandin E1 (PGE1) combined with plasma exchange in patients with severe hepatitis.

METHODS: Sixty-two patients with severe hepatitis were randomly divided into treatment (n = 33) and control (n = 29) groups. In the treatment group, 33 patients with severe hepatitis (two with subacute severe hepatitis, and 31 with chronic severe hepatitis) received combined therapy with comprehensive internal medicine treatment which was the artificial liver support system and PGE1. In the control group, 29 patients (one with subacute severe hepatitis, and 28 with chronic severe hepatitis) were treated with comprehensive internal medicine and the artificial liver support system.

RESULTS: After treatment, serum total bilirubin, alanine aminotransferase, and PTA were significantly improved in the two groups. There were significant differences between the treatment and control group in concentration of TBIL and PTA (155.8 ± 138.2 µmol/L vs 296.4 ± 100.5 µmol/L; 62.6% ± 10.4% vs 42.9% ±11.4%; P < 0.01). The survival rate in the treatment group was higher than that in the control group (72.8% vs 48.3%, P < 0.01).

CONCLUSION: PGE1 combined with plasma exchange is an effective method for treating severe hepatitis.

Liver targeting of catalase by cationization for prevention of acute liver failure in mice

To achieve hepatic delivery of CAT for the prevention of CCl4-induced acute liver failure in mice, two types of cationized CAT derivatives, HMD- and ED-conjugated CAT, were developed. Slight structural changes occurred during cationization and the number of increased free amino groups was 3.1 in HMD-CAT and 13.6 in ED-CAT. 111In-cationized CAT derivatives showed an increased binding to HepG2 cells, and were rapidly taken up by the liver. H2O2-induced cytotoxicity in HepG2 cells was significantly prevented by preincubation of the cells with cationized CAT derivatives. A bolus intravenous injection of the cationized CAT derivatives reduced the hepatotoxicity induced by CCl4 in mice. The ED-CAT, which showed more rapid and greater binding to the liver than the HMD-CAT, exhibited more beneficial effects as far as all the parameters examined (serum GOT, GPT, LDH and hepatic GSH) were concerned, suggesting that a high degree of cationization is effective in delivering CAT to the liver to prevent CCl4-induced hepatotoxicity. These results suggest that cationized CAT derivatives are effective in preventing acute liver failure, and ED-based cationization is a suitable method for developing liver-targetable cationized CAT derivatives, because it provides CAT with a high degree of cationization and a high remaining enzymatic activity.

Novel delivery methods for treatment of viral hepatitis: an update

Viral hepatitis represents the most common cause of chronic liver disease worldwide. Currently approved therapies for chronic hepatitis B include IFN, an immune modulator, and nucleoside analogues lamivudine and adefovir. For chronic hepatitis C, a combination of pegylated IFN-alpha and ribavirin represents the standard treatment. However, currently available treatments for both these viruses are effective only in a limited number of patients, are costly, prolonged, associated with significant side effects and require a substantial commitment from the patients and healthcare providers. A number of novel antiviral treatments, together with strategies to enhance the response to current therapies, are being explored at present. For all new therapies, as well as for improving existing treatments, selective delivery of medications into liver cells would be desirable to enhance antiviral activity and avoid systemic side effects. New achievements in the field of drug and gene delivery against chronic hepatitis to the liver are reviewed here.

Cationic charge-dependent hepatic delivery of amidated serum albumin

To obtain a quantitative correlation between the physicochemical properties of amidated bovine serum albumin (BSA) and their tissue distribution characteristics for the development of targeted delivery of proteins, BSA was amidated with hexamethylenediamine (HMD) or ethylenediamine (ED) to obtain cationized BSAs. Their structural changes were examined by spectroscopic and electrophoretic techniques then their tissue distribution was studied in mice. Circular dichroism (CD) and fluorescence measurements showed that spectroscopic changes occurred as the number of free NH2 groups increased. Capillary electrophoresis revealed a linear relationship between the mobility and the increased number of free NH2 groups. 111In-cationized BSAs were rapidly taken up by liver, but HMD-BSA showed a faster uptake than ED-BSA with a similar number of free NH2 groups, suggesting that the diamine reagent with a longer carboxyl side chain results in more efficient hepatic targeting. The hepatic uptake clearance (CL(liver)) of both derivatives increased significantly with a decrease in electrophoretic mobility (mu(ep)) towards the anode and reached a plateau at low electrophoretic mobility. The electrophoretic mobility is an appropriate indicator of the degree of amidation, which was closely correlated with the hepatic uptake clearance. The correlation between the mobility and the clearance shows that a low degree of amidation is sufficient for efficient hepatic targeting of proteins.

Development of cell-specific targeting systems for drugs and genes

Cell-specific targeting systems for drugs and genes have been developed by using glycosylated macromolecule as a vehicle that can be selectively recognized by carbohydrate receptors. Pharmacokinetic analyses of the tissue distribution of glycosylated proteins came to the conclusion that the surface density of the sugar moiety on the protein derivative largely determines the binding affinity for the receptors and plasma lectin. Many glycosylated delivery systems have been developed and their usefulness investigated in various settings. Galactosylated polymers, when properly designed, were found to be effective in delivering prostaglandin E1 and other low-molecular-weight drugs selectively to hepatocytes. In addition, glycosylated superoxide dismutase and catalase were successfully developed with minimal loss of enzymatic activity. A simultaneous targeting of these two enzymes to liver nonparenchymal cells significantly prevented hepatic ischemia/reperfusion injury. On the other hand, galactosylated catalase, a derivative selectively delivered to hepatocytes, effectively inhibited hepatic metastasis of colon carcinoma cells in mice. Finally, hepatocyte-targeted in vivo gene transfer was achieved by synthesizing a multi-functional carrier molecule, which condenses plasmid DNA, delivering DNA to hepatocytes through recognition by asialoglycoprotein receptors, and releasing DNA from endosomes/lysosomes into cytoplasm.

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