Medicinal Chemistry - Volume 2, Issue 3, 2006

Bisphosphonates are now well established as successful agents for the prevention and treatment of postmenopausal osteoporosis and corticosteroid-induced bone loss. Bisphosphonates have also recently become important in the management of cancer-induced bone disease, and they now have a widely recognized role for patients with multiple myeloma and bone metastases secondary to breast cancer and prostate cancer. Recent studies suggest that, besides the strong antiosteoclastic activity, the efficacy of such compounds in the oncological setting could also be due to direct antitumor effect. However, the effect of bisphosphonates to ovarian and endometrial cancers has not been elucidated. Thus, we examined the direct effect of bisphosphonates on the various ovarian cancer cell lines. Except for etidronate, all of bisphosphonates examined had the direct inhibitory effects on proliferation of all ovarian cancer cell lines used. Especially, pamidronate had the most marked inhibitory effect and inhibited dose-dependently the proliferation of ovarian cancer cell lines. KFr 13 cells among ovarian cancer cell lines used was the most sensitive to pamidronate and the caspase 3 activity was markedly stimulated by treatment with pamidronate, suggesting induction of apoptosis.

The aim of this study was to investigate cellular response to several ruthenium(III), chromium(III) and rhodium(III) compounds carrying bidentate β-diketonato ligands: [(acac)-acetylacetonate ligand, (tfac)- trifluoroacetylacetonate ligand]. Cell sensitivity studies were performed on several cell lines (A2780, cisplatin-sensitive and -resistant U2-OS and U2-OS/Pt, HeLa, B16) using growth-inhibition assay. Effect of intracellular GSH depletion on cell sensitivity to the agents was analyzed in A2780 cells. Flow cytometry was used to assess apoptosis by Annexin-VFITC/ PI staining, and to analyze induction of caspase-3 activity. Possible DNA binding/damaging affinity was investigated, by inductively coupled mass spectrometry, and by 14C-thymidine / 3H-uridine incorporation assay. Cell sensitivity studies showed that the pattern of sensitivity to Ru(tfac)3 complex of the two cisplatin-sensitive/-resistant osteosarcoma cell lines, U2-OS and U2-OS/Pt, was similar to that of A2780 cells (72 h exposure), with the IC50 being around 40μM. The growth-inhibitory effect of Ru(acac)3 ranged over 100μM, while Cr(III) and Rh(III) complexes were completely devoid of antitumor action in vitro. Ru(tfac)3 exhibited strong potential for apoptosis induction on A2780 cells (up to 40%) and caused cell cycle arrest in the S phase as well as decrease of the percent of G1 and G2 cells. Ru(acac)3- induced apoptosis was slightly higher than 10%, whereas activation of caspase-3 in HeLa cells was moderate. DNA binding study revealed that only Cr(acac)3 was capable of binding DNA, while Cr(III) and Ru(III) compounds possess potential to inhibit DNA/RNA synthesis. In conclusion, only Ru(III) complexes showed potential for antitumor action.

Sorbitol dehydrogenase (SDH) is the second enzyme in the polyol pathway of glucose metabolism and is a possible target for the treatment of the complications of diabetes. In this study the molecular modelling program DOCK was used to analyse 249,071 compounds from the National Cancer Institute Database and predict those with high affinity for SDH. From a total of 21 tested the 7 compounds including flavin adenine dinucleotide disodium hydrate, (+)- Amethopterin, 3-hydroxy-2-napthoic(2-hydroxybenzylidene) hydrazide, folic acid, N-2,4-dinitrophenyl-L-cysteic acid, Vanillin azine and 1H-indole-2,3-dione,5-bromo-6-nitro-1-(2,3,4-tri-O-acetyl-α-L-arabinopyranosyl)-(9Cl), were shown to inhibit SDH and displayed IC50 values of 0.192 μM, 1.1 μM, 1.2 μM, 4.5 μM, 5.3 μM, 7 μM and 28 μM, respectively. These compounds may aid the design of pharmaceutical agents for the treatment of diabetes complications.

A quantitative structure-activity relationship study has been conducted on two different series of acyclic hydroxamic acid analogs acting as matrix metalloproteinase (MMP) inhibitors. The results suggest that in a few cases, the hydrophobic property of the molecules is the major governing factor. However, in some cases, the polarizability of the molecules is shown to be dominant. The two enzymes, MMP-9 and MMP-13, are shown to behave in a similar fashion with any group of inhibitors.

Lipoxygenase plays an essential role in the biosynthesis of the leukotrienes. Leukotrienes, as LO metabolites of arachidonic acid (AA), have been implicated as mediators in the pathophysiology of inflammatory diseases, host defense reactions and to play important role in the propagation of the diseases states, exacerbating the local events and ultimately leading to tissue damage. Simple stable molecules containing the hydroxamic acid functionality have been shown to inhibit 5-lipoxygenase. In fact, several hydroxamates are orally active inhibitors of the enzyme as determined by their ability to block the biosynthesis of leukotriene in vivo. In order to establish the inhibitory utility of simple hydroxamates several ω-phenylalkyl and ω-naphthylalkyl hydroxamic acids were synthesized. In an attempt to expand and delineate these results we tried to synthesize some more for a further pharmacochemical study. Since lipophilicity is a significant physicochemical property determining distribution, bioavailability, metabolic activity and elimination, we tried to determine experimentally their lipophilicity from RPTLC method. The compounds are tested in vitro on: a) soybean lipoxygenase inhibition, b) interaction with 1,1-diphenyl-2- picryl-hydrazyl (DPPH) stable free radical, c) the HO. radical mediated oxidation of DMSO, d) inhibition of lipid peroxidation, e) scavenging of superoxide anion radicals f) interaction with glutathione and g) in vivo for the inhibition of carrageenin induced rat paw edema. The compounds have shown important antioxidant activity, medium anti-inflammatory activity and potent inhibition of soybean lipoxygenase as a result of their physichochemical features.

Angiotensin II (Ang II) elicits numerous inflammatory-proliferative responses in vascular cells, thereby being involved in atherosclerosis. We have previously shown that pigment epithelium-derived factor (PEDF) blocks the Ang IIinduced endothelial cell activation, thus suggesting that PEDF may play a role in atherosclerosis. However, effects of PEDF on T cell activation, another key steps of atherosclerosis, remain to be elucidated. In this study, we examined whether PEDF could inhibit the Ang II-induced MOLT-3 T cell proliferation in vitro and the way that it might achieve this effect. Ang II significantly stimulated DNA synthesis in MOLT-3 T cells, which was inhibited by PEDF, olmesartan, an Ang II type 1 receptor blocker, an anti-oxidant N-acetylcysteine (NAC), or antibodies directed against IL-2. PEDF or NAC suppressed gene expression of interleukin-2 (IL-2) in Ang II-exposed MOLT-3 T cells. Furthermore, PEDF blocked the Ang II-induced reactive oxygen species (ROS) generation and NADPH oxidase activity in MOLT-3 T cells. These results demonstrate that PEDF inhibits the Ang II-induced T cell proliferation by blocking autocrine production of IL-2 via suppression of NADPH oxidase-mediated ROS generation. Blockade by PEDF of T cell activation may become a novel therapeutic target for atherosclerosis.

Hemorrhagic shock followed by resuscitation (HSR) induces oxidative stress that leads to acute lung injury. Heme oxygenase-1 (HO-1), the rate-limiting enzyme in heme catabolism, is induced by oxidative stress and is thought to play an important role in the protection from oxidative tissue injuries. We previously demonstrated that HO-1 induction by heme arginate (HA), a strong inducer of HO-1, ameliorated HSR-induced lung injury and inflammation. Cellular redox state is known to modulate the DNA biding activity of the transcription factors; nuclear factor-κB (NF-κB) and activator protein-1 (AP-1). In the present study, we treated rats with HA (30 mg/kg of hemin) 18 h prior to HSR and examined its effect on the DNA binding activity of NF-κB and AP-1 at 1.5 h after HSR. HSR significantly increased the DNA binding activity of NF-κB as well as AP-1, while HA pretreatment markedly attenuated the activities of these transcription factors. In contrast, administration of tin mesoporphyrin, a specific competitive inhibitor of HO activity, to HA-pretreated animals abolished the suppressive effect of HA on the activities of NF-κB and AP-1, and increased these activities to almost the same level as those in HSR animals. Our findings indicate that HA pretreatment can significantly suppress the increased activity of NF-κB and AP-1 induced by HSR by virtue of its ability to induce HO-1. Our findings also suggest that HO-1 induced by HA pretreatment ameliorates HSR-induced lung injury at least in part mediated through the suppression of the activities of these transcription factors.

The phytochemical resveratrol has been reported to induce NQO1, an enzyme involved in detoxification reactions, by as yet undetermined mechanisms. Using K562 cells as a model, we showed that 25-50 μM resveratrol increased NQO1 that peaked at 24-48 h. A 2.5-fold rise in NQO1 protein levels was accompanied by a comparable elevation in mRNA copy number and a 3- to 5-fold increase in NQO1 enzymatic activity. Fluorescent microscopic analysis in combination with transfection experiments with plasmids harboring different segments of the 5'-flanking region of NQO1 gene linked to a reporter provided evidence that the modulation of NQO1 gene expression by resveratrol involved the antioxidant response element ARE, accompanied by an increase in the state of phosphorylation of transcription factor Nrf2 and its re-distribution to the nucleus. This change in cellular localization of Nrf2 may be linked to resveratrol-elicited disruption of the Nrf2-Keap1 complex in the cytosol, followed by the translocation of Nrf2 to the nucleus where it locates the ARE-containing 5'-promoter region of NQO1 leading to its transcriptional activation.

M. tuberculosis, M. bovis and M. avium infections cause the most important mycobacterioses leading to increased mortality in patients with AIDS. Various 5-substituted 2'-deoxyuridines, arabinouridines, arabinocytidines and 2'-arabinofluoro-2'-deoxyuridines were synthesized and evaluated for their in vitro inhibitory activity against M. bovis, M. tuberculosis and M. avium. 5-(C-1 Substituted)-2'-deoxyuridine derivatives emerged as potent inhibitors of M. avium (MIC50 = 1-10 μg/mL range); 5-(1-azidovinyl)-2'-deoxyuridine being the most active (MIC50 = 1-5 μg/mL range). The nature of C-5 substituents appeared to be a determinant of anti-mycobacterial activity.

Two novel RGDF mimetics were synthesized with the use of 4-(1,2,3,4-tetrahydro-isoquinoline-7-yl)amino-4- oxo-butyric acid as a new surrogate of Arg-Gly motif. The synthesized compounds have demonstrated a high potency to inhibit platelet aggregation in vitro and to block FITC-Fg binding to αIIbβ3 on washed human platelets.

This study evaluated and compared the effect of insulin treatment on the status of brain, heart and kidney mitochondria isolated from 12-week streptozotocin (STZ)-induced diabetic rats versus STZ-diabetic animals treated with insulin during a period of 4 weeks. Mitochondria isolated from 12-week citrate (vehicle)-treated rats were used as control. Several mitochondrial parameters were evaluated: respiratory indexes (state 3 and 4 of respiration, respiratory control and ADP/O ratios), transmembrane potential, depolarization and repolarization levels, ATP, glutathione and coenzyme Q contents, production of hydrogen peroxide, superoxide dismutase, glutathione peroxidase and glutathione reductase activities and the ability of mitochondria to accumulate calcium. We observed that diabetes promoted a significant decrease in kidney and brain mitochondrial coenzyme Q9 content while this parameter was increased in heart mitochondria. Furthermore, diabetes induced a significant increase in hydrogen peroxide production in kidney mitochondria this effect being accompanied by a significant increase in glutathione peroxidase and reductase activities. Furthermore, brain mitochondria isolated from diabetic animals presented a lower ATP content and ability to accumulate calcium. In contrast, heart and kidney mitochondria presented a slight higher capacity to accumulate calcium. Insulin treatment normalized the levels of coenzyme Q9 and glutathione peroxidase and reductase activities and increased ATP content and the ability to accumulate calcium. Altogether these results suggest that insulin treatment attenuates diabetesinduced mitochondrial alterations protecting against the increase in oxidative stress and improving oxidative phosphorylation efficiency. In this line, insulin therapy, besides its well-known importance in the maintenance of glycemic control, may help to protect against mitochondrial dysfunction associated to several age-related disorders such as diabetes.

Flexible alignment and docking studies were conducted for the three octapeptides, ATLQANEV, AVLQSGFR, and ATLQAIAS, that were cleavable by SARS-CoV Mpro. It has been observed that all pharmacophores of the three peptides overlap very well, and that ATLQANEV binds best with the receptor, followed by AVLQSGFR, and then ATLQAIAS. During the process of docking the octapeptides to the SARS enzyme, the residues of the catalytic dyad, i.e., His-41 and Cys-145 are actively involved in forming the hydrogen bonds, so is the center residue (Gln) of all the three octapeptides. The findings are fully consistent with experimental observations. The present studies suggest that the octapeptides ATLQANEV and ATLQAIAS, like AVLQSGFR, might also be the good starting points for designing potential drugs against SARS.

Increased attention has centered on exploiting hypoxia in tumors for targeting the design of selective antitumor agents. This review presents an update of the principal families of compounds under study and in clinical trials, such as Noxide derivatives, nitro compounds and quinone derivatives. Especially promising for bioreductive activation is the reduction of some moieties able to trigger a mechanism that releases cytotoxic antitumor drugs. The most remarkable redox-activated triggers are presented, N-oxide, nitro, azido, quinone, metal ions, 1,2-benzisoxazolyl and sulfoxide moieties.