A short-chain acyl-CoA synthetase that supports branched-chain fatty acid synthesis in Staphylococcus aureus.

Staphylococcus aureus controls its membrane biophysical properties using branched-chain fatty acids (BCFAs). The branched-chain acyl-CoA precursors, utilized to initiate fatty acid synthesis, are derived from branched-chain ketoacid dehydrogenase (Bkd), a multiprotein complex that converts α-keto acids to their corresponding acyl-CoAs; however, Bkd KO strains still contain BCFAs. Here, we show that commonly used rich medias contain substantial concentrations of short-chain acids, like 2-methylbutyric and isobutyric acids, that are incorporated into membrane BCFAs. Bkd-deficient strains cannot grow in defined medium unless it is supplemented with either 2-methylbutyric or isobutyric acid. We performed a screen of candidate KO strains and identified the methylbutyryl-CoA synthetase (mbcS gene; SAUSA300_2542) as required for the incorporation of 2-methylbutyric and isobutyric acids into phosphatidylglycerol. Our mass tracing experiments show that isobutyric acid is converted to isobutyryl-CoA that flows into the even-chain acyl-acyl carrier protein intermediates in the type II fatty acid biosynthesis elongation cycle. Furthermore, purified MbcS is an ATP-dependent acyl-CoA synthetase that selectively catalyzes the activation of 2-methylbutyrate and isobutyrate. We found that butyrate and isovalerate are poor MbcS substrates and activity was not detected with acetate or short-chain dicarboxylic acids. Thus, MbcS functions to convert extracellular 2-methylbutyric and isobutyric acids to their respective acyl-CoAs that are used by 3-ketoacyl-ACP synthase III (FabH) to initiate BCFA biosynthesis.

Malonyl-acyl carrier protein decarboxylase activity promotes fatty acid and cell envelope biosynthesis in Proteobacteria.

Bacterial fatty acid synthesis in Escherichia coli is initiated by the condensation of an acetyl-CoA with a malonyl-acyl carrier protein (ACP) by the ß-ketoacyl-ACP synthase III enzyme, FabH. E. coli ΔfabH knockout strains are viable because of the yiiD gene that allows FabH-independent fatty acid synthesis initiation. However, the molecular function of the yiiD gene product is not known. Here, we show the yiiD gene product is a malonyl-ACP decarboxylase (MadA). MadA has two independently folded domains: an amino-terminal N-acetyl transferase (GNAT) domain (MadAN) and a carboxy-terminal hot dog dimerization domain (MadAC) that encodes the malonyl-ACP decarboxylase function. Members of the proteobacterial Mad protein family are either two domain MadA (GNAT-hot dog) or standalone MadB (hot dog) decarboxylases. Using structure-guided, site-directed mutagenesis of MadB from Shewanella oneidensis, we identified Asn45 on a conserved catalytic loop as critical for decarboxylase activity. We also found that MadA, MadAC, or MadB expression all restored normal cell size and growth rates to an E. coli ΔfabH strain, whereas the expression of MadAN did not. Finally, we verified that GlmU, a bifunctional glucosamine-1-phosphate N-acetyl transferase/N-acetyl-glucosamine-1-phosphate uridylyltransferase that synthesizes the key intermediate UDP-GlcNAc, is an ACP binding protein. Acetyl-ACP is the preferred glucosamine-1-phosphate N-acetyl transferase/N-acetyl-glucosamine-1-phosphate uridylyltransferase substrate, in addition to being the substrate for the elongation-condensing enzymes FabB and FabF. Thus, we conclude that the Mad family of malonyl-ACP decarboxylases supplies acetyl-ACP to support the initiation of fatty acid, lipopolysaccharide, peptidoglycan, and enterobacterial common antigen biosynthesis in Proteobacteria.

Branched-chain amino acid metabolism controls membrane phospholipid structure in Staphylococcus aureus.

Branched-chain amino acids (primarily isoleucine) are important regulators of virulence and are converted to precursor molecules used to initiate fatty acid synthesis in Staphylococcus aureus. Defining how bacteria control their membrane phospholipid composition is key to understanding their adaptation to different environments. Here, we used mass tracing experiments to show that extracellular isoleucine is preferentially metabolized by the branched-chain ketoacid dehydrogenase complex, in contrast to valine, which is not efficiently converted to isobutyryl-CoA. This selectivity creates a ratio of anteiso:iso C5-CoAs that matches the anteiso:iso ratio in membrane phospholipids, indicating indiscriminate utilization of these precursors by the initiation condensing enzyme FabH. Lipidomics analysis showed that removal of isoleucine and leucine from the medium led to the replacement of phospholipid molecular species containing anteiso/iso 17- and 19-carbon fatty acids with 18- and 20-carbon straight-chain fatty acids. This compositional change is driven by an increase in the acetyl-CoA:C5-CoA ratio, enhancing the utilization of acetyl-CoA by FabH. The acyl carrier protein (ACP) pool normally consists of odd carbon acyl-ACP intermediates, but when branched-chain amino acids are absent from the environment, there was a large increase in even carbon acyl-ACP pathway intermediates. The high substrate selectivity of PlsC ensures that, in the presence or the absence of extracellular Ile/Leu, the 2-position is occupied by a branched-chain 15-carbon fatty acid. These metabolomic measurements show how the metabolism of isoleucine and leucine, rather than the selectivity of FabH, control the structure of membrane phospholipids.

Chemical Exchanges between Multilateral Symbionts.

Herein is a report on the molecular exchange occurring between multilateral symbiosis partners-a tit-for-tat exchange that led to the characterization of two new metabolites, conocandin B (fungal-derived) and dentigerumycin F (bacterial-derived). The structures were determined by NMR, mass spectrometry, genomic analysis, and chemical derivatizations. Conocandin B exhibits antimicrobial activity against both the bacterial symbionts of fungus-growing ant and human pathogenic strains by selectively inhibiting FabH, thus disrupting fatty acid biosynthesis.

Lyophilized Iron Oxide Nanoparticles Encapsulated in Amphotericin B: A Novel Targeted Nano Drug Delivery System for the Treatment of Systemic Fungal Infections.

We formulated and tested a targeted nanodrug delivery system to help treat life-threatening invasive fungal infections, such as cryptococcal meningitis. Various designs of iron oxide nanoparticles (IONP) (34-40 nm) coated with bovine serum albumin and coated and targeted with amphotericin B (AMB-IONP), were formulated by applying a layer-by-layer approach. The nanoparticles were monodispersed and spherical in shape, and the lead formulation was found to be in an optimum range for nanomedicine with size (≤36 nm), zeta potential (-20 mV), and poly dispersity index (≤0.2), and the drug loading was 13.6 ± 6.9 µg of AMB/mg of IONP. The drug release profile indicated a burst release of up to 3 h, followed by a sustained drug release of up to 72 h. The lead showed a time-dependent cellular uptake in C. albicans and C. glabrata clinical isolates, and exhibited an improved efficacy (16-25-fold) over a marketed conventional AMB-deoxycholate product in susceptibility testing. Intracellular trafficking of AMB-IONP by TEM and confocal laser scanning microscopy confirmed the successful delivery of the AMB payload at and/or inside the fungal cells leading to potential therapeutic advantages over the AMB-deoxycholate product. A short-term stability study at 5 °C and 25 °C for up to two months showed that the lyophilized form was stable.

Impact of the Major Candida glabrata Triazole Resistance Determinants on the Activity of the Novel Investigational Tetrazoles VT-1598 and VT-1161.

VT-1161 and VT-1598 are promising investigational tetrazole antifungals that have shown in vitro and in vivo activity against Candida and other fungi. Candida glabrata is a problematic opportunistic pathogen that is associated with high mortality in invasive infection, as well as both intrinsic and rapidly acquired antifungal resistance. The MICs of VT-1161 and VT-1598 were determined by CLSI methodology to evaluate their in vitro activities against clinical C. glabrata isolates and strains containing individual deletions of the zinc cluster transcription factor genes PDR1 and UPC2A as well as the efflux transporter genes CDR1, PDH1, and SNQ2 Overall, both tetrazoles demonstrated relative activities comparable to those of the tested triazole antifungals against clinical C. glabrata isolates (MIC range, 0.25 to 2 mg/liter and 0.5 to 2 µg/ml for VT-1161 and VT-1598, respectively). Deletion of the PDR1 gene in fluconazole-resistant matched clinical isolate SM3 abolished the decreased susceptibility phenotype completely for both VT-1161 and VT-1598, similarly to the triazoles. UPC2A deletion also increased susceptibility to both triazoles and tetrazoles but to a lesser extent than PDR1 deletion. Of the three major transporter genes regulated by Pdr1, CDR1 deletion resulted in the largest MIC reductions for all agents tested, while PDH1 and SNQ2 deletion individually impacted MICs very little. Overall, both VT-1161 and VT-1598 have comparable activities to those of the available triazoles, and decreased susceptibility to these tetrazoles in C. glabrata is driven by many of the same known resistance mechanisms.

Oleate hydratase from Staphylococcus aureus protects against palmitoleic acid, the major antimicrobial fatty acid produced by mammalian skin.

Oleate hydratases (OhyAs) belong to a large family of bacterial proteins catalyzing the hydration or isomerization of double bonds in unsaturated fatty acids. A Staphylococcus aureus gene (Sa0102) is predicted to encode an OhyA. Here, we recombinantly expressed and purified SaOhyA and found that it forms a homodimer that requires FAD for activity. SaOhyA hydrates only unsaturated fatty acids containing cis-9 double bonds, but not fatty acids with trans-9 double bonds or cis double bonds at other positions. SaOhyA products were not detected in S. aureus phospholipids and were released into the growth medium. S. aureus does not synthesize unsaturated fatty acids, and the SaOhyA substrates are derived from infection sites. Palmitoleate (16:1(9Z)) is a major mammalian skin-produced antimicrobial fatty acid that protects against S. aureus infection, and we observed that it is an SaOhyA substrate and that its hydroxylated derivative is not antimicrobial. Treatment of S. aureus with 24 µm 16:1(9Z) immediately arrested growth, followed by growth resumption after a lag period of 2 h. The ΔohyA mutant strain did not recover from the 16:1(9Z) challenge, and increasing SaOhyA expression using a plasmid system prevented the initial growth arrest. Challenging S. aureus with sapienic acid (16:1(6Z)), an antimicrobial fatty acid produced only by human skin, arrested growth without recovery in WT, ΔohyA, and SaOhyA-overexpressing strains. We conclude that SaOhyA protects S. aureus from palmitoleic acid, the antimicrobial unsaturated fatty acid produced by most mammals, and that sapienic acid, uniquely produced by humans, counters the OhyA-dependent bacterial defense mechanism.

Fact vs. Affect in the Telephone Game: All Levels of Surprise Are Retold With High Accuracy, Even Independently of Facts.

When people retell stories, what guides their retelling? Most previous research on story retelling and story comprehension has focused on information accuracy as the key measure of stability in transmission. This paper suggests that there is a second, affective, dimension that provides stability for retellings, namely the audience affect of surprise. In a large-sample study with multiple iterations of retellings, we found evidence that people are quite accurate in preserving all degrees of surprisingness in serial reproduction - even when the event that produced the surprisingness in the original story is dropped or changed. Thus, we propose that the preservation of affect is an implicit goal of retelling: merely do retellers not recall highly surprising events better, but rather they register all levels of surprisingness precisely and aim to surprise their implied audience to same degree. This study used 2,389 participants. Significance Statement: Story retelling is a process whereby cultural information is transmitted horizontally across social networks and vertically down generations. For the most part, retelling research has focused on the relevance and stability of factual information, "who did what, where, when, and why"; comparatively little is known about the transmission of affective information. We suggest that affect can serve as a second axis of stability for retelling, partially independent from factual information. In serial reproduction tasks modeled after the telephone game, we find that surprisingness of stories is well preserved across retellings - even when the facts and events of the story are not. The findings are significant for the communication of information, and thereby also the stability and transformation of culture in general.

Relative Contribution of the ABC Transporters Cdr1, Pdh1, and Snq2 to Azole Resistance in Candida glabrata.

The utility of the azole antifungals for the treatment of invasive candidiasis is severely hampered by azole resistance in Candida glabrata This resistance is mediated almost exclusively by activating mutations in the zinc cluster transcription factor Pdr1, which controls the genes encoding the multidrug resistance transporters Cdr1, Pdh1, and Snq2. However, the specific relative contributions of these transporters to resistance are not known. To address this question, the SAT1 flipper method was used to delete CDR1, PDH1, and SNQ2 in a strain of C. glabrata engineered to carry a clinically relevant activating mutation in PDR1 Susceptibility testing was performed according to the CLSI guidelines, with minor modifications, and confirmed with Etest strips. Of the single-transporter-deletion strains, only the CDR1 deletion resulted in a decreased azole MIC. The deletion of PDH1 in combination with CDR1 resulted in a moderate decrease in MIC compared to that observed with the deletion of CDR1 alone. SNQ2 deletion only decreased the MIC in the triple-deletion strain in the absence of both CDR1 and PDH1 The deletion of all three transporters in combination decreased the MIC to the level observed in the PDR1 deletion strains for some, but not all, azoles tested, which indicates that additional Pdr1 targets likely play a minor role in this process. These results indicate that while Cdr1 is the most important Pdr1-mediated multidrug resistance transporter for azole resistance in this clinical isolate, all three of these transporters contribute to its high-level resistance to the azole antifungals.

Jjj1 Is a Negative Regulator of Pdr1-Mediated Fluconazole Resistance in Candida glabrata.

The high prevalence of fluconazole resistance among clinical isolates of Candida glabrata has greatly hampered the utility of fluconazole for the treatment of invasive candidiasis. Fluconazole resistance in this yeast is almost exclusively due to activating mutations in the transcription factor Pdr1, which result in upregulation of the ABC transporter genes CDR1, PDH1, and SNQ2 and therefore increased fluconazole efflux. However, the regulation of Pdr1 is poorly understood. In order to identify genes that interact with the Pdr1 transcriptional pathway and influence the susceptibility of C. glabrata to fluconazole, we screened a collection of deletion mutants for those exhibiting increased resistance to fluconazole. Deletion of the gene coding for a protein homologous to the Saccharomyces cerevisiae J protein Jjj1 resulted in decreased fluconazole susceptibility. We used the SAT1 flipper method to generate independent deletion mutants for JJJ1 in an SDD clinical isolate. Expression of both CDR1 and PDR1 was increased in the absence of JJJ1. In the absence of CDR1 or PDR1, deletion of JJJ1 has only a modest effect on fluconazole susceptibility. Transcriptional profiling using transcriptome sequencing (RNA-seq) revealed upregulation of genes of the Pdr1 regulon in the absence of JJJ1. Jjj1 appears to be a negative regulator of fluconazole resistance in C. glabrata and acts primarily through upregulation of the ABC transporter gene CDR1 via activation of the Pdr1 transcriptional pathway. IMPORTANCECandida glabrata is the second most common species of Candida recovered from patients with invasive candidiasis. The increasing number of infections due to C. glabrata, combined with its high rates of resistance to the commonly used, well-tolerated azole class of antifungal agents, has limited the use of this antifungal class. This has led to the preferential use of echinocandins as empirical treatment for serious Candida infections. The primary mechanism of resistance found in clinical isolates is the presence of an activating mutation in the gene encoding the transcription factor Pdr1 that results in upregulation of one or more of the efflux pumps Cdr1, Pdh1, and Snq2. By developing a better understanding of this mechanism of resistance to the azoles, it will be possible to develop strategies for reclaiming the utility of the azole antifungals against this important fungal pathogen.

Loss of C-5 Sterol Desaturase Activity Results in Increased Resistance to Azole and Echinocandin Antifungals in a Clinical Isolate of Candida parapsilosis.

Among emerging non-albicans Candida species, Candida parapsilosis is of particular concern as a cause of nosocomial bloodstream infections in neonatal and intensive care unit patients. While fluconazole and echinocandins are considered effective treatments for such infections, recent reports of fluconazole and echinocandin resistance in C. parapsilosis indicate a growing problem. The present study describes a novel mechanism of antifungal resistance in this organism affecting susceptibility to azole and echinocandin antifungals in a clinical isolate obtained from a patient with prosthetic valve endocarditis. Transcriptome analysis indicated differential expression of several genes in the resistant isolate, including upregulation of ergosterol biosynthesis pathway genes ERG2, ERG5, ERG6, ERG11, ERG24, ERG25, and UPC2 Whole-genome sequencing revealed that the resistant isolate possessed an ERG3 mutation resulting in a G111R amino acid substitution. Sterol profiles indicated a reduction in sterol desaturase activity as a result of this mutation. Replacement of both mutant alleles in the resistant isolate with the susceptible isolate's allele restored wild-type susceptibility to all azoles and echinocandins tested. Disruption of ERG3 in the susceptible and resistant isolates resulted in a loss of sterol desaturase activity, high-level azole resistance, and an echinocandin-intermediate to -resistant phenotype. While disruption of ERG3 in C. albicans resulted in azole resistance, echinocandin MICs, while elevated, remained within the susceptible range. This work demonstrates that the G111R substitution in Erg3 is wholly responsible for the altered azole and echinocandin susceptibilities observed in this C. parapsilosis isolate and is the first report of an ERG3 mutation influencing susceptibility to the echinocandins.

Azole Resistance in Candida glabrata.

Candida infections have increased due to the growth and expansion of susceptible patient populations. The azole fluconazole is the most widely prescribed antifungal, but rising rates of clinical resistance among Candida glabrata isolates have greatly limited its utility. A better understanding of the mechanisms of azole antifungal resistance will provide information needed to overcome this clinical problem and reclaim this antifungal class as an option for empiric treatment of Candida infections. By far, the most frequent mechanism of azole resistance in C. glabrata is the overexpression of multidrug transporters due to activating mutations in the gene encoding transcription factor Pdr1. In this review, we will discuss the molecular and genetic basis of azole resistance in C. glabrata with particular attention given to the most recent discoveries in this field.

The RTA3 Gene, Encoding a Putative Lipid Translocase, Influences the Susceptibility of Candida albicans to Fluconazole.

The RTA3 gene, coding for a member of the Rta1p-like lipid-translocating exporter family, is coordinately upregulated with the ATP-binding cassette transporter genes CDR1 and CDR2 in azole-resistant clinical isolates of Candida albicans that carry activating mutations in the transcription factor Tac1p. We show here that deleting RTA3 in an azole-resistant clinical isolate carrying a Tac1p-activating mutation lowered fluconazole resistance by 2-fold, while overexpressing RTA3 in an azole-susceptible clinical isolate resulted in enhanced fluconazole tolerance associated with trailing growth in a liquid microtiter plate assay. We also demonstrate that an Rta3p-green fluorescent protein (GFP) fusion protein localizes predominantly to the plasma membrane, consistent with a putative function for Rta3p as a lipid translocase.

Reduction in Cell Viability and in Homeobox Protein Levels Following in Vitro Exposure to δ-tocopherol in Acute Myeloid Leukemia.

δ-Tocopherol (δ-T), the least prevalent tocopherol in our diet, was described to have a more potent anticancer activity in solid tumors compared to the other tocopherols. δ-T induces tumor cell death through peroxisome proliferator-activated receptor γ (PPAR-γ) induction, cyclin-D1 inhibition, and modulation of redox balance. Nevertheless, the role of δ-T in preventing or treating hematologic malignancies has not been studied. In this study, we screened the efficacy of δ-T against six cell lines representing a wide spectrum of hematologic malignancies: Jurkat (acute T-cell leukemia), K-562 (chronic myeloid leukemia), KG-1 [acute myeloid leukemia (AML)], THP-1 (acute monocytic leukemia), TOM-1 (acute lymphoblastic leukemia), and UMCL01-101 (AIDS-associated diffuse large B-cell lymphoma). Interestingly, the AML cell line KG-1 was the only one to be significantly affected at concentrations of δ-T as low as 20 µM. The antileukemic activity of δ-T in AML was verified in a set of primary cells collected from patients newly diagnosed with AML. Apoptotic induction and cell cycle arrest explained the efficacy of δ-T against KG-1 cells. The mechanism of cell growth inhibition of δ-T was through downregulation of cyclin-D1 and a set of homeobox proteins (HOXA9, PBX1, and Cdx2) that have a well-documented role in the pathobiology of AML.

Azole Antifungal Resistance in Candida albicans and Emerging Non-albicans Candida Species.

Within the limited antifungal armamentarium, the azole antifungals are the most frequent class used to treat Candida infections. Azole antifungals such as fluconazole are often preferred treatment for many Candida infections as they are inexpensive, exhibit limited toxicity, and are available for oral administration. There is, however, extensive documentation of intrinsic and developed resistance to azole antifungals among several Candida species. As the frequency of azole resistant Candida isolates in the clinical setting increases, it is essential to elucidate the mechanisms of such resistance in order to both preserve and improve upon the azole class of antifungals for the treatment of Candida infections. This review examines azole resistance in infections caused by C. albicans as well as the emerging non-albicans Candida species C. parapsilosis, C. tropicalis, C. krusei, and C. glabrata and in particular, describes the current understanding of molecular basis of azole resistance in these fungal species.

Contribution of clinically derived mutations in ERG11 to azole resistance in Candida albicans.

In Candida albicans, the ERG11 gene encodes lanosterol demethylase, the target of the azole antifungals. Mutations in ERG11 that result in an amino acid substitution alter the abilities of the azoles to bind to and inhibit Erg11, resulting in resistance. Although ERG11 mutations have been observed in clinical isolates, the specific contributions of individual ERG11 mutations to azole resistance in C. albicans have not been widely explored. We sequenced ERG11 in 63 fluconazole (FLC)-resistant clinical isolates. Fifty-five isolates carried at least one mutation in ERG11, and we observed 26 distinct positions in which amino acid substitutions occurred. We mapped the 26 distinct variant positions in these alleles to four regions in the predicted structure for Erg11, including its predicted catalytic site, extended fungus-specific external loop, proximal surface, and proximal surface-to-heme region. In total, 31 distinct ERG11 alleles were recovered, with 10 ERG11 alleles containing a single amino acid substitution. We then characterized 19 distinct ERG11 alleles by introducing them into the wild-type azole-susceptible C. albicans SC5314 strain and testing them for susceptibilities to FLC, itraconazole (ITC), and voriconazole (VRC). The strains that were homozygous for the single amino acid substitutions Y132F, K143R, F145L, S405F, D446E, G448E, F449V, G450E, and G464S had a ≥ 4-fold increase in FLC MIC. The strains that were homozygous for several double amino acid substitutions had decreased azole susceptibilities beyond those conferred by any single amino acid substitution. These findings indicate that mutations in ERG11 are prevalent among azole-resistant clinical isolates and that most mutations result in appreciable changes in FLC and VRC susceptibilities.

UPC2A is required for high-level azole antifungal resistance in Candida glabrata.

Candida glabrata, the second most common cause of Candida infections, is associated with high rates of mortality and often exhibits resistance to the azole class of antifungal agents. Upc2 and Ecm22 in Saccharomyces cerevisiae and Upc2 in Candida albicans are the transcriptional regulators of ERG11, the gene encoding the target of azoles in the ergosterol biosynthesis pathway. Recently two homologs for these transcription factors, UPC2A and UPC2B, were identified in C. glabrata. One of these, UPC2A, was shown to influence azole susceptibility. We hypothesized that due to the global role for Upc2 in sterol biosynthesis in S. cerevisiae and C. albicans, disruption of UPC2A would enhance the activity of fluconazole in both azole-susceptible dose-dependent (SDD) and -resistant C. glabrata clinical isolates. To test this hypothesis, we constructed mutants with disruptions in UPC2A and UPC2B alone and in combination in a matched pair of clinical azole-SDD and -resistant isolates. Disruption of UPC2A in both the SDD and resistant isolates resulted in increased susceptibility to sterol biosynthesis inhibitors, including a reduction in fluconazole MIC and minimum fungicidal concentration, enhanced azole activity by time-kill analysis, a decrease in ergosterol content, and downregulation of baseline and inducible expression of several sterol biosynthesis genes. Our results indicate that Upc2A is a key regulator of ergosterol biosynthesis and is essential for resistance to sterol biosynthesis inhibitors in C. glabrata. Therefore, the UPC2A pathway may represent a potential cotherapeutic target for enhancing azole activity against this organism.

γ-Tocotrienol induces growth arrest through a novel pathway with TGFß2 in prostate cancer.

Regions along the Mediterranean and in southern Asia have lower prostate cancer incidence compared to the rest of the world. It has been hypothesized that one of the potential contributing factors for this low incidence includes a higher intake of tocotrienols. Here we examine the potential of γ-tocotrienol (GT3) to reduce prostate cancer proliferation and focus on elucidating pathways by which GT3 could exert a growth-inhibitory effect on prostate cancer cells. We find that the γ and δ isoforms of tocotrienol are more effective at inhibiting the growth of prostate cancer cell lines (PC-3 and LNCaP) compared with the γ and δ forms of tocopherol. Knockout of PPAR-γ and GT3 treatment show inhibition of prostate cancer cell growth, through a partially PPAR-γ-dependent mechanism. GT3 treatment increases the levels of the 15-lipoxygenase-2 enzyme, which is responsible for the conversion of arachidonic acid to the PPAR-γ-activating ligand 15-S-hydroxyeicosatrienoic acid. In addition, the latent precursor and the mature forms of TGFß2 are down-regulated after treatment with GT3, with concomitant disruptions in TGFß receptor I, SMAD-2, p38, and NF-κB signaling.

Gamma tocopherol upregulates the expression of 15-S-HETE and induces growth arrest through a PPAR gamma-dependent mechanism in PC-3 human prostate cancer cells.

Chronic inflammation and dietary fat consumption correlates with an increase in prostate cancer. Our previous studies in the colon have demonstrated that gamma-tocopherol treatment could upregulate the expression of peroxisome proliferator-activated preceptors (PPAR) gamma, a nuclear receptor involved in fatty acid metabolism as well modulation of cell proliferation and differentiation. In this study, we explored the possibility that gamma-tocopherol could induce growth arrest in PC-3 prostate cancer cells through the regulation of fatty acid metabolism. Growth arrest (40%) and PPAR gamma mRNA and protein upregulation was achieved with gamma-tocopherol within 6 h. gamma-Tocopherol-mediated growth arrest was demonstrated to be PPAR gamma dependent using the agonist GW9662 and a PPAR gamma dominant negative vector. gamma-tocopherol was shown not to be a direct PPAR gamma ligand, but rather 15-S-HETE (an endogenous PPAR gamma ligand) was upregulated by gamma-tocopherol treatment. 15-Lipoxygenase-2, a tumor suppressor and the enzyme that converts arachidonic acid to 15-S-HETE, was upregulated at 3 h following gamma-tocopherol treatment. Expression of proteins downstream of the PPAR gamma pathway were examined. Cyclin D1, cyclin D3, bcl-2, and NFkappa B proteins were found to be downregulated following gamma-tocopherol treatment. These data demonstrate that the growth arrest mediated by gamma-tocopherol follows a PPAR-gamma-dependent mechanism.

Morphine promotes Jurkat cell apoptosis through pro-apoptotic FADD/P53 and anti-apoptotic PI3K/Akt/NF-kappaB pathways.

Opiates have been shown to inhibit cell growth and trigger apoptosis, but the underlying molecular mechanisms remain unclear. We have previously shown that morphine induces Fas expression and promotes Fas-mediated apoptosis. Here, we investigated the mechanisms by which morphine modulates apoptosis in human Jurkat cells. Morphine-induced apoptosis was inhibited by transfection with a dominant negative Fas-associated death domain (FADD) plasmid, revealing that morphine-induced apoptosis is dependent on FADD. Furthermore, suppression of endogenous p53 expression by RNA interference technology considerably attenuated the morphine-induced apoptosis. In addition, morphine-induced apoptosis seems to be dependent on the activation of phosphatidylinositol 3-kinase (PI3K), as PI3K inhibition by the PI3K inhibitor LY294002 significantly enhanced morphine-induced apoptosis. Moreover, inhibition of Akt or nuclear factor-kappaB (NF-kappaB) expression by RNA interference technology also dramatically increased morphine-induced apoptosis. Our study thus demonstrates that morphine induces Jurkat cell apoptosis through FADD/p53, anti-apoptotic PI3K/Akt and NF-kappaB pathways.