Summary:Purpose: Valproic acid (VPA), one of the widely used antiepileptic drugs (AEDs), was recently found to inhibit histone deacetylases (HDACs). HDAC inhibitors of a wide range of structures, such as hydroxamic acids, carboxylic acids, and cyclic tetrapeptides, have various effects on transformed and nontransformed cells, including neuromodulation and neuroprotection. The aim of this study was to assess comparatively the activity of traditional and newer AEDs as HDAC inhibitors.Methods: After incubation of HeLa cells with the tested AEDs, histone hyperacetylation was assessed by immunoblotting with an antibody specific to acetylated histone H4. Direct HDAC inhibition by AEDs was estimated by using HeLa nuclear extract as an HDACs source and an acetylated lysine substrate.Results: We found that in addition to VPA, topiramate (TPM) inhibited HDACs with apparent K i values of 2.22 ± 0.67 mM.Although levetiracetam (LEV) had no direct effect on HDACs, its major carboxylic acid metabolite in humans, 2-pyrrolidinonen-butyric acid (PBA), inhibited HDACs with K i values of 2.25 ± 0.78 mM. The AEDs LEV, phenobarbital, phenytoin, carbamazepine, ethosuximide, gabapentin, and vigabatrin did not inhibit HDACs. The compounds that directly inhibited HDACs also induced the accumulation of acetylated histone H4 in HeLa cells. The effects of TPM and PBA on histone acetylation were significant at 0.25 mM and 1 mM, respectively.Conclusions: We found that in addition to VPA, the newer AED TPM and the major metabolite of LEV, PBA, are able to induce histone hyperacetylation in human cells, although with lower potencies than VPA.

Our results point to the placenta as a novel target of VPA, implying potential involvement of the placenta in VPA's adverse fetal outcomes.

c Amphotericin B (AMB) is an effective antifungal agent. However, its therapeutic use is hampered by its toxicity, mainly due to channel formation across kidney cell membranes and the disruption of postendocytic trafficking. We previously described a safe injectable AMB-arabinogalactan (AG) conjugate with neutralized toxicity. Here we studied the mechanism of the toxicity of free AMB and its neutralization by conjugation with AG. AMB treatment of a kidney cell line modulated the trafficking of three receptors (C-X-C chemokine receptor type 4 [CXCR4], M1 receptor, and human transferrin receptor [hTfnR]) due to an increase in endosomal pH. Similar data were also obtained in yeast but with an increase in vacuolar pH and the perturbation of Hxt2-green fluorescent protein (GFP) trafficking. The conjugation of AMB with AG neutralized all elements of the toxic activity of AMB in mammalian but not in fungal cells. Based on these results, we provide an explanation of how the conjugation of AMB with AG neutralizes its toxicity in mammalian cells and add to the knowledge of the mechanism of action of free AMB in both fungal and mammalian cells. Opportunistic fungal infections have emerged as an important cause of morbidity and mortality in immunodeficient patients (34). Amphotericin B (AMB) is considered one of the most effective antifungal agents; it exhibits wide-spectrum activity against both filamentous and yeast-like fungi, its pharmacokinetic and pharmacodynamic profiles are superior to those of other antifungal agents, and it is fungicidal, in contrast to most azoles which are fungistatic (3,39,53). The fungicidal effect is important, since most patients suffering from invasive fungal infections are immunocompromised (34). However, the infusionrelated and cumulative toxicities, particularly nephrotoxicity (14,20,30), of AMB have resulted in reductions in the routine use of deoxycholate micellar AMB formulations and the development of less-toxic high-cost lipid AMB formulations (16,36). To develop a soluble, less-toxic, and less costly formulation, AMB has been conjugated with various soluble macromolecules (18,37,(47)(48)(49).We conjugated AMB with arabinogalactan (AG) (18), which significantly increased the water solubility of AMB, reduced its toxicity, and resulted in an efficacy similar to that of Fungizone (a deoxycholate micellar formulation) and AmBisome (a lipid-based formulation) (18). AMB-related toxicity is associated with the inductions of interleukin 1␤ (IL-1␤), tumor necrosis factor ␣ (TNF-␣), and apoptosis in organs. These effects were not observed with the AMB-AG conjugate (AMB-AGC), suggesting its potential as a safer formulation for therapeutic use (19). AG is an inexpensive natural product, and the conjugation reactions are performed at room temperature, revealing promise for a potentially low-cost drug. AMB penetrates the plasma membrane (PM) and interacts with its sterols to form transmembrane channels, resulting in the leakage of monovalent ions and metabolites, which leads to cell death (5,22,4...

Clathrin and caveolins are known for their involvement in the internalization of numerous receptors. Here we show that in polarized epithelial Madin-Darby canine kidney cells, both the clathrin machinery and caveolins are involved in the endocytosis and delivery to the plasma membrane (PM) of the M1 muscarinic acetylcholine receptor (mAChR). We initially localized this receptor to the lateral membrane, where it accumulates proximal to the tight junctions. From there it is internalized through the clathrin-mediated pathway. In addition, the receptor may associate on the PM with caveolin (cav) 2 or in intracellular compartments with either cav 2, or monomeric or oligomeric cav 1. Association of the PM M1 mAChR with cav 2 inhibits receptor endocytosis through the clathrin-mediated pathway or retains the receptor in an intracellular compartment. This intracellular association attenuates receptor trafficking. Expression of cav 1 with cav 2 rescues the latter's inhibitory effect. The caveolins stimulate M1 mAChR oligomerization thus maintaining a constant amount of monomeric receptor. These results provide evidence that caveolins play a role in the attenuation of the M1 muscarinic receptor's intracellular trafficking to and from the PM. INTRODUCTIONEndocytosis and the events leading up to it are of prime importance as they enable cells to regulate receptor-dependent signaling pathways as well as a variety of cellular functions. Clathrin-mediated endocytosis (CME) is the most well-characterized pathway for the internalization of soluble macromolecules and integral membrane proteins from the plasma membrane (PM; Conner and Schmid, 2003). G-protein-coupled receptors (GPCRs), being the largest receptor group, resort to a unique set of events that couple signaling and endocytosis (von Zastrow, 2003). Within the GPCRs, the muscarinic acetylcholine receptors (mAChRs) mediate the acetylcholine-dependent stimulus and are, therefore, highly regulated by G-protein activation and receptor endocytosis. In mammals, five distinct mAChR subtypes (M1-M5) exist. The M1, M3, and M5 mAChRs are coupled to the G␣q/11 and G␣q13 G proteins, leading to, for example, activation of phospholipase C (PLC) and phospholipase D (PLD), which have been shown to affect endocytosis (Shen et al., 2001); M2 and M4 mAChRs activate Gi proteins, leading to the inhibition of adenylyl cyclase (van Koppen and Kaiser, 2003). The different mAChR subtypes display unique, but not exclusive, expression patterns in the CNS and peripheral organs, such as the heart, epithelial exocrine glands, and smooth muscle tissue (Matsui et al., 2004). Activation of mAChRs has been found to elicit pigment-granule dispersion in retinal pigment epithelium, which is blocked by antagonist specific to M1 and M3 mAChRs (Phatarpekar et al., 2005). A study performed on human conjunctival epithelium revealed the expression of all five mAChRs. Specifically, M1 mAChRs were detected only intracellularly, but were mobilized to the PM when cholera toxin and hydrocortisone were omitted from the ...

In epithelial cells, the apical junctional complex (AJC), composed of tight junctions (TJs) and adherens junctions (AJs), maintains cell-surface polarity by forming a fence that prevents lateral movement and diffusion of proteins and lipids between the apical and basolateral PM and holds the epithelial monolayer intact through cell-cell contacts. Disassembly of this complex is a prime event in development and cell transformation. Maintenance of the AJC has been shown to involve mainly the actin cytoskeleton. Recent findings also point to the involvement of the microtubule (MT) system. Here we show the first evidence that in polarized epithelial MDCK cells, ARF-like protein 2 (ARL2) and beta-tubulin cofactor D, known to be involved in MT dynamics, have a role in disassembly of the AJC followed by cell dissociation from the epithelial monolayer, which is not dependent on MT depolymerization. In addition, we show that beta-tubulin cofactor D is partially localized to the lateral PM through its 15 C-terminal amino acids and intact MTs. ARL2 inhibited beta-tubulin cofactor D-dependent cell dissociation from the monolayer and AJC disassembly. To our knowledge, this is the first evidence that beta-tubulin cofactor D plays a role in cells independent of its presumed role in folding tubulin heterodimers. We conclude that ARL2 and beta-tubulin cofactor D participate in AJC disassembly and epithelial depolarization.