Interaction of the UvrABC nuclease system with a DNA duplex containing a single stereoisomer of dG-(+)- or dG-(-)-anti-BPDE

Oligonucleotides containing site-specifically-modified N2-guanine (+)-trans-, (-)-trans-, (+)-cis-, and (-)-cis-BPDE adducts were ligated into 50-base-pair DNA fragments. These substrates were used in reactions with the Escherichia coli UvrABC nuclease system. The interaction of the UvrA2 and UvrA2B complexes with these four stereoisomers was probed using DNase I footprinting and gel mobility shift assays. DNase I digestion of substrates containing each stereoisomer of BPDE displayed a unique pattern which was consistent with the known structure of these DNA adducts. UvrA and UvrA2B appeared to interact very similarly with all four substrates. Binding of UvrA2 to these substrates produced a 33-bp footprint, and the UvrB--DNA complex resulted in footprint of 24 bp. The UvrABC nuclease system produced bimodal incisions at the eighth phosphate 5' and the fifth, sixth, or seventh phosphate 3' to the modified guanine. The variation of the 3' incision site was linked to the stereochemistry and orientation of the BPDE adduct. For example, the 3' incision of the 50-bp duplex containing (-)-trans-BPDE-N2-guanine was inhibited at the fifth phosphate. UvrABC nuclease incision kinetics revealed a hierarchy of specificity. The intercalative cis isomers were incised more efficiently than the corresponding trans isomers which lie in the minor groove. The (+) enantiomers were incised more efficiently than the (-) form for both cis and trans isomers. These observations reveal that UvrABC nuclease recognition and incision are directly influenced by the conformation of the DNA adduct.

Nd: YAG laser lysis of the fibrinous membrane and remnant substance on the anterior surface of intraocular lens

PURPOSE

To determine the effects of Nd: YAG laser to disrupt the fibrinous membrane and remnant substance on the anterior surface of intraocular lens.

METHODS

Nd: YAG laser was applied on 23 cases of fibrinous membrane formation and 8 cases of remnant substance on the anterior surface of intraocular lenses (IOL) which had not responded well to steroid therapy. Eighteen cases were male and 13 female. The mean age was 49.7 years (range, 5 approximately 78 years). The interval between IOL implantation and laser therapy was 0.5 approximately 30 months in the fibrinous membrane cases and 3 approximately 10 days in the remnant substance cases. The energy applied was 0.8 approximately 3.0 mJ/exp. with 2 approximately 112 exposures. Mean follow-up period was 3.6 months.

RESULTS

Complications during therapy included only 2 cases of slight iris bleeding. Visual acuity after therapy was improved 1 line in 16 cases, 2 lines in 11 cases, 3 lines in 1 case, 4 lines in 1 case and 5 lines in 2 cases. No post-therapy complication was found.

CONCLUSIONS

Nd: YAG laser lysis is an effective alternative to remove the fibrinous membrane and remnant substances on the anterior surface of IOL.

Primary posterior chamber intraocular lens implantation in traumatic cataract with posterior capsule breaks

BACKGROUND

In patients with incomplete posterior capsule support, posterior chamber intraocular lenses (PC-IOLs) were implanted with both haptics transscleral fixation. This causes more damage to the eye and may result in more complications. In patients with small posterior breaks, non-fixation or single haptic fixation may be adequate.

METHODS

Thirty-two consecutive patients of traumatic cataract with posterior capsule breaks caused by penetrating eye trauma were retrospected. Posterior chamber intraocular lenses were implanted in all these patients with three techniques, ie, without fixation, with single haptic fixation and with both haptics fixation. The selection of the technique was based on the position and size of the posterior capsule. The follow-up period was 21 days to 28 months (mean, 15.2 months).

RESULTS

Intra-operative problems included ciliary body bleeding (two patients, 6.25%) and enlargement of posterior capsule breaks (2 patients, 6.25%). Postoperative visual acuity was 0.5 or better (corrected) in 28 case (87.5%) and 0.1-0.4 in four patients (12.5%). Postoperative complications included hyphema (6 eyes, 18.8%), transient intraocular pressure elevation (6 eyes, 18.8%), transient hypotention (7 eyes, 21.8%). Postoperative IOL position were good except one case of IOL tilt. No pupillary capture or endophthalmitis was found.

CONCLUSIONS

Not all PC-IOLs have to be fixed by two haptics. In patients with small posterior capsule breaks, PC-IOL may not be fixed or fixed by only one haptics.

Angiotensin II partly mediates mechanical stress-induced cardiac hypertrophy

We have previously shown that mechanical stress induces activation of protein kinases and increases in specific gene expression and protein synthesis in cardiac myocytes, all of which are similar to those evoked by humoral factors such as growth factors and hormones. Many lines of evidence have suggested that angiotensin II (Ang II) plays a vital role in cardiac hypertrophy, and it has been reported that secretion of Ang II from cultured cardiac myocytes was induced by mechanical stretch. To examine the role of Ang II in mechanical stress-induced cardiac hypertrophy, we stretched neonatal rat cardiac myocytes in the absence or presence of the Ang II receptor antagonists saralasin (an antagonist of both type 1 and type 2 receptors), CV-11974 (a type 1 receptor-specific antagonist), and PD123319 (a type 2 receptor-specific antagonist). Stretching cardiac myocytes by 20% using deformable silicone dishes rapidly increased the activities of mitogen-activated protein (MAP) kinase kinase activators and MAP kinases. Both saralasin and CV-11974 partially inhibited the stretch-induced increases in the activities of both kinases, whereas PD123319 showed no inhibitory effects. Stretching cardiac myocytes increased amino acid incorporation, which was also inhibited by approximately 70% with the pretreatment by saralasin or CV-11974. When the culture medium conditioned by stretching cardiocytes was transferred to nonstretched cardiac myocytes, the increase in MAP kinase activity was observed, and this increase was completely suppressed by saralasin or CV-11974. These results suggest that Ang II plays an important role in mechanical stress-induced cardiac hypertrophy and that there are also other (possibly nonsecretory) factors to induce hypertrophic responses.

Mechanical stress activates protein kinase cascade of phosphorylation in neonatal rat cardiac myocytes

We have previously shown that stretching cardiac myocytes evokes activation of protein kinase C (PKC), mitogen-activated protein kinases (MAPKs), and 90-kD ribosomal S6 kinase (p90rsk). To clarify the signal transduction pathways from external mechanical stress to nuclear gene expression in stretch-induced cardiac hypertrophy, we have elucidated protein kinase cascade of phosphorylation by examining the time course of activation of MAP kinase kinase kinases (MAPKKKs), MAP kinase kinase (MAPKK), MAPKs, and p90rsk in neonatal rat cardiac myocytes. Mechanical stretch transiently increased the activity of MAPKKKs. An increase in MAPKKKs activity was first detected at 1 min and maximal activation was observed at 2 min after stretch. The activity of MAPKK was increased by stretch from 1-2 min, with a peak at 5 min after stretch. In addition, MAPKs and p90rsk were maximally activated at 8 min and at 10 approximately 30 min after stretch, respectively. Raf-1 kinase (Raf-1) and (MAPK/extracellular signal-regulated kinase) kinase kinase (MEKK), both of which have MAPKKK activity, were also activated by stretching cardiac myocytes for 2 min. The angiotensin II receptor antagonist partially suppressed activation of Raf-1 and MAPKs by stretch. The stretch-induced hypertrophic responses such as activation of Raf-1 and MAPKs and an increase in amino acid uptake was partially dependent on PKC, while a PKC inhibitor completely abolished MAPK activation by angiotensin II. These results suggest that mechanical stress activates the protein kinase cascade of phosphorylation in cardiac myocytes in the order of Raf-1 and MEKK, MAPKK, MAPKs and p90rsk, and that angiotensin II, which may be secreted from stretched myocytes, may be partly involved in stretch-induced hypertrophic responses by activating PKC.

Comparison of four methods to generate immunoreactive fragments of a murine monoclonal antibody OC859 against human ovarian epithelial cancer antigen

In the present study, four different proteases (pepsin, papain, bromelain and ficin) were screened with a murine monoclonal antibody OC859, in order to verify whether different digestion procedures could improve yield and stability of the F(ab')2 or Fab fragments. The yields of F(ab')2 or Fab fragments from digestion with pepsin, papain, bromelain and ficin were respectively 20.3 +/- 2.0%, 50.5 +/- 5.0%, 74.4 +/- 2.7% and 82.8 +/- 10.2% of the theoretical maximum. Immunoreactivity in a noncompetitive solid-phase radioimmunoassay (SPRIA) of the fragments generated by the four proteases were respectively 10 +/- 5%, 36 +/- 5%, 60 +/- 6% and 75 +/- 6% of the intact OC859 IgG. These results suggested that the fragmentation of OC859 with ficin gave a higher yield of superior immunoreactive fragments.

EFIA/YB-1 is a component of cardiac HF-1A binding activity and positively regulates transcription of the myosin light-chain 2v gene

Transient assays in cultured ventricular muscle cells and studies in transgenic mice have identified two adjacent regulatory elements (HF-1a and HF-1b/MEF-2) as required to maintain ventricular chamber-specific expression of the myosin light-chain 2v (MLC-2v) gene. A rat neonatal heart cDNA library was screened with an HF-1a binding site, resulting in the isolation of EFIA, the rat homolog of human YB-1. Purified recombinant EFIA/YB-1 protein binds to the HF-1a site in a sequence-specific manner and contacts a subset of the HF-1a contact points made by the cardiac nuclear factor(s). The HF-1a sequence contains AGTGG, which is highly homologous to the inverted CCAAT core of the EFIA/YB-1 binding sites and is found to be essential for binding of the recombinant EFIA/YB-1. Antiserum against Xenopus YB-3 (100% identical in the DNA binding domain and 89% identical in overall amino acid sequence to rat EFIA) can specifically abolish a component of the endogenous HF-1a complex in the rat cardiac myocyte nuclear extracts. In cotransfection assays, EFIA/YB-1 increased 250-bp MLC-2v promoter activity by 3.4-fold specifically in the cardiac cell context and in an HF-1a site-dependent manner. EFIA/YB-1 complexes with an unknown protein in cardiac myocyte nuclear extracts to form the endogenous HF-1a binding activity. Immunocoprecipitation revealed that EFIA/YB-1 has a major associated protein of approximately 30 kDa (p30) in cardiac muscle cells. This study suggests that EFIA/YB-1, together with the partner p30, binds to the HF-1a site and, in conjunction with HF-1b/MEF-2, mediates ventricular chamber-specific expression of the MLC-2v gene.

Effect of vesicle size and lipid composition on the in vivo tumor selectivity and toxicity of the non-cross-resistant anthracycline annamycin incorporated in liposomes

Annamycin (Ann) is a non-cross-resistant lipophilic anthracycline antiobiotic optimally suited for liposome delivery. We studied how vesicle size and presence of phospholipids with a high phase transition temperature and monosialoganglioside (GM I) in the liposome bilayers affect the pharmacokinetics, tumor selectivity and toxicity of Ann. Entrapment of Ann in multilamellar vesicles (L-Ann) resulted in a 20% lower heart AUC and a 30-40% higher tumor and liver AUC. Reduction of the liposome size from 1.6 to 0.03 microns increased Ann plasma circulation time and tumor AUC by 2-fold, enhanced Ann tumor selectivity and decreased Ann subacute toxicity by 2-fold. The presence of phospholipids with a high phase transition temperature and GMI in the liposome bilayers further prolonged Ann plasma circulation time by 2- to 4-fold, did not increase Ann tumor AUC and moderately increased Ann subacute toxicity. The anti-tumor activity of Ann correlated with the tumor AUC achieved with each particular formulation. Our results strongly suggest that vesicle size may be an important determinant of the therapeutic index of liposomal Ann, but they fail to demonstrate a beneficial tumor-targeting effect of liposomes composed of GMI and phospholipids with a high phase transition temperature, as has been reported for the hydrophilic parent compound doxorubicin.

Cyanide inhibition of porcine kidney diamine oxidase and bovine plasma amine oxidase: evidence for multiple interaction sites

The interactions of cyanide and phenylhydrazine with porcine kidney diamine oxidase (PKDAO) and bovine plasma amine oxidase (BPAO) (EC 1.4.3.6) have been investigated. Cyanide displays mixed noncompetitive inhibition against amine substrates and also against O2. EPR spectroscopy shows that cyanide binds to an equatorial site on Cu(II) and can be displaced by chloride, which is not an inhibitor, without recovery of activity, indicating that Cu(II)-bound cyanide is not inhibitory. 14CN-. studies have shown that one cyanide in PKDAO and two in BPAO are covalently and irreversibly bound per enzyme dimer at an unknown site, even under conditions where cyanide is not bound to Cu(II). These cyanides have no effect on activity or on binding of phenylhydrazine to the enzymes. Cyanide also binds reversibly to the organic cofactor in both enzymes, presumably as a cyanohydrin, leading to the observed mixed noncompetitive inhibition against substrate. In both enzymes, two phenylhydrazines react per enzyme dimer. The kinetics of phenylhydrazine titration are affected by cyanide, which indicates that phenylhydrazine and cyanide react at the same carbonyl group in the enzymes. The results suggest that inhibition of amine oxidases by cyanide is through a carbonyl reagent and a Cu(I) ligand rather than through a Cu(II) ligand.

Partial circumvention of multi-drug resistance by annamycin is associated with comparable inhibition of DNA synthesis in the nuclear matrix of sensitive and resistant cells

We studied the subcellular and subnuclear distributions of the partially cross-resistant anthracycline Annamycin (Ann) in KB-3-1 and multi-drug resistant KB-VI cells. Subcellular drug localization was assessed qualitatively by fluorescence microscopy and quantitatively by cell fractionation and fluorescence measurements. Doxorubicin (Dox) localized predominantly in the nucleus in KB-3-1 cells and in the membranes in KB-VI cells. In contrast, the subcellular distribution of Ann was identical in both cell lines, with preferential drug localization in the perinuclear region, Golgi apparatus, endoplasmic reticulum and endosomes. Dox rate of efflux from the nucleus was negligible in KB-3-1 cells but markedly enhanced in KB-VI cells, whereas Ann was lost at a similar rate from the nucleus in both cell lines. In KB-3-1 cells Dox levels in the nuclear non-matrix were about 2-fold higher than those of Ann, while in the matrix the inverse relationship was observed. In spite of these differences, Dox and Ann had a similar inhibitory effect on new DNA synthesis in the nuclear matrix and non-matrix of KB-3-1 cells. Dox levels were reduced by 10-fold in the nuclear non-matrix and 2-fold in the matrix in KB-VI cells compared with KB-3-1 cells, whereas Ann levels were reduced by about 2- to 3-fold in the non-matrix and were unchanged in the matrix. In correlation with these findings, Dox did not cause inhibition of new DNA synthesis in either nuclear fraction in KB-VI cells, whereas inhibition of new DNA synthesis in the matrix by Ann was similar in both cell lines. Our results indicate that Ann's partial circumvention of multi-drug resistance is associated with its ability to cause comparable new DNA synthesis inhibition in the nuclear matrix of sensitive and resistant cells.

Sequence specificity of DNA-DNA interstrand cross-link formation by cisplatin and dinuclear platinum complexes

The sequence specificity of interstrand cross-links induced in DNA by mononuclear and dinuclear platinum complexes in a 49-base-pair DNA duplex has been determined directly. This new assay takes advantage of the fact that 3'-->5' exonuclease digestion of randomly platinated DNA produces a pool of fragments of different lengths. This treatment allows identification of the spectrum of adducts impeding the exonuclease scission. Interstrand cross-linked adducts produce fragments that may remain complementary in the proximity of the binding site. As a result, these fragments may act as primer templates for extension upon subsequent treatment with a DNA polymerase. This extension increases the size of the oligonucleotide fragments, which may be evidenced by a more slowly migrating band on a sequencing gel. Concomitantly, the original band corresponding to the digested cross-link decreases in intensity. Therefore, comparison of a sequencing gel after digestion only and after the "digestion-extension" treatment should show the disappearance, or diminished band intensity, of only those fragments with interstrand cross-links. This approach was applied to the analysis of DNA interstrand cross-links formed by cis-[PtCl2(NH3)2] (cis-DDP) and [(trans-PtCl(NH3)2)2H2N(CH2)4NH2]Cl2. Cis-DDP was confirmed to form interstrand cross-links at d(GC) sequences but, interestingly, interstrand cross-links predominated in a sequence GCGG, with possible 1,3-intrastrand but no 1,2-intrastrand cross-links forming. The dinuclear compound formed 1,2, 1,3, and 1,4 DNA interstrand cross-links between guanines on opposite strands. In 1,3 and 1,4 cross-links, the guanines are separated by one and two base pairs, respectively, whereas a 1,2 cross-link is formed from guanines on neighboring base pairs.(ABSTRACT TRUNCATED AT 250 WORDS)

Antitumor activity of free and liposome-entrapped annamycin, a lipophilic anthracycline antibiotic with non-cross-resistance properties

The lipophilic anthracycline antibiotic annamycin (Ann) was entrapped in liposomes of different size [median diameter: 1.64 microns, multilamellar liposomal Ann (L-Ann); 0.030 micron, small unilamellar Ann (S-Ann)] with > 90% entrapment efficiency and tested in vitro against four pairs of sensitive and multidrug-resistant (MDR) tumor cell lines and in vivo by the i.v. route in five tumor models: advanced s.c. B16 melanoma; s.c. M5076 reticulosarcoma; lung metastases of Lewis lung carcinoma; and s.c. KB and KB-V1 xenografts in nude mice. Predetermined optimal doses of the different formulations were used and the results were compared with doxorubicin (Dox). In vitro, Ann, either in suspension in 10% dimethyl sulfoxide (F-Ann) (1 mg/ml) or entrapped in liposomes, was able to partially overcome resistance in all four pairs of sensitive and MDR KB, 8226, P388, and CEM cell lines (resistance indexes 63, 269, 333, and 356 for Dox versus 4, 5, 19, and 8.7 for L-Ann, respectively). In vivo, both F-Ann and liposome-entrapped Ann were slightly more effective than Dox in inhibiting the growth of advanced s.c. B16 melanoma tumors. L-Ann was markedly more effective than Dox and moderately more effective than F-Ann in prolonging the life span of animals bearing s.c. M5076 and lung metastases of Lewis lung carcinoma tumors. All drugs were equally effective at optimal doses in delaying the growth of s.c. KB xenografts, whereas all Ann formulations were markedly more effective than Dox in delaying the growth of s.c. KB-V1 (MDR) xenografts. In all in vivo experiments, S-Ann was consistently more effective than L-Ann and L-Ann was more effective than F-Ann. These results indicate that (a) Ann is more effective than Dox by the i.v. route against several tumor models and that MDR tumors are partially not cross-resistant to Ann both in vitro and in vivo, (b) liposomes enhance the in vivo antitumor properties of Ann, and (c) small liposomes are more effective than large liposomes in enhancing Ann antitumor activity.

Cellular pharmacology of the partially non-cross-resistant anthracycline annamycin entrapped in liposomes in KB and KB-V1 cells

The in vitro cytotoxicity, cellular pharmacology, and DNA lesions induced by the lipophilic anthracycline annamycin (Ann) were studied in KB and KB-V1 (multidrug-resistant) cells. Ann was tested in suspension in saline and 10% dimethylsulfoxide (DMSO: final concentration, 0.05%-0.5%) or entrapped in multilamellar liposomes (median size, 1.57 microns). Doxorubicin (Dox) was about twice as cytotoxic as Ann or liposome-entrapped Ann (L-Ann) against KB cells. Both Ann and L-Ann displayed a partial lack of cross-resistance with Dox (resistance indices: > 60 for Dox, 4.7 for Ann, 4.0 for L-Ann). Accumulation of Ann in KB and KB-V1 cells was consistently about 2-3 and 10-20 times higher, respectively, than that of Dox. Cellular retention of Ann in KB and KB-V1 cells was about 2 and 30 times higher, respectively, than that of Dox as a result of the different efflux patterns of the two drugs: Dox was not effluxed from KB cells but was significantly effluxed from KB-V1 cells (66% at 1 h, whereas Ann efflux was similar in both cell lines (about 50% at 1 h). Dox retention in KB-V1 cells was increased by a factor of 2 in the presence of verapamil or cyclosporine A, but Ann retention was not. In addition, accumulation of Dox in KB-V1 cells was enhanced by the metabolic inhibitor deoxyglucose/azide and the membrane carboxylic ionophore monensin, whereas accumulation of Ann was not affected by either agent. All these findings indicate significant differences in the cellular transmembrane transport systems between Dox and Ann and suggest that Ann efflux is not mediated by P-glycoprotein. Liposome entrapment reduced by a factor of 1.3-2.0 the cellular accumulation of Ann without affecting its cytotoxicity. As compared with Dox, both Ann and L-Ann induced 3 times more DNA double- and single-strand breaks in KB cells. In KB-V1 cells, Dox did not induce DNA damage, whereas the extent of DNA breaks induced by both Ann and L-Ann was similar to that induced by Dox in KB cells. Our results indicate (1) that the lack of cross-resistance between Ann and Dox is associated with a markedly enhanced accumulation and retention of Ann in KB-V1 cells and (2) that the type of liposomes used does not significantly affect the cellular effects of Ann.