Design, synthesis, and biological evaluation of HDAC6 inhibitors targeting L1 loop and serine 531 residue

Histone deacetylases (HDACs) are a group of enzymes that remove acetyl groups from histones, leading to the silencing of genes. Targeting specific isoforms of HDACs has emerged as a promising approach for cancer therapy, as it can overcome drawbacks associated with pan-HDAC inhibitors. HDAC6 is a unique HDAC isoform that deacetylates non-histone proteins and is primarily located in the cytoplasm. It also has two catalytic domains and a zinc-finger ubiquitin binding domain (Zf-UBD) unlike other HDACs. HDAC6 plays a critical role in various cellular processes, including cell motility, protein degradation, cell proliferation, and transcription. Hence, the deregulation of HDAC6 is associated with various malignancies. In this study, we report the design and synthesis of a series of HDAC6 inhibitors. We evaluated the synthesized compounds by HDAC enzyme assay and identified that compound 8g exhibited an IC50 value of 21 nM and 40-fold selective activity towards HDAC6. We also assessed the effect of compound 8g on various cell lines and determined its ability to increase protein acetylation levels by Western blotting. Furthermore, the increased acetylation of α-tubulin resulted in microtubule polymerization and changes in cell morphology. Our molecular docking study supported these findings by demonstrating that compound 8g binds well to the catalytic pocket via L1 loop of HDAC6 enzyme. Altogether, compound 8g represents a preferential HDAC6 inhibitor that could serve as a lead for the development of more potent and specific inhibitors.

SPC-180002, a SIRT1/3 dual inhibitor, impairs mitochondrial function and redox homeostasis and represents an antitumor activity

Since sirtuins (SIRTs) are closely associated with reactive oxygen species (ROS) and antioxidant system, the development of their selective inhibitors is drawing attention for understanding of cellular redox homeostasis. Here, we describe the pharmacological properties of SPC-180002, which incorporates a methyl methacrylate group as a key pharmacophore, along with its comprehensive molecular mechanism as a novel dual inhibitor of SIRT1/3. The dual inhibition of SIRT1/3 by SPC-180002 disturbs redox homeostasis via ROS generation, which leads to an increase in both p21 protein stability and mitochondrial dysfunction. Increased p21 interacts with and inhibits CDK, thereby interfering with cell cycle progression. SPC-180002 leads to mitochondrial dysfunction by inhibiting mitophagy, which is accompanied by a reduction in oxygen consumption rate. Consequently, SPC-180002 strongly suppresses the proliferation of cancer cells and exerts anticancer effect in vivo. Taken together, the novel SIRT1/3 dual inhibitor, SPC-180002, impairs mitochondrial function and redox homeostasis, thereby strongly inhibiting cell cycle progression and cancer cell growth.

Exploring new histone deacetylase 6 inhibitors and their effects on reversing the α-tubulin deacetylation and cell morphology changes caused by methamphetamine

Indazole-based HDAC6 inhibitors with novel zinc-binding modifications were synthesized and evaluated to determine their potential to inhibit HDAC6. The analogs were subjected to a histone deacetylase (HDAC) enzyme assay, which led to identification of compounds 3a and 3b. Both compounds demonstrated higher potency and selectivity as HDAC6 inhibitors with IC50 values of 9.1 nM and 9.0 nM, respectively, and highlighted the importance of the hydroxamic acid moiety for binding to Zn2+ inside the catalytic pocket of HDAC enzymes. In the neuroblastoma SH-SY5Y cell line, both compounds efficiently acetylated α-tubulin but not histone H3 at a low concentration of 0.5 µM. Moreover, compounds 3a and 3b effectively reversed the deacetylation of α-tubulin caused by methamphetamine in the SH-SY5Y cell line, suggesting the potential usefulness of HDAC6 selective inhibition in restoring blood brain barrier integrity by reversing methamphetamine-induced deacetylation.

Design, synthesis, and biological evaluation of histone deacetylase inhibitor with novel salicylamide zinc binding group

INTRODUCTION

Histone deacetylases (HDACs) have emerged as important therapeutic targets for various diseases, such as cancer and neurological disorders. Although a majority of HDAC inhibitors use hydroxamic acids as zinc binding groups, hydroxamic acid zinc-binding groups suffer from poor bioavailability and nonspecific metal-binding properties, necessitating a new zinc-binding group. Salicylic acid and its derivatives, well-known for their therapeutic value, have also been reported to chelate zinc ions in a bidentate fashion. This drew our attention towards replacing hydroxamic acid with salicylamide as a zinc-binding group.

METHODS

In this study, for the first time, compound 5 possessing a novel salicylamide zinc-binding group was synthesized and evaluated biologically for its ability to inhibit various HDAC isoforms and induce acetylation upon α-tubulin and histone H3 among MDA-MB-231 cells.

RESULTS

Compound 5 exhibits selective inhibition against class I HDAC isoforms (HDAC1, 2, and 3) over class II and IV HDAC isoforms (HDAC4, 6, and 11). The exposure of MDA-MB-231 cells to compound 5 efficiently induced the acetylation of more histone H3 than α-tubulin, suggesting that compound 5 is a class I selective HDAC inhibitor. Moreover, the molecular docking study indicated that the salicylamide zinc-binding group of compound 5 coordinates the active zinc ion of class I HDAC2 in a bidentate fashion.

CONCLUSION

Overall, salicylamide represents a novel zinc-binding group for the development of class I selective HDAC inhibitors.

GRAPHICAL ABSTRACT

(http://links.lww.com/MD/G668).

Simvastatin-loaded solid lipid nanoparticles for enhanced anti-hyperlipidemic activity in hyperlipidemia animal model

The objective of current study was to develop solid lipid nanoparticles-loaded with simvastatin (SIM-SLNs) and investigate their in vivo anti-hyperlipidemic activity in poloxamer-induced hyperlipidemia model. Nano-template engineering technique was used to prepare SIM-SLNs with palmityl alcohol as lipid core and a mixture of Tween 40/Span 40/Myrj 52 to stabilize the core. The prepared SIM-SLNs were evaluated for physicochemical parameters including particle diameter, surface charge, morphology, incorporation efficiency, thermal behaviour and crystallinity. In vitro release profile of SIM-SLNs in simulated gastric and intestinal fluids was evaluated by using dialysis bag technique and anti-hyperlipidemic activity was assessed in hyperlipidemia rat model. SIM-SLNs revealed uniform particle size with spherical morphology, zeta potential of -24.9 mV and high incorporation efficiency (∼85%). Thermal behaviour and crystallinity studies demonstrated successful incorporation of SIM in the lipid core and its conversion to amorphous form. SIM-SLNs demonstrated a sustained SIM release from the lipid core of nanoparticles. SIM-SLNs significantly reduced the elevated serum lipids as indicated by ∼3.9 and ∼1.5-times decreased total cholesterol compared to those of untreated control and SIM dispersion treated hyperlipidemic rats. In conclusion, SIM-SLNs showed a great promise for improving the therapeutic outcomes of SIM via its effective oral delivery.

Marine-based waste stabilisation ponds: an evaluation of the hydraulic viability

Marine-Based Waste Stabilisation Ponds, formed by floating boom/skirt curtain enclosures anchored in sheltered waters, have recently been proposed for provision of low-cost effluent treatment facilities where land availability is limited in rapidly expanding coastal cities in the Third World. This paper outlines findings from a viability assessment, which drew on a preliminary site evaluation and baseline environmental survey (for a site in sheltered waters in the Far East), laboratory studies involving scale model tests in wave/wind/current flumes, and a structural and design loading study. It focuses on hydraulic and hydrodynamic considerations and reports the study's conclusions.

Novel boom/skirt systems for improvement of water quality in estuarial impoundments subject to saline influx

The recent popularity of esturial barrage construction in the UK has been driven largely by commercial and amenity interests arising from the need to rehabilitate tracts of derelict urban land. Formation of a permanent water body to replace the tidal regime hides unsightly mud banks and facilities ready access for water based recreation. Unfortunately, in most cases, and presumably arising from upstream extreme flood risk assessment, the barrier is designed to overtop under the highest (spring) tidal peaks so allowing a substantial influx of heavier saltwater into the impoundment on a regular basis. This might well substantially exceed influx via any navigational lock operations. The problem created by the salt water is that its greater density causes stratification in the impounded water body. In times of low freshwater flow little mixing takes place and the normal action of the wind, in circulating and aerating the water body, will only extend within the lighter and often thin surface freshwater layer. The consequence is that little reoxygenation of the lower layers takes place leading to depressed dissolved oxygen levels and possible anoxia. Sluice provision in the barrage may be ineffective in expelling the saline layers, so this water remains near stagnant and deteriorates in quality due to sediment oxygen demands until a major fluvial flood, or new saline influx, is able to effectively mix the waters. Conventional continuous surface releases through fish pass and/or by crest overspill ensure the preferential release of the freshwater rather than the problematic saltwater. Retrofitting of novel low cost floating boom/skirt baffle system is proposed here for alleviation of the problem.

Upper limb in injuries in dry ski slope skiing--a continuing problem

The aim of this study was to assess how common injuries to the upper limbs are from dry ski slope skiing, to document the pattern of injury to the upper limbs from dry ski slope skiing and to discuss preventative measures. Skier's experience was also determined. The study was carried out on 174 patients attending the accident and emergency department over a period of 3 years who had sustained injuries from dry ski slope skiing. Prospective registration was used to collect the data. Sixty-seven per cent of the patients had received instructions prior to skiing. Upper limb injuries outnumbered lower limb injuries by a ratio of 7.9 to 1. Thumb injuries outnumbered other injuries in the upper limb. The mechanism of injury was due to a fall in 94.2% of patients. It is concluded that the lattice network on dry ski slopes significantly contributes to the platform of injuries to the upper limbs, and ways in which the lattice network may be improved are recommended.