Although many reports have revealed the importance of defective microglia-mediated amyloid β phagocytosis in Alzheimer’s disease (AD), the underlying mechanism remains to be explored. Here we demonstrate that neurons in the brains of patients with AD and AD mice show reduction of sphingosine kinase1 (SphK1), leading to defective microglial phagocytosis and dysfunction of inflammation resolution due to decreased secretion of specialized proresolving mediators (SPMs). Elevation of SphK1 increased SPMs secretion, especially 15-R-Lipoxin A4, by promoting acetylation of serine residue 565 (S565) of cyclooxygenase2 (COX2) using acetyl-CoA, resulting in improvement of AD-like pathology in APP/PS1 mice. In contrast, conditional SphK1 deficiency in neurons reduced SPMs secretion and abnormal phagocytosis similar to AD. Together, these results uncover a novel mechanism of SphK1 pathogenesis in AD, in which impaired SPMs secretion leads to defective microglial phagocytosis, and suggests that SphK1 in neurons has acetyl-CoA-dependent cytoplasmic acetyltransferase activity towards COX2.

Expression of the ␥-glutamylcysteine synthetase heavy subunit (␥-GCSh), which encodes the rate-limiting enzymes for glutathione biosynthesis, is regulated by many cytotoxic agents. Moreover, ␥-GCSh mRNA expression is elevated in colorectal cancer, but how ␥-GCSh expression is regulated is not completely understood. By using actinomycin D, which inhibits new RNA synthesis, we showed that treatment of human colorectal cancer cells with the prooxidant sulindac increased the half-life of ␥-GCSh mRNA. By using a tetracyclineregulated ␥-GCSh mRNA assay system, we systematically dissected the cis-acting sequence and trans-acting factors that regulate the stability of ␥-GCSh by cytotoxic prooxidants. We demonstrated that a HuR recognition sequence, AUUUA, in the 3-untranslated region is responsible for the decay of ␥-GCSh mRNA. Oxidative stress enhanced cytoplasmic content of HuR. Overexpression of HuR by transfection stabilized ␥-GCSh mRNA, whereas overexpression of a dominant-negative HuR mutant suppressed the induced stability. Furthermore, prooxidant-induced ␥-GCSh mRNA stabilization and HuR binding were blocked by p38 mitogen-activated protein kinase inhibitors. We provide the first evidence that reduction-oxidation regulation of ␥-GCSh expression, itself a reduction-oxidation sensor and regulator, is mediated at least in part by the p38 mitogenactivated protein kinase signaling through the HuR RNA-binding protein.

As a central feature of neuroinflammation, microglial dysfunction has been increasingly considered a causative factor of neurodegeneration implicating an intertwined pathology with amyloidogenic proteins. Herein, we report the smallest synthetic molecule (N,N′-diacetyl-p-phenylenediamine [DAPPD]), simply composed of a benzene ring with 2 acetamide groups at the para position, known to date as a chemical reagent that is able to promote the phagocytic aptitude of microglia and subsequently ameliorate cognitive defects. Based on our mechanistic investigations in vitro and in vivo, 1) the capability of DAPPD to restore microglial phagocytosis is responsible for diminishing the accumulation of amyloid-β (Aβ) species and significantly improving cognitive function in the brains of 2 types of Alzheimer’s disease (AD) transgenic mice, and 2) the rectification of microglial function by DAPPD is a result of its ability to suppress the expression of NLRP3 inflammasome-associated proteins through its impact on the NF-κB pathway. Overall, our in vitro and in vivo investigations on efficacies and molecular-level mechanisms demonstrate the ability of DAPPD to regulate microglial function, suppress neuroinflammation, foster cerebral Aβ clearance, and attenuate cognitive deficits in AD transgenic mouse models. Discovery of such antineuroinflammatory compounds signifies the potential in discovering effective therapeutic molecules against AD-associated neurodegeneration.

Recent studies have shown that the mammalian high-affinity copper transporter encoded by Ctr1 is involved in the uptake of cisplatin. However, the roles of hCtr1 in cisplatin-sensitive and cisplatin-resistant mammalian cells have not been investigated. Here, we show that, of five cisplatin-resistant cell lines, only one (SR2) exhibited substantial reduction in hCtr1 expression as compared with that in its sensitive line small cell lung cancers (SCLC), whereas copper efflux transporters ATP7A and ATP7B were not significantly altered. SR2 exhibited cross-resistance to carboplatin but not to oxaliplatin. Transfection of expression hemagglutinin-tagged hCtr1 cDNA into SCLC and SR2 cells enhanced the uptake of copper, cisplatin, carboplatin, and oxaliplatin, suggesting that hCtr1 transporter can transport these platinum-based drugs. Whereas increased sensitivities to all these platinum drugs were observed in hCtr1-transfected SCLC cells, increased sensitivities to cisplatin and carboplatin but not to oxaliplatin were observed in hCtr1-transfected SR2 cells. These results suggest that SR2 acquired an additional unique intracellular resistance mechanism to oxaliplatin. Finally, using hCtr1 deletion mutants, we showed that the NH2-terminal domain of hCtr1 was involved in transporting all these platinum-based antitumor agents. These results collectively show the importance of hCtr1 in the transport of platinum-based antitumor agents in cisplatin-sensitive and cisplatin-resistant variants.

Genetic polymorphisms of the organic cation transporter 2 (OCT2), encoded by SLC22A2, have been investigated in association with metformin disposition. A functional decrease in transport function has been shown to be associated with the OCT2 variants. Using metabolomics, our study aims at a comprehensive monitoring of primary metabolite changes in order to understand biochemical alteration associated with OCT2 polymorphisms and discovery of potential endogenous metabolites related to the genetic variation of OCT2. Using GC-TOF MS based metabolite profiling, clear clustering of samples was observed in Partial Least Square Discriminant Analysis, showing that metabolic profiles were linked to the genetic variants of OCT2. Tryptophan and uridine presented the most significant alteration in SLC22A2-808TT homozygous and the SLC22A2-808G>T heterozygous variants relative to the reference. Particularly tryptophan showed gene-dose effects of transporter activity according to OCT2 genotypes and the greatest linear association with the pharmacokinetic parameters (Clrenal, Clsec, Cl/F/kg, and Vd/F/kg) of metformin. An inhibition assay demonstrated the inhibitory effect of tryptophan on the uptake of 1-methyl-4-phenyl pyrinidium in a concentration dependent manner and subsequent uptake experiment revealed differential tryptophan-uptake rate in the oocytes expressing OCT2 reference and variant (808G>T). Our results collectively indicate tryptophan can serve as one of the endogenous substrate for the OCT2 as well as a biomarker candidate indicating the variability of the transport activity of OCT2.