PolyG mitigates silica-induced pulmonary fibrosis by inhibiting nucleolin and regulating DNA damage repair pathway.

Polyguanylic acid potassium salt (PolyG) has an anti-fibrotic G-quadruplex (G4) structure. It could inhibit the expression of nucleolin, a protein involved in cell proliferation and apoptosis. However, its role in regulating nucleolin in silicosis is still unknown. After instillation of 50 µl of crystalline silica suspension (50 mg/ml) into the trachea of C57BL/6 mice, we show that nucleolin expression is upregulated in mouse pulmonary tissue following the treatment with silica and that PolyG, which were injected 2.5 mg/kg body weight into mice by abdomen, could alleviate pulmonary fibrosis through inhibiting the expression of nucleolin. Further, we demonstrated that the expression of the DNA double-strand break (DSB) marker, γ-H2AX, increased in response to silica treatment. PolyG could efficiently reduce the protein expression of γ-H2AX and decreased the level of fibrosis-related genes, such as Col1a1 and Col3a1, as well as the levels of fibrosis-associated proteins α-SMA and vimentin in the lungs of silica-treated mice. These findings show that PolyG could regulate nucleolin and DNA damage repair to control fibrotic response in experimental silicosis and provide a new target for preventive intervention.

Therapeutic effects of scavenger receptor MARCO ligand on silica-induced pulmonary fibrosis in rats.

Pulmonary fibrosis induced by prolonged exposure to silica particles is a chronic and irreversible lung disease without effective treatment till now. Our previous study has shown that early intervention with MARCO antagonist PolyG could alleviate pulmonary fibrosis in silica-exposed rats. However, the therapeutic effects of PolyG on silica-induced pulmonary fibrosis have rarely been reported. In this study, we explored the effects of administration (on the 28th day after silica exposure) of PolyG (MARCO inhibitor) on an established rat silicosis model. The lungs were analyzed histopathologically in rats using HE and Masson staining. The silica-induced ERS-related apoptosis, EMT and fibrosis were evaluated using western blotting, qRT-PCR and immunohistochemical analyses. The results suggested that silica exposure could increase the MARCO activity, and induce ERS and EMT in lung tissues. Pharmacological targeting of MARCO with PolyG attenuated the development of pulmonary fibrosis in silica-exposed rats. Further study indicated that PolyG could inhibit silica-induced ERS-related apoptosis and EMT process. Together, our findings reveal an essential function of ERS-related apoptosis and EMT in the processes of pulmonary fibrosis caused by silica, and identify MARCO as a potential therapeutic pharmacological target for silicosis.

Imbalance in the ratio of CpG and polyG contributes to impaired interferon-α expression.

The secretion of interferon-α (IFN-α) is impaired during hepatitis B virus (HBV) infection. DNA sequences purified from distinct viruses, for example, HBV versus members of Herpesviridae, have been shown to differ in their IFN-α signaling properties. The present study found that DNA from HBV inhibited, while DNA from members of Herpesviridae induced, the expression of IFN-α. Furthermore, stimulatory cytosine-phosphate-guanosine (CpG) sequences derived from these DNA viruses could induce the secretion of IFN-α, while inhibitory guanosine-rich oligodeoxynucleoti (polyG) oligonucleotide sequences derived from these DNA viruses could inhibit CpG-induced IFN-α secretion. Using a computational analysis of genomic DNA sequences, the discrimination between the genomes of HBV and those of other DNA viruses that can also cause inflammation of the liver is based on different frequencies of the CpG and polyG motifs. The underrepresentation of stimulatory CpG motifs and overrepresentation of inhibitory polyG motifs were documented in HBV genomes, whereas the DNA from other viral genomes displayed the opposite trend. Moreover, it was demonstrated that HBV could suppress the activation of IFN-α via its own DNA through the high proportion of polyG motifs. To our knowledge, this is the first demonstration of a specific role for polyG motifs in the inhibition of the IFN-α response following DNA virus infection.

Inhibition of MARCO ameliorates silica-induced pulmonary fibrosis by regulating epithelial-mesenchymal transition.

Epithelial-mesenchymal transition (EMT) is linked to fibrosis following exposure to silica. The scavenger receptor, macrophage receptor with collagenous structure (MARCO) plays an important role in silica-induced inflammation, however, the effect of MARCO on silica-induced fibrosis has not been identified. We hypothesized that MARCO would regulate EMT and be involved in the development of silicosis. Herein, we found that MARCO was highly expressed in lung tissue after exposure to silica and a MARCO inhibitor PolyG could alleviate pulmonary fibrosis in vivo. Our results confirmed that the expression of epithelial marker such as E-cadherin decreased, while the expression of mesenchymal markers, including vimentin and α-SMA increased after silica treatment. Furthermore, PolyG administration efficiently blocked the mRNA and protein expression of EMT markers and decreased the level of fibrosis-related transcription factors and proteins, such as Col1a1, Col3a1, Collagen I and Collagen III in the lungs of silica-exposed rats. The findings demonstrate that the macrophage membrane receptor MARCO controls the fibrotic response through regulating EMT in experimental silicosis and suggest a novel target for preventive intervention.

3'poly-G-tailed ODNs inhibit F-spondin to induce cell death and neurite retraction in rat embryonic neurons.

The effects and mechanism of action of oligodeoxyribonucleotides containing CpG motif (CpG-ODNs) on neuron cells are largely unexamined. Here, we found that CpG-A ODNs but not other types of CpG-ODNs induced neurite retraction and cell apoptosis of rat embryonic neurons in a TLR9-independent manner. These effects of CpG-A ODNs were primarily due to the poly-guanosine at the 3' terminus (3'G-ODNs). Pull-down analysis showed that 3'G-ODNs associated with transcription factor Y-BOX1 (YB-1) to facilitate the translocation of YB-1 into the nucleus via the nuclear localizing sequence of YB-1. YB-1 then interacted with the promoter of F-spondin directly at -45 and -1,375 sites as demonstrated by chromatin immunoprecipitation (ChIP) analysis. Binding of YB-1 to F-spondin promoter resulted in downregulation of F-spondin expression. Overexpression of F-spondin rescued the cell death and neurite retraction induced by 3'G-ODNs in embryonic neuron cells. Taken together, these findings suggest that 3'G-ODNs enhance nucleus YB-1 to inhibit F-spondin leading to cell death and neurite retraction of embryonic neuron cells.

Isolation and characterization of cDNAs encoding Ars2 and Pasha homologues, two components of the RNA interference pathway in Litopenaeus vannamei.

The RNA interference (RNAi) is an evolutionarily conserved protective mechanism in eukaryotes against parasitic foreign nucleic acids. Previous studies demonstrated that the RNAi mechanism is important for shrimp antiviral immunity. Here, we report the identification and functional analysis of two key components of the shrimp RNAi activity: Litopenaeus vannamei arsenite resistance gene 2 (LvArs2) and partner of drosha (LvPasha). The full-length cDNA of LvArs2 was 3470 bp, including a 5' untranslated region (UTR) of 167 bp, a 3' UTR of 639 bp, and an open reading frame (ORF) of 2664 bp that encoded 887 amino acid residues with an estimated molecular mass of 102.5 kDa. The full-length cDNA of LvPasha was 2654 bp, including a 5' UTR of 99 bp, a 3' UTR of 560 bp, and an ORF of 1995 bp that encoded 664 amino acid residues with an estimated molecular mass of 74.2 kDa. Co-immunoprecipitation demonstrated that LvArs2 interacted with L. vannamei Dicer2 (LvDcr2) and LvPasha in Drosophila Schneider 2 (S2) cells, suggesting that LvArs2 may be involved in regulation of the miRNA/siRNA pathways in L.vannamei. Subcellular localization assays demonstrated both LvArs2 and LvPasha proteins mainly presented in the nucleus. After Poly(C-G) stimulation, the expression of LvArs2 was suppressed and expression of LvPasha was enhanced in shrimp gills. These results suggest that LvArs2 and LvPasha may participate in the defense against RNA viruses in crustacea.

A murine scavenger receptor MARCO recognizes polystyrene nanoparticles.

Recent toxicological studies indicate that nanoparticles or ultrafine particles (< 100 nm) are more toxic than fine particles (< 2 microm) because of their greater surface area. It is well known that alveolar macrophages play an important role in the first defense against various environmental particles and microorganisms. This is accomplished by binding to a macrophage receptor with collagenous structure (MARCO), one of several scavenger-type receptors expressed on the cell surface of macrophages. MARCO has been shown to mediate the ingestion of unopsonized environmental particles such as TiO(2) and Fe(2)O(3) (1.3 microm in diameter). However, very little is known about the cellular uptake of nanoparticles. In the present study, we investigated whether MARCO mediates the uptake of nanoparticles by using fluorescent-tagged polystyrene particles (20 nm, 200 nm, and 1 microm in diameter). COS-7 cells were transfected with either MARCO cDNA or an empty vector, and the association of the particles with the cells were observed by fluorescence microscopy and atomic force microscopy. MARCO-transfected cells associated with all three sizes of particles in a time-dependent manner, while no obvious binding of particles occurred after 5 h to the empty vector-transfected cells. The uptake of particles by MARCO-transfected cells was partially inhibited by polyG. These results suggest that macrophages associate with nanoparticles (20 nm) at least in part through MARCO and that MARCO plays a role in clearing nanoparticles which can deposit in the alveolar region.

The immunostimulatory activity of CpG oligonucleotides on microglial N9 cells is affected by a polyguanosine motif.

Oligonucleotides (ODN) with hexameric motifs containing central unmethylated CpG dinucleotides are immunostimulatory. Also ODN with continuous guanosines (polyG motif) show a wide range of immunological activity. Depending on the position, the chemical property of the ODN backbone and the cell type, polyG motifs have either an enhancing or a suppressing effect on the immunostimulatory activity of the CpG-ODN. Microglial cells are central components of the innate immune system of the brain and are activated by CpG-ODN in vitro and in vivo. Here we present the analysis of the immunomodulatory effects of CpG-ODN carrying a polyG motif on the microglial cell line N9. Our data show that N9 cells express Toll-like receptor 9 (TLR9) and are activated by CpG-ODN, which leads to expression of interleukin-12p40 (IL12p40), tumor necrosis factor-alpha (TNF-alpha) and inducible nitric oxide synthase (iNOS). A 3'-end polyG motif inhibits phosphothioate (PS) CpG-ODN immunostimulatory activity but enhances the immunostimulatory activity of phosphodiester (PE) CpG-ODN. Correspondingly, a 3'-end polyG motif improves the cellular uptake of PE CpG-ODN but does not change their cellular distribution pattern. Furthermore, PE CpG-ODN with a 3'-end polyG motif interact with a much higher number of cellular proteins than PE CpG-ODN. These data indicate that the 3'-end polyG motif could enhance the immunostimulatory activity of PE CpG-ODN in microglial N9 cells through increasing interaction with cellular proteins. Therefore PE CpG-ODN containing a 3'-end polyG motif resulting in increased immunostimulatory activity might be promising alternate analogues for studies in the central nervous system.

Cell targeting by a generic receptor-targeted polymer nanocontainer platform.

Nanotechnology promises new avenues to medical diagnosis and treatment. Of special interest are injectable nanovehicles that are programmable towards specific targets, are able to evade the immune defense, and are versatile enough to be suited as carriers of complex functionality. Biotin-functionalized (poly(2-methyloxazoline)-b-poly(dimethylsiloxane)-b-poly(2-methyloxazoline) triblock copolymers were self-assembled to form nanocontainers, and biotinylated targeting ligands were attached by using streptavidin as a coupling agent. Specifically, fluorescence-labeled nanocontainers were targeted against the scavenger receptor A1 from macrophages, an important cell in human disease. In human and transgenic cell lines and in mixed cultures, receptor-specific binding of these generic carriers was followed by vesicular uptake. Low nonspecific binding supported the "stealth" properties of the carrier while cytotoxicity was absent. This versatile carrier appears promising for diagnostic or therapeutic medical use.

Induction of intracellular cytokine production in human monocytes/macrophages stimulated with ligands of pattern recognition receptors.

OBJECTIVE: This study addressed the role of the pattern recognition receptors (PRR), which recognize different molecular structures present on microorganisms, apoptotic, senescent and tumor cells, in the stimulation of human monocyte and monocyte-derived macrophages (MDM) for the production of intracellular cytokines. MATERIALS AND METHODS: Monocytes and MDM were stimulated with different ligands of scavenger receptors (SR) and mannose receptor (MR). Production of intracellular cytokines: tumor necrosis factor alpha (TNF alpha), interleukin 10 and 12 (IL-10, IL-12) was determined by flow cytometry following staining with anti-cytokine monoclonal antibodies (mAbs). RESULTS: The ligands of SR type A: fucoidan, polyguanylic acid (polyG), chemically modified low density lipoproteins (LDL), ligands of SR-B: native and chemically modified LDL, and ligand of mannose receptor (MR)-mannan induced strong expression of intracellular TNF alpha and weaker IL-10 in monocytes, while phosphatidylserine (PdS) was without effect. IL-12 was stimulated only by fucoidan and polyG. The induction of cytokine m-RNA generally followed the pattern and the magnitude of intracellular cytokine production. In MDM, intracellular TNF alpha and IL-12 expression was induced by mannan, native and modified LDL, but not other ligands. Expression of IL-10 was less pronounced and occurred following stimulation with fucoidan, polyG and modified, but not native, LDL. CONCLUSIONS: These results suggest that some PRR ligands may be involved in activation of monocytes/MDM for the production of mainly proinflammatory cytokines (TNF alpha, IL-12) implicating their role in the response to microbial and tumor invasion.

The intratumoral application of poly-G-oligodeoxynucleotides does not augment the naturally induced antitumoral CD8-T-cell response in P815 mastocytomas.

DNA sequences containing CpG have been described to induce a strong immune reaction by acting on a variety of immune cells including a strong and pronounced antitumoral response. Poly-G-oligodeoxynucleotides (ODNs) on the other hand have been attributed the preferential induction of CD8-T-cell proliferation when used in vitro. This activity led us to the investigation of the possible antitumoral properties of poly-G-ODNs in an established CD8-dependent tumor eradication model. We used the well described poly-G-ODN 1628 in its capacity to enhance antitumoral CD8 response in the cutaneous mastocytoma P815. When injecting 30 microg of the purified phosphothioate-modified oligo into the tumor bearing area of P815 challenged mice for up to 12 consecutive days we did not observe increased tumor rejection as compared to the group of mice injected with a control oligo. The 1628-injected mice did not produce higher numbers of P815-specific CD8 cells as measured by P1A-, and P1E-tetramer staining and Immunoscope analysis. Furthermore, tumor-specific CD8 cells in 1628 did not show enhanced antitumoral cytotoxicity when analyzing lymphocyte-tumor cell co-cultures or transcription of the cytotoxic CD8-cell associated molecules interferon gamma, FAS ligand, perforin, or granzyme B by quantitative real-time RT-PCR. These experiments show that there is no enhanced induction of an antitumoral CD8 response after in situ administration of poly-G-ODNs in the P815 mastocytoma model.

Immunostimulatory CpG-DNA activates murine microglia.

Bacterial DNA containing motifs of unmethylated CpG dinucleotides (CpG-DNA) triggers innate immune cells through the pattern recognition receptor Toll-like receptor 9 (TLR-9). CpG-DNA possesses potent immunostimulatory effects on macrophages, dendritic cells, and B lymphocytes. Therefore, CpG-DNA contributes to inflammation during the course of bacterial infections. In contrast to other TLR-dependent microbial patterns, CpG-DNA is a strong inductor of IL-12. Thus, it acts as a Th1-polarizing agent that can be utilized as potent vaccine adjuvant. To assess the role of CpG-DNA in immune reactions in the CNS, we analyzed the effects of CpG-DNA on microglial cells in vitro and in vivo. Primary microglial cells as well as microglial cell lines express TLR-9 mRNA. Consequently, CpG-DNA activated microglial cells in vitro and induced TNF-alpha, IL-12p40, IL-12p70, and NO. Furthermore, MHC class II, B7-1, B7-2, and CD40 molecules were up-regulated. In addition, phagocytic activity of microglia was enhanced. After intracerebroventricular injection of CpG-DNA, microglial cells were activated and produced TNF-alpha and IL-12p40 transcripts, as shown by in situ hybridization. These results indicate that microglia is sensitive to CpG-DNA. Thus, bacterial DNA containing CpG motifs could not only play an important role during infections of the CNS, but also might trigger and sustain Th1-dominated immunopathogenic reactions.

Oligonucleotides tethered to a short polyguanylic acid stretch are targeted to macrophages: enhanced antiviral activity of a vesicular stomatitis virus-specific antisense oligonucleotide.

The poor membrane permeability of oligonucleotides is one of the major problems of antisense technology. Here we report the construction of designer oligonucleotides for targeted delivery to macrophages. The oligonucleotides tethered to a 10-mer poly(G) sequence at their 3' ends were recognized by scavenger receptors on macrophages and were taken up about 8- to 10-fold as efficiently as those oligonucleotides that either lacked a poly(G) tail or that contained a 10-mer poly(C) tail instead of the poly(G) tail. The enhanced uptake of poly(G) constructs was inhibited in the presence of poly(G) and other known ligands of the scavenger receptor. The bioefficacy of poly(G)-mediated targeting of antisense oligonucleotides (ANS) was demonstrated by using vesicular stomatitis virus (VSV) as a model system. The ability of ANS directed against the translation initiation site of N protein mRNA of VSV to inhibit virus replication was assessed. The ANS with the 10-mer poly(G) sequences (ANS-G) brought about significant inhibition of VSV replication in J774E cells (a murine monocyte/macrophage cell line) and Chinese hamster ovary (CHO) cell transfectants expressing scavenger receptors. The ANS lacking a 10-mer poly(G) stretch were ineffective. The inhibition of VSV replication due to ANS-G was completely abrogated in the presence of 10-mer poly(G), indicating that the antisense effect of the ANS-G molecule was a consequence of scavenger receptor-mediated enhanced uptake. Importantly, antisense molecules linked exclusively by natural phosphodiester bonds were as bioeffective as those synthesized with a mixed backbone of phosphodiester and phosphorothioate. Taken together, these results suggest that macrophage-directed designer ANS against infective agents may simply be obtained by adding a short stretch of guanylic acid sequence to the desired specific ANS during solid-phase synthesis. This nucleic acid-based strategy, which utilizes homogeneous preparation of ANS, may find applications in directed manipulation of macrophage metabolism for a variety of purposes as well as in therapy of a broad spectrum of macrophage-related disorders amenable to the antisense approach.

Template-dependent biosynthesis of poly(G) x poly (C) and its antiviral activity in vitro and in vivo.

Experimental conditions for poly(G) synthesis from GTP on a poly(C) template with the aid of Escherichia coli DNA-dependent RNA polymerase were investigated. The reaction product was purified without the use of RNase. On the basis of spectral data, gel permeation chromatography, affinity adsorption and electron microscopic visualization, the poly(G) x poly(C) product was assumed to possess a high degree of structural regularity. Its in vitro and in vivo antiviral activities were compared with those of traditional poly(G) x poly(C) and poly(I) x poly(C). Template-dependent poly(G) x poly(C) was similar in its in vitro activity to poly(I) x poly(C) or even surpassed it, whereas the 'traditional' poly(G) x poly(C) was only slightly active in vitro. However, 'traditional' poly(G) x poly(C) and poly(I) x poly(C) had similar activity in vivo, whereas template-dependent poly(G) x poly(C) was much less active in vivo. The role of intramolecular structural regularity in the in vitro and in vivo antiviral activity of polyribonucleotide duplexes is discussed.

The helicase activity associated with hepatitis C virus nonstructural protein 3 (NS3).

To assess the RNA helicase activity of hepatitis C virus (HCV) nonstructural protein 3 (NS3), a polypeptide encompassing amino acids 1175 to 1657, which cover only the putative helicase domain, was expressed in Escherichia coli by a pET expression vector. The protein was purified to near homogeneity and assayed for RNA helicase activity in vitro with double-stranded RNA substrates prepared from a multiple cloning sequence and an HCV 5' nontranslated region (5'-NTR) or 3'-NTR. The enzyme acted successfully on substrates containing both 5' and 3' single-stranded regions (standard) or on substrates containing only the 3' single-stranded regions (3'/3') but failed to act on substrates containing only the 5' single-stranded regions (5'/5') or on substrates lacking the single-stranded regions (blunt). These results thus suggest 3' to 5' directionality for HCV RNA helicase activity. However, a 5'/5' substrate derived from the HCV 5'-NTR was also partially unwound by the enzyme, possibly because of unique properties inherent in the 5' single-stranded regions. Gel mobility shift analyses demonstrated that the HCV NS3 helicase could bind to either 5'- or 3'-tailed substrates but not to substrates lacking a single-stranded region, indicating that the polarity of the RNA strand to which the helicase bound was a more important enzymatic activity determinant. In addition to double-stranded RNA substrates, HCV NS3 helicase activity could displace both RNA and DNA oligonucleotides on a DNA template, suggesting that HCV NS3 too was disposed to DNA helicase activity. This study also demonstrated that RNA helicase activity was dramatically inhibited by the single-stranded polynucleotides. Taken altogether, our results indicate that the HCV NS3 helicase is unique among the RNA helicases characterized so far.

Influence of lipoteichoic acid structure on recognition by the macrophage scavenger receptor.

Lipoteichoic acids (LTAs) belong to the immunostimulatory class of molecules of gram-positive bacteria (GPB). Previous investigations showed that the macrophage scavenger receptor (SR), a glycosylated trimeric transmembrane protein, binds directly to many GPB, possibly via LTA. SR binding to other ligands is dependent upon the spatial characteristics of the repeating negative charge of the ligand. We therefore investigated SR recognition of LTA species with various charge densities and distributions by determining the capacity of these LTAs to compete with the binding of metabolically labeled SR to beads coated with the known SR ligand polyguanylic acid. Staphylococcus aureus LTA, a classical LTA type (unbranched 1,3-linked polyglycerophosphate chain covalently bound to a membrane diacylglyceroglycolipid), had a 50% inhibitory concentration (IC50) for inhibition of SR binding of 0.84 microg/ml. When the S. aureus LTA was rendered more negatively charged by removal of ester-linked alanine from the polyglycerophosphate backbone, the IC50 dropped to 0.23 microg/ml. Other polyglycerophosphate LTAs from Enterococcus faecalis, Enterococcus faecium, Enterococcus hirae, Listeria monocytogenes, Listeria welshimeri, and Streptococcus sanguis showed IC50S of 0.5 to 2.1 microg/ml, supporting the role of negative charge in binding to SR. Accordingly, the zwitterionic LTA of Streptococcus pneumoniae and Clostridium innocuum LTA substituted with positively charged sugar residues had no binding capacity. Monoglycerophosphate branches, but not succinyl ester, affected binding of lipoglycans. The data presented above parallel the previous findings for whole organisms and support the role of surface-associated LTA as a major ligand of GPB for binding to SR. Whether binding of LTA and whole GPB to macrophages initiates uptake and degradation or results in signal transduction remains to be determined.

Effects of streptolysin O, polyriboinosinic-polyribocytidylic acid and combinations with cyclophosphamide on the hepatic arylamine N-acetyltransferase and cytochrome P450-dependent monooxygenases in rats.

There is evidence that immunostimulation depresses the function of various cytochrome P450 (CYP)-dependent monooxygenases but activates the arylamine N-acetyltransferase (NAT). Therefore, the effects of the synthetic immunostimulator polyriboinosinic-polyribocytidylic acid (plC, 8 mg/kg i.p.), of sublytic doses of the streptococcal toxin streptolysin O (SLO, 50 HU/kg i.v. for 5 d) and of the immunosuppressor cyclophosphamide (CP, 100 mg/kg i.p.) on NAT and some monooxygenases were studied in rat liver. It was also evaluated whether CP might antagonize the effects of plC and SLO on drug metabolism. SLO, plC and CP reduced CYP content and the activities of some monooxygenases. NAT was significantly inhibited by CP (given 5 d before sacrifice) but not by plC, SLO or CP when given 2 d before sacrifice. CP lacked any effect on NAT if it was administered prior to SLO. However, it deteriorated synergistically the inhibition of the monooxygenases caused by SLO and plC.

[Effects of interferon inducers on chemically-induced mutagenesis and carcinogenesis]. / Vliianie induktorov interferona na khimicheski indutsirovannyi mutagenez i kantserogenez.

The murine bone marrow cellular chromosomal aberration technique was used to reveal anticlastogenic effects of the natural interferon inductors ridostin and larifan, as well as the synthetic ones polyguacil and amyxin. The action of the interferon inductors was timed to the maximum production of interferon in the body. Anticarcinogenic, antitumor, and antimetastatic properties of the above interferon inductors were found by using classical experimental models of carcinogenesis. Some mechanisms of antimutagenic and coupled anticarcinogenic action of interferon inductors were considered. The natural interferon inductor larifan was found to have an antipromoter activity. The treatment regimen by using interferon inductors in combination with the immunomodulator thymosin, a thymic hormone, was under discussion.

Circumvention of multidrug resistance in neoplastic cells through scavenger receptor mediated drug delivery.

A conjugate of the antineoplastic drug daunomycin (DNM) with maleylated bovine serum albumin (MBSA-DNM) was taken up with high efficiency by a multidrug resistant variant, JD100, of the murine-macrophage tumour cell line, J774A.1, through the scavenger receptors resulting in cessation of DNA synthesis. In contrast, free DNM at similar concentrations did not affect the incorporation of [3H]thymidine by these cells. These results suggest that receptor-mediated intracellular delivery of antineoplastic drugs could be a viable and new approach for overcoming the problem of multidrug resistance in chemotherapy of neoplastic diseases.

[Biological activity of the poly(G).poly(C) complex, modified by divalent platinum compounds]. / Biologicheskaia aktivnost' kompleksa poli(G).poli(C), modifitsirovannogo soedinenimi dvukhvalentnoi platiny.

Modification of poly(G).poly(C) with cys-diaminodichloroplatinum (cys-DDP) at the level of rb = 0.02 increased the in vivo antiviral and interferon-inducing activity of the complex, in contrast to the data reported for complex poly(G).poly(C). Antiinfluenza activity in this case depends on the method of modification and increases more intensively when a ready complex is treated with cys-DDP, as against treatment of poly(G) alone before the formation of a complex with poly(C). If rb is increased, the activity reduces again. Modification with trans-DDP at rb = 0.02 also leads to an increase of antiinfluenza activity of poly(G).poly(C), but mainly after pretreatment of poly(G).