HIV-1 Envelope Spike MPER: From a Vaccine Target to a New Druggable Pocket for Novel and Effective Fusion Inhibitors.

Here we highlight a sound and unique work reported by Chen and co-workers entitled "HIV-1 fusion inhibitors targeting the membrane-proximal external region of Env spikes" (Xiao et al., Nat. Chem. Biol. 2020, 16, 529). In this article, the authors identify, by means of a clever antibody-guided strategy, several small molecules as fusion inhibitors of HIV-1 replication acting at the membrane proximal external region (MPER) of the HIV-1 envelope (Env) spike. MPER, which was previously recognized as a vaccine target, emerges as a novel druggable target for the discovery of HIV-1 fusion inhibitors. The compounds (exemplified by dequalinium and dequalinium-inspired analogues) prevent the conformational changes of Env from the prefusion species to the intermediate states required for membrane fusion. This work not only paves the way to novel, specific and useful anti-HIV-1 inhibitors, but also discloses new therapeutic strategies against other infectious diseases.

Dequalinium blocks macrophage-induced metastasis following local radiation.

A major therapeutic obstacle in clinical oncology is intrinsic or acquired resistance to therapy, leading to subsequent relapse. We have previously shown that systemic administration of different cytotoxic drugs can induce a host response that contributes to tumor angiogenesis, regrowth and metastasis. Here we characterize the host response to a single dose of local radiation, and its contribution to tumor progression and metastasis. We show that plasma from locally irradiated mice increases the migratory and invasive properties of colon carcinoma cells. Furthermore, locally irradiated mice intravenously injected with CT26 colon carcinoma cells succumb to pulmonary metastasis earlier than their respective controls. Consequently, orthotopically implanted SW480 human colon carcinoma cells in mice that underwent radiation, exhibited increased metastasis to the lungs and liver compared to their control tumors. The irradiated tumors exhibited an increase in the colonization of macrophages compared to their respective controls; and macrophage depletion in irradiated tumor-bearing mice reduces the number of metastatic lesions. Finally, the anti-tumor agent, dequalinium-14, in addition to its anti-tumor effect, reduces macrophage motility, inhibits macrophage infiltration of irradiated tumors and reduces the extent of metastasis in locally irradiated mice. Overall, this study demonstrates the adverse effects of local radiation on the host that result in macrophage-induced metastasis.

Towards boron neutron capture therapy: the formulation and preliminary in vitro evaluation of liposomal vehicles for the therapeutic delivery of the dequalinium salt of bis-nido-carborane.

Liposomes of phosphatidylcholine or of dimyristoylphosphatidylcholine that incorporate bis-nido-carborane dequalinium salt are stable in physiologically relevant media and have in vitro toxicity profiles that appear to be compatible with potential therapeutic applications. These features render the structures suitable candidate boron-delivery vehicles for evaluation in the boron neutron capture therapy of cancer.

Exercise-induced cardioprotection is impaired by anabolic steroid treatment through a redox-dependent mechanism.

High doses of anabolic androgenic steroids (AAS) impair the cardioprotective effects of exercise against ischemia/reperfusion (I/R) insult, possibly through cellular redox imbalance. Here, the effect of nandrolone decanoate (DECA) treatment on heart redox metabolism was investigated during I/R in sedentary and exercised rats. DECA treatment significantly reduced superoxide dismutase and glutathione reductase activities in exercised rats after heart reperfusion. Catalase and glutathione peroxidase activities were not affected by DECA in both sedentary and trained rats, regardless the I/R period. DECA also induced myocardial oxidative stress, as evidenced by the reduced levels of total reduced thiols after heart reperfusion in exercised rats treated with the anabolic steroid. These results indicate that cardiotoxic effects of supraphysiological doses of AAS involve reduced heart antioxidant capacity.

Selective targeting of neuroblastoma tumour-initiating cells by compounds identified in stem cell-based small molecule screens.

Neuroblastoma (NB) is the most deadly extra-cranial solid tumour in children necessitating an urgent need for effective and less toxic treatments. One reason for the lack of efficacious treatments may be the inability of existing drugs to target the tumour-initiating or cancer stem cell population responsible for sustaining tumour growth, metastases and relapse. Here, we describe a strategy to identify compounds that selectively target patient-derived cancer stem cell-like tumour-initiating cells (TICs) while sparing normal paediatric stem cells (skin-derived precursors, SKPs) and characterize two therapeutic candidates. DECA-14 and rapamycin were identified as NB TIC-selective agents. Both compounds induced TIC death at nanomolar concentrations in vitro, significantly reduced NB xenograft tumour weight in vivo, and dramatically decreased self-renewal or tumour-initiation capacity in treated tumours. These results demonstrate that differential drug sensitivities between TICs and normal paediatric stem cells can be exploited to identify novel, patient-specific and potentially less toxic therapies.

New method for the quantification of dequalinium cations in pharmaceutical samples by absorption and fluorescence diode array thin-layer chromatography.

A diode array HPTLC method for dequalinium chloride in pharmaceutical preparations is presented. For separation a Nano TLC silica gel plate (Merck) is used with the mobile phase methanol-7.8% aqueous NH(4)(+)CH(3)COO(-) (17:3, v/v) over a distance of 6 cm. Dequalinium chloride shows an R(F) value of 0.58. Pure dequalinium chloride is measured in the wavelength range from 200 to 500 nm and shows several by-products, contour plot visualized in absorption, fluorescence and using the Kubelka-Munk transformation. Scanning of a single track in absorption and fluorescence measuring 600 spectra in the range from 200 to 1100 nm takes 30s. As a sample pre-treatment of an ointment it is simply dissolved in methanol and can be quantified in absorption from 315 to 340 nm. The same separation can also be quantified using fluorescence spectrometry in the range from 355 to 370 nm. A new staining method for dequalinium chloride, using sodium tetraphenyl borate/HCl in water allows a fluorescence quantification in the range from 445 to 485 nm. The linearity range of absorption and fluorescence measurements is from 10 to 2000 ng. Sugar-containing preparations like liquids or lozenges with a reduced sample pre-treatment can be reliably quantified only in fluorescence. The total for the quantification of an ointment sample (measuring four standards and five samples), including all sample pre-treatment steps takes less than 45 min!

Inhibition of protein kinase C by dequalinium analogues: structure-activity studies on head group variations.

New dequalinium analogues and related heteroaromatic systems were synthesized and evaluated for inhibition of protein kinase Calpha. In vitro assays with recombinant human PKCalpha showed that the number of the aromatic ring head groups as well as their electron-richness, are critical factors that determine potency. The inhibitory strengths of the synthesized compounds are shown to correlate well with Mulliken charges on the head group ring nitrogen atoms making it possible to design likely candidate molecules having improved protein kinase Calpha inhibitory activity.

The receptor for activated C-kinase-I (RACK-I) anchors activated PKC-beta on melanosomes.

Protein kinase C (PKC), a family of at least eleven isoforms, mediates numerous cell functions. In human melanocytes, alpha, beta, delta, epsilon and zeta isoforms of PKC are expressed, but uniquely PKC-beta activates tyrosinase, the key and the rate-limiting enzyme in melanogenesis, by phosphorylating specific serine residues on its cytoplasmic domain. To investigate the mechanism by which only PKC-beta phosphorylates tyrosinase, we examined the expression of receptor for activated C-kinase-I (RACK-I), a receptor specific for activated PKC-beta, on the surface of melanosomes, the specialized organelle in which melanogenesis occurs. Immunoblot analysis of purified melanosomes revealed that RACK-I is readily detectable. Immunoprecipitation of RACK-I from purified melanosomes, followed by immunoblot analysis using antibody against PKC-beta, revealed abundant PKC-beta, whereas PKC-alpha was not detected when immunoblot analysis was performed using antibody against PKC-alpha. Activation of PKC in melanocytes increased the level of PKC-beta co-immunoprecipitated with RACK-I, while the level of melanosome-associated RACK-I decreased when melanocytes were treated chronically with the 12-0-tetradecanoyl-phorbol 13-Acetate (TPA), a condition known to deplete PKC and reduce tyrosinase activity. Immunoprecipitation with RACK-I antibody co-precipitated fewer PKC-beta in the presence of UV-activated 1, 1'-decamethylenebis-4-aminoquinaldinium di-iodide (DECA), known to disrupt the interaction between activated PKC-beta and RACK-I. Treatment of intact melanocytes with DECA also decreased tyrosinase activity. Moreover, suppression of RACK-I expression by transfecting melanocytes with siRNA against RACK-I reduced the basal tyrosinase activity and blocked TPA-induced increases in tyrosinase activity. Taken together, these results demonstrate that RACK-I anchors activated PKC-beta on the melanosome membrane, allowing PKC-beta to phosphorylate tyrosinase.

Isothermic titration calorimetry to study CMCs of neutral surfactants and of the liposome-forming bolaamphiphile dequalinium.

Isothermic titration calorimetry was used to measure the heat of micelle formation (molar enthalpy of transfer of surfactants monomers from water into micellar aggregates. The problems associated with the estimation of the CMC and the whole therodynamic profile of micellization of surfactants via Gibbs-Helmholtz-Equation are discussed. CMC's of octylthioglucoside and the peculiar bolaamphilphile dequalinium which concentrates in mitochondria are measured. In contrast to earlier reports, no CMC of dequalinium could be found inspite of extensive systematic measurements.

Comparative in vitro evaluation of dequalinium B, a new boron carrier for neutron capture therapy (NCT).

A boronated derivative of dequalinium, a delocalized lipophilic cation (DLC), was synthesized as a potential boron carrier for the selective targeting of mitochondria in malignant versus benign cells for boron neutron capture therapy (BNCT), a binary modality for the treatment of cancer. This agent, designated DEQ-B, was taken up and retained in vitro in the KB, F98, and C6 tumor cell lines but not in the normal epithelial cell line CV1. DEQ-B was also less toxic in the latter cell line at lower exposure concentrations The uptake, retention, and toxicity profiles of DEQ-B are comparable to those of the non-boronated DLCs, dequalinium, MKT 077, RH 123, and tetraphenylphosphonium chloride. Our results suggest that the synthesis and further evaluation of boronated DLCs as potential delivery agents for BNCT is warranted.

Compounds that block both intermediate-conductance (IK(Ca)) and small-conductance (SK(Ca)) calcium-activated potassium channels.

1. Nine bis-quinolinyl and bis-quinolinium compounds related to dequalinium, and previously shown to block apamin-sensitive small conductance Ca(2+)-activated K(+) channels (SK(Ca)), have been tested for their inhibitory effects on actions mediated by intermediate conductance Ca(2+)-activated K(+) channels (IK(Ca)) in rabbit blood cells. 2. In most experiments, a K(+)-sensitive electrode was employed to monitor the IK(Ca)-mediated net loss of cell K(+) that followed the addition of the Ca(2+) ionophore A23187 (2 microM) to red cells suspended at an haematocrit of 1% in a low K(+) (0.12 - 0.17 mM) solution. The remainder used an optical method based on measuring the reduction in light transmission that occurred on applying A23187 (0.4 or 2 microM) to a very dilute suspension of red cells (haematocrit 0.02%). 3. Of the compounds tested, the most potent IK(Ca) blocker was 1,12 bis[(2-methylquinolin-4-yl)amino]dodecane (UCL 1407) which had an IC(50) of 0.85+/-0.06 microM (mean+/-s.d. mean). 4. The inhibitory action of UCL 1407 and its three most active congeners was characterized by (i) a Hill slope greater than unity, (ii) sensitivity to an increase in external [K(+)], and (iii) a time course of onset that suggested use-dependence. Also, the potency of the nonquaternary compounds tested increased with their predicted lipophilicity. These findings suggested that the IK(Ca) blocking action resembles that of cetiedil rather than of clotrimazole. 5. Some quaternized members of the series were also active. The most potent was the monoquaternary UCL 1440 ((1-[N-[1-(3, 5-dimethoxybenzyl)-2-methylquinolinium-4-yl]amino]-10-[N'-(2-me thylqu inolinium-4yl)amino] decane (trifluoroacetate) which had an IC(50) of 1.8+/-0.1 microM. The corresponding bisquaternary UCL 1438 (1, 10-bis[N-[1-(3,5-dimethoxybenzyl)-2-methylquinolinium-4-yl]amino] decane bis(trifluoroacetate) was almost as active (IC(50) 2.7+/-0.3 microM). 6. A bis-aminoquinolium cyclophane (UCL 1684) had little IK(Ca) blocking action despite its great potency at SK(Ca) channels (IC(50) 4.1+/-0.2 nM). 7. The main outcome is the identification of new intermediate-conductance Ca(2+)-activated K(+) channel blockers with a wide range of IK(Ca)/SK(Ca) selectivities.

Inhibition of protein kinase C(alpha) by dequalinium analogues: dependence on linker length and geometry.

Analogues of a bipartite compound, dequalinium (DECA) (quinolinium, 1,1'-(1,10-decanediyl)bis(4-amino-2-methyl diiodide)), were tested for inhibition of protein kinase C(alpha) (PKC(alpha)). In vitro assays of monomeric and dimeric analogues support a model in which DECA inhibits PKC(alpha) by an obligatory two-point contact, a unique mechanism among PKC inhibitors. The presence of unsaturation in the center of the C(10)-alkyl linker produced geometric isomers with different inhibitory potencies: cis IC(50) = 52 +/- 12 microM and trans IC(50) = 12 +/- 3 microM, where the trans isomer was equipotent to that of the saturated C(10)-DECA. DECA analogues with longer, saturated linkers (C(12), C(14), or C(16)) exhibited enhanced inhibitory potencies which reached a plateau with the C(14)-linker (IC(50) = 2.6 +/- 0.2 microM). Metastatic melanoma cells treated with 250 nM C(12)-, C(14)-, or C(16)-DECA and irradiated with long-wave UV light (which causes irreversible inhibition of PKC(alpha) by DECA) confirmed the linker-dependent inhibition of intracellular PKC(alpha) activity.

Synthesis, molecular modeling, and K+ channel-blocking activity of dequalinium analogues having semirigid linkers.

Dequalinium [1,1'-(decane-1, 10-diyl)bis(2-methyl-4-aminoquinolinium)] is an effective blocker of the small conductance Ca2(+)-activated K+ channel. It has been shown that the number of methylene groups in the alkyl chain linking the two quinolinium rings of this type of molecule is not critical for activity. To further investigate the role of the linker, analogues of dequalinium have been synthesized, in which the alkyl chain has been replaced by CH2XCH2 where X is a rigid or semirigid group containing aromatic rings. The compounds have been tested for blockade of the slow after-hyperpolarization on rat sympathetic neurons. The most potent compounds have X = phenanthryl, fluorenyl, cis-stilbene, and C6H4(CH2)nC6H4, where n = 0-4. The conformational preferences of the compounds were investigated using the XED/COSMIC molecular modeling system. Although there is some dependence of the potency of the analogue on the conformational properties of the linker (X), overall, X groups having substantial structural differences are tolerated. It seems that X provides a support for the two quinolinium groups and does not interact with the channel directly. The intramolecular separation between the quinolinium rings, which is provided by rigid groups X, is not critical for activity; this may be attributed to the residual conformational mobility of the heterocycles and to the extensive delocalization of the positive charge. These two factors may permit favorable contacts between the quinolinium groups and the channel over a range of intramolecular separations.

Synthesis and quantitative structure-activity relationships of dequalinium analogues as K+ channel blockers: investigation into the role of the substituent at position 4 of the quinoline ring.

Dequalinium (4) is a potent and selective blocker of small conductance Ca2+-activated K+ channels, an important but relatively little studied class. The 4-NH2 group of dequalinium has been shown to contribute significantly to blocking potency. In this study, we have investigated further the role of the 4-NH2 group. Replacement of this group by other substituents (R4) and quantitative structure-activity relationship (QSAR) analysis on the resultant analogues have yielded a correlation between blocking potency and sigma R for R4 for seven of the compounds. The application of calculated electronic indices enabled the extension of the QSAR to compounds for which the appropriate sigma R values are not available, allowing all 13 analogues of this series to be included in the correlations. Analysis using electronic indices obtained from AM1 MO calculations on model compounds revealed that the blocking potency correlates with the partial charge on the ring N atom, ELUMO, and EHOMO. The EHOMO correlation is qualitatively inconsistent as the HOMO is not the same orbital in all compounds. The ELUMO correlation [pEMR = 1.19(+/- 0.21)ELUMO + 5.41(+/- 1.05), n = 13, r = 0.86, s = 0.274] suggests that the higher the ELUMO the more potent is the analogue. This is consistent with simple charge transfer from the channel to the blocker and may refer to other processes which are important for the strength of the drug-K+ channel interaction such as the desolvation of the compounds.

Synthesis and structure-activity relationships of dequalinium analogues as K+ channel blockers. Investigations on the role of the charged heterocycle.

Small conductance Ca(2+)-activated K+ (SKCa) channels occur in many cells but have been relatively little studied. Dequalinium, a bis-quinolinium compound, has recently been shown to be the most potent nonpeptidic blocker of this K+ channel subtype. This paper examines the importance of the quinolinium rings for blocking activity. Analogues of dequalinium were synthesised in which one quinolinium group was removed (1 and 2) or replaced by a triethylammonium group (3). They have been assayed in vitro for their ability to block the after-hyperpolarization (mediated by the opening of SKCa channels) that follows the action potential in rat sympathetic neurones. The compound having one quinolinium and one triethylammonium group (3) showed reduced activity, and it is suggested that the stronger binding to the channel of the quinolinium relative to the triethylammonium group may be related to differences in their electrostatic potential energy maps. Two monoquaternary compounds (1 and 2) were tested, but they exhibited a different pharmacological profile that did not allow definite conclusions to be drawn concerning their potency as blockers of the SKCa channel. Replacement of both quinolinium groups by pyridinium, acridinium, isoquinolinium, or benzimidazolium reduced but did not abolish activity. These results show that compounds having a number of different heterocyclic cations are capable of blocking the SKCa channel. However, among the heterocycles studied, quinoline is optimal. Furthermore, charge delocalization seems to be important: the higher the degree of delocalization the more potent the compound.

In vitro efficiency of endodontic irrigation solutions on protein desorption.

The use of irrigating solutions is widely accepted as a necessary adjunct to biomechanical preparation to obtain adequate cleansing of the root canal system. In this study, the efficiency of three solutions was tested in an in vitro experimental system for the removal of protein from apatite surfaces: Salvizol (a bis-dequalinium acetate solution) and sodium hypochlorite at 0.5, 1, 3 and 6% at pH 7.4 and 11.5. Buffered Tris-HCl solutions at pH 7.4 and 11.5 were used as controls. All chemicals showed rapid kinetics effects since no variation of the process could be detected after 5 min. Salvizol was the least efficient solution since it induced only a 2% protein desorption. Sodium hypochlorite efficiency increased with concentration to reach a 70% protein desorption from the apatite surface. In general, alkaline solutions were more efficient than buffered ones, and the ionic strength did not appear to have a major effect on the protein desorption process.

[Comparative study of chelates]. / Estudio comparativo de quelantes.

A comparative analysis of the in vitro quelating effect of Endodent, Largal Ultra and Salvident was done evaluating the decrease of dentine weight that they produced. The samples of dentine, each time included in the same volume of the three agents during 24 and 48 hours. Largal Ultra was in the 100% of the cases, the quelating that more decrease of weight produced.

[An evaluation of the antibacterial effectiveness of bisdequalinium acetate and sodium hypochlorite]. / Bis-deqalinium asetat ve sodyum hipoklorid solusyonlarinin antibakteriyel etkinliklerinin degerlendirilmesi.

The antimicrobial effectiveness of sodium hypochlorite and bis-dequalinium acetate was evaluated in vitro using three different microorganisms. The solutions were prepared in various concentrations and microorganisms were exposed to these solutions for 5, 10, 15 min. then placed into a culture medium, incubated and determined the presence or absence of growth. These results were compared with those obtained with phenol. The following conclusions were drawn from this study: 1. Of the solutions tested Bis-dequalinium acetate was the most effective antimicrobial agent. And 1.25/1000 Bis-dequalinium acetate is appropriate for the clinical use. 2. Sodium Hypochlorite is the least effective compared with Bis-dequalinium acetate and phenol. 2/100 NaOCl is agreeable for the clinical use. 3. Normal saline exhibits no antimicrobial properties.