Forgotten memory storage and retrieval in Drosophila

Inaccessibility of stored memory in ensemble cells through the forgetting process causes animals to be unable to respond to natural recalling cues. While accumulating evidence has demonstrated that reactivating memory-stored cells can switch cells from an inaccessible state to an accessible form and lead to recall of previously learned information, the underlying cellular and molecular mechanisms remain elusive. The current study used Drosophila as a model to demonstrate that the memory of one-trial aversive olfactory conditioning, although inaccessible within a few hours after learning, is stored in KCαβ and retrievable after mild retraining. One-trial aversive conditioning triggers protein synthesis to form a long-lasting cellular memory trace, approximately 20 days, via creb in KCαβ, and a transient cellular memory trace, approximately one day, via orb in MBON-α3. PPL1-α3 negatively regulates forgotten one-trial conditioning memory retrieval. The current study demonstrated that KCαβ, PPL1-α3, and MBON-α3 collaboratively regulate the formation of forgotten one-cycle aversive conditioning memory formation and retrieval.

Effects of Accumulated Energy on Nanoparticle Formation in Pulsed-Laser Dewetting of AgCu Thin Films

Ag₅₀Cu₅₀ films were deposited on glass substrates by a sputtering system. Effects of accumulated energy on nanoparticle formation in pulse-laser dewetting of AgCu films were investigated. The results showed that the properties of the dewetted films were found to be dependent on the magnitude of the energy accumulated in the film. For a low energy accumulation, the two distinct nanoparticles had rice-shaped/Ag₆₀Cu₄₀ and hemispherical/Ag₈₀Cu₂₀. Moreover, the absorption spectra contained two peaks at 700 nm and 500 nm, respectively. By contrast, for a high energy accumulation, the nanoparticles had a consistent composition of Ag₆₀Cu₄₀, a mean diameter of 100 nm and a peak absorption wavelength of 550 nm. Overall, the results suggest that a higher Ag content of the induced nanoparticles causes a blue shift of the absorption spectrum, while a smaller particle size induces a red shift.

Crystalline characteristics of annealed AlN films by pulsed laser treatment for solidly mounted resonator applications

AlN films were deposited on Si substrates using a reactive RF magnetron sputtering process and then the films were annealed by using different laser powers and wavelengths (355 nm, 532 nm and 1064 nm). For all three laser systems, the (002) peak intensity was obviously improved following laser irradiation. The improvement in the crystalline property was particularly obtained in the AlN film processed at 355 nm. In particular, given the use of the optimal laser power (0.025 W), the (002) peak intensity was 58.7% higher than that of the as-deposited film. The resonant frequency and 3 dB bandwidth of a SMR filter with an unprocessed AlN film were found to be 2850 MHz and 227.81 MHz, respectively. Following laser treatment with a wavelength of 1064 nm and a power of 0.25 W, the resonant frequency changed from 2850 to 2858 MHz. Moreover, 3 dB bandwidth changed from 227.81 to 202.49 MHz and the return loss of the filter reduced from 17.28 to 16.48 dB. Overall, the results thus show that the frequency response of the SMR filter can be adjusted and the return loss reduced by means of laser treatment with an appropriate wavelength.

Effects of Laser Annealing Parameters on Optical and Electrical Properties of ITO/Metallic Glass Alloy Bi-layer Films

AgAlMg (AAM) films with three different atomic percentage compositions are prepared, namely, Ag12Al62Mg26 (denoted as A1AM), Ag22Al46Mg32 (denoted as A2AM), and Ag36Al25Mg39 (denoted as A3AM). In addition, the AAM films are deposited with four different thicknesses, i.e., 3, 6, 9, and 12 nm. The indium-tin oxide thickness is assigned a constant value of 30 nm in every case. The results show that the optical transmittance of the AAM/IAAM films improves (i.e., increases) with a reducing AAM film thickness, while the electrical resistivity improves (i.e., reduces) with an increasing film thickness. It is shown that the IA2AM film with an AMM thickness of 9 nm yields the optimal compromise between the optical transmittance and the electrical resistivity. The as-deposited IAAM films are found to have optical transmittance and electric resistivity values of 65 % and 90 Ω/□, respectively. The IA2AM films are annealed using a near-infrared laser at different pulse energies with a wavelength of 1064 nm and repetition rates ranging from 100 ~ 400 kHz. For both films, the optical and electrical properties are enhanced as the pulse energy increases to a certain critical value due to a transition from an amorphous microstructure to a crystalline structure. Given a repetition rate of 400 kHz and a pulse energy of 1.03 μJ, the optical transmittance and sheet resistance of the IAAM film are found to be 80 % and 15 Ω/□, respectively. The corresponding value of the Haacke figure of merit changed from 0.15 × 10(-3) to 7.16 × 10(-3) Ω(-1) due to the optimal laser annealing conditions.

A high-resolution computed tomography-based scoring system to differentiate the most infectious active pulmonary tuberculosis from community-acquired pneumonia in elderly and non-elderly patients

OBJECTIVE

The objective of this study was to use high-resolution computed tomography (HRCT) imaging to predict the presence of smear-positive active pulmonary tuberculosis (PTB) in elderly (at least 65 years of age) and non-elderly patients (18-65 years of age).

METHODS

Patients with active pulmonary infections seen from November 2010 through December 2011 received HRCT chest imaging, sputum smears for acid-fast bacilli and sputum cultures for Mycobacterium tuberculosis. Smear-positive PTB was defined as at least one positive sputum smear and a positive culture for M. tuberculosis. Multivariate logistic regression analyses were performed to determine the HRCT predictors of smear-positive active PTB, and a prediction score was developed on the basis of receiver operating characteristic curve analysis.

RESULTS

Of 1,255 patients included, 139 were diagnosed with smear-positive active PTB. According to ROC curve analysis, the sensitivity, specificity, positive predictive value, negative predictive value, false positive rates and false negative rates were 98.6 %, 95.8 %, 78.5 %, 99.8 %, 4.2 % and 1.4 %, respectively, for diagnosing smear-positive active PTB in elderly patients, and 100.0 %, 96.9 %, 76.5 %, 100.0 %, 3.1 % and 0.0 %, respectively, for non-elderly patients.

CONCLUSIONS

HRCT can assist in the early diagnosis of the most infectious active PTB, thereby preventing transmission and minimizing unnecessary immediate respiratory isolation.

KEY POINTS

• HRCT can assist in the early diagnosis of the infectious active PTB • HRCT imaging is useful to predict the presence of smear-positive active PTB • Predictions from the HRCT imaging are valid even before sputum smear or culture results.

Heparin protects BALB/c mice from mite-induced airway allergic inflammation

More and more studies have demonstrated the anti-inflammatory effects of heparin. However, in the aspect of allergic airway inflammation, data about its daily use in animal model is scarce. To evaluate the efficacy of 22-day intranasal heparin administration in mite-induced airway allergic inflammation in BALB/c mice, the murine model of house dust-mite allergen-induced asthma was used to assess the effect of heparin (h) and low molecular weight heparin (l mwh) administered intra-nasally (IN) throughout the full study period (22 days). Effects were monitored by histopathology, cell counts in broncho-alveolar lavage fluid (BALF), local cytokine production, serum, specific antibody levels, and airway resistance measurements. Compared to the positive control group, both hIN and lmwhIN groups had lower peri-bronchiolar/alveolar inflammatory pathology score and lower goblet cell scores (p less than 0.01); lower eosinophil and neutrophil counts in BALF (p less than 0.0001); and lower cytokine levels including IL-17A/F, IL-5, IL-13, IL-8 and eotaxin in lung tissue (p less than 0.001). Serum Der p-specific IgE level was also lower in heparin-treated groups (p less than 0.004). The two heparin-treated groups also revealed lower value of Penh after Mch stimulation. In conclusion, heparin and lmw heparin decrease serum Der p-specific IgE level and possess anti-inflammatory effects on mite-induced airway allergic inflammation model in BALB/c mice.

The use of tissue engineering and stem cells in bladder regeneration

Tissue engineering techniques for bladder regeneration have been applied successfully for many years in a variety of in vitro and in vivo models. But despite these rapid advances, to date, none of the tissue-engineered constructs could be used in human models due to inconsistent results of the described techniques in animal models. Three factors have been identified to influence the regeneration process: identification of the ideal scaffold, appropriate cell population for seeding and the optimal regeneration conditions necessary. Identifying the role of each component will help to unlock the complex regeneration mechanisms required to achieve consistent, reliable results that will allow transition of the technology into clinical practice. This review will discuss the role and applicability of the each factor and provide a future prospective on tissue engineering techniques for bladder regeneration.

Decreased expression of smooth muscle alpha-actin results in decreased contractile function of the mouse bladder

PURPOSE

Smooth muscle alpha-actin (SMalphaA) is an important actin isoform for functional contractility in the mouse bladder. Alterations in the expression of SMalphaA have been associated with a variety of bladder pathological conditions. Recently, a SMalphaA-null mouse was generated and differences in vascular tone and contractility were observed between wild-type and SMalphaA-null mice suggesting alterations in function of vascular smooth muscle. We used SMalphaA-null mice to explore the hypothesis that SMalphaA is necessary for normal bladder function.

MATERIALS AND METHODS

Reverse transcriptase polymerase chain reaction, Western blotting and immunohistochemical staining were used to confirm the absence of SMalphaA transcript and protein in the bladder of SMalphaA-null mice. In vitro bladder contractility compared between bladder rings harvested from wild-type and SMalphaA-null mice was determined by force measurement following electrical field stimulation (EFS), and exposure to chemical agonists and antagonists including KCl, carbachol, atropine and tetrodotoxin. Resulting force generation profiles for each tissue and agent were analyzed.

RESULTS

There was no detectable SMalphaA transcript and protein expression in the bladder of SMalphaA-null mice. Nine wild-type and 9 SMalphaA-null mice were used in the contractility study. Bladders from SMalphaA-null mice generated significantly less force than wild-type mice in response to EFS after KCl. Similarly, bladders from SMalphaA-null mice generated less force than wild-type mice in response to pretreatment EFS, and EFS after carbachol and atropine, although the difference was not significant. Surprisingly, the bladders in SMalphaA-null mice appeared to function normally and showed no gross or histological abnormalities.

CONCLUSIONS

SMalphaA appears to be necessary for the bladder to be able to generate normal levels of contractile force. No functional deficits were observed in the bladders of these animals but no stress was placed on these bladders. To our knowledge this study represents the first report to demonstrate the importance of expression of SMalphaA in force generation in the bladder.

Laparoscopic mid sagittal hemicystectomy and bladder reconstruction with small intestinal submucosa and reimplantation of ureter into small intestinal submucosa: 1-year followup

PURPOSE

We evaluated the long-term results of laparoscopic hemicystectomy and bladder replacement with small intestinal submucosa (SIS) with ureteral reimplantation into the SIS material.

MATERIALS AND METHODS

A total of 12 minipigs underwent laparoscopic hemicystectomy. Six pigs underwent bladder reconstruction with SIS and ipsilateral ureteral reimplantation. The remaining 6 control pigs underwent hemicystectomy and primary bladder closure with ipsilateral nephroureterectomy. Preoperative and followup evaluations included blood chemistry, radiography and urodynamic evaluations. The 6, 3, 6 and 9-week, and 12-month followup evaluations included biopsies. At 1 year the animals were sacrificed. Histopathological and contractility studies, and reverse transcriptase-polymerase chain reaction for growth factors and basement membrane components were performed.

RESULTS

Bladder capacity and bladder compliance were similar in the 2 groups at all time points. One pig per group died, that is a control at the 9-month evaluation due to an anesthetic complication and an SIS pig 7 months after bladder reconstruction due to spontaneous bladder rupture at the anastomotic site. In the SIS group 4 of 5 surviving pigs had unobstructed reimplanted ureters without evidence of hydroureteronephrosis, while 1 had high grade obstruction at the reimplantation site. Histopathology study after 1 year revealed muscle at the graft periphery and center but it consisted of small fused bundles with significant fibrosis. Nerves were present at the graft periphery and center but they were decreased in number.

CONCLUSIONS

Laparoscopic SIS bladder reconstruction and ureteral reimplantation into the SIS after hemicystectomy are technically feasible. However, compared to primary bladder closure no advantage in bladder capacity or compliance was documented.

Molecular cloning and expression of woodchuck granulocyte-macrophage colony stimulating factor

Granulocyte-macrophage colony stimulating factor (GM-CSF) has immunoregulatory and antiviral effects, and may thus be promising for the treatment of chronic hepatitis B. Using woodchuck hepatitis virus (WHV)-infected woodchuck as an animal model to test the efficacy and safety of GM-CSF on the therapy of chronic hepatitis B, woodchuck GM-CSF will be required due to the apparent species-specific activity of GM-CSF. The cDNA of woodchuck GM-CSF was cloned using reverse transcription-polymerase chain reaction (RT-PCR) with primers deriving from highly conserved regions of GM-CSF genes from other species. The deduced amino acids, including the signal peptide, is 138 in length and its identities to human, murine, canine and bovine GM-CSFs are 63, 49, 63, and 63% respectively. The genomic DNA of woodchuck GM-CSF was also cloned by PCR. Its organization is highly homologous to that of human and murine GM-CSF genes, consisting of four exons and three introns. Cloned woodchuck GM-CSF was expressed transiently in 293T cells. The recombinant protein expressed was found to stimulate the growth and differentiation of woodchuck bone marrow cells, indicating the protein expressed by the cloned gene is functional. These results pave the way for future studies on the potential role of GM-CSF for the treatment of chronic hepatitis B by using this animal model.

Copper(II) complexes with N,N'-dialkyl-1,10-phenanthroline-2,9-dimethanamine: synthesis, characterization, DNA-binding thermodynamical and kinetic studies

Copper(II) complexes (Cu-L, L=N,N'-dialkyl-1,10-phenanthroline-2,9-dimethanamine) were synthesized and characterized by elemental analyses, IR spectra and conductance measurement. The interaction of the copper(II) complex with calf thymus DNA was studied by means of UV melting experiments, fluorescence spectra and circular dichroic spectra. Using ethidium bromide as a fluorescence probe, the binding mode of the complexes Cu-L with calf-thymus DNA was studied spectroscopically. The results indicate that the complexes Cu-L perhaps interact with calf-thymus DNA by both intercalative and covalent binding. Kinetics of binding of the cupric complexes to DNA was studied for the first time using ethidium bromide as a fluorescence probe with stopped-flow spectrophotometer under pseudo-first-order condition. The stronger binding of two steps in the process of the complexes Cu-L interacting with DNA was observed, and the probable interaction process was discussed in detail. The corresponding k(obs) and E(a) of binding to DNA (where k(obs) is the observed pseudo-first-order rate constant, E(a) is the observed energy of activation) were obtained.

Akt suppresses androgen-induced apoptosis by phosphorylating and inhibiting androgen receptor

Whereas several apoptosis-related proteins have been linked to the antiapoptotic effects of Akt serine-threonine kinase, the search continues to explain the Akt signaling role in promoting cell survival via antiapoptotic effects. Here, we demonstrate that Akt phosphorylates the androgen receptor (AR) at Ser-210 and Ser-790. A mutation at AR Ser-210 results in the reversal of Akt-mediated suppression of AR transactivation. Activation of the phosphatidylinositol-3-OH kinase/Akt pathway results in the suppression of AR target genes, such as p21, and the decrease of androgen/AR-mediated apoptosis, which may involve the inhibition of interaction between AR and AR coregulators. Together, these findings provide a molecular basis for cross-talk between two signaling pathways at the level of Akt and AR-AR coregulators that may help us to better understand the roles of Akt in the androgen/AR-mediated apoptosis.

Focus measurement with a simple pattern design

The increasingly smaller depth of focus of advanced lithographic tools requires that the position of best focus be determined to ensure accuracy and efficiency. We present what we believe is a novel bar in bar that is drawn on a conventional chrome binary mask to translate focal errors into center-to-center shifts of outer and inner bars. An overlay measurement tool can easily measure this shift. A symmetrical center-to-center shift against best focus is created during defocus, and this shift can be well fitted by a second-order polynomial equation. Simply differentiating the fitted equation leads to an accurate and reliable focus value, with a maximum error of less than 0.05 microm. The proposed technique can also be employed to evaluate the tilt, field curvature, and astigmatism of advanced lithographic tools.

From transforming growth factor-beta signaling to androgen action: identification of Smad3 as an androgen receptor coregulator in prostate cancer cells

Although transforming growth factor-beta (TGF-beta) has been identified to mainly inhibit cell growth, the correlation of elevated TGF-beta with increasing serum prostate-specific antigen (PSA) levels in metastatic stages of prostate cancer has also been well documented. The molecular mechanism for these two contrasting effects of TGF-beta, however, remains unclear. Here we report that Smad3, a downstream mediator of the TGF-beta signaling pathway, functions as a coregulator to enhance androgen receptor (AR)-mediated transactivation. Compared with the wild-type AR, Smad3 acts as a strong coregulator in the presence of 1 nM 5alpha-dihydrotestosterone, 10 nM 17beta-estradiol, or 1 microM hydroxyflutamide for the LNCaP mutant AR (mtAR T877A), found in many prostate tumor patients. We further showed that endogenous PSA expression in LNCaP cells can be induced by 5alpha-dihydrotestosterone, and the addition of the Smad3 further induces PSA expression. Together, our findings establish Smad3 as an important coregulator for the androgen-signaling pathway and provide a possible explanation for the positive role of TGF-beta in androgen-promoted prostate cancer growth.

Structure-function aspects and inhibitor design of type 5 17beta-hydroxysteroid dehydrogenase (AKR1C3)

17beta-Hydroxysteroid dehydrogenase (17beta-HSD) type 5 has been cloned from human prostate and is identical to type 2 3alpha-HSD and is a member of the aldo-keto reductase (AKR) superfamily; it is formally AKR1C3. In vitro the homogeneous recombinant enzyme expressed in Escherichia coli functions as a 3-keto-, 17-keto- and 20-ketosteroid reductase and as a 3alpha-, 17beta- and 20alpha-hydroxysteroid oxidase. The enzyme will reduce 5alpha-DHT, Delta(4)-androstene-3,17-dione, estrone and progesterone to produce 3alpha-androstanediol, testosterone, 17beta-estradiol and 20alpha-hydroxprogesterone, respectively. It will also oxidize 3alpha-androstanediol, testosterone, 17beta-estradiol and 20alpha-hydroxyprogesterone to produce 5alpha-androstane-3,17-dione, Delta(4)-androstene-3,17-dione, and progesterone, respectively. Many of these properties are shared by the related AKR1C1, AKR1C2 and AKR1C4 isoforms. RT-PCR shows that AKR1C3 is dominantly expressed in the human prostate and mammary gland. Examination of k(cat)/K(m) for these reactions indicates that as a reductase it prefers 5alpha-dihydrotestosterone and 5alpha-androstane-3,17-dione as substrates to Delta(4)-androstene-3,17-dione, suggesting that in the prostate it favors the formation of inactive androgens. Its concerted reductase activity may, however, lead to a pro-estrogenic state in the breast since it will convert estrone to 17beta-estradiol; convert Delta(4)-androstene-3,17-dione to testosterone (which can be aromatized to 17beta-estradiol); and it will reduce progesterone to its inactive metabolite 20alpha-hydroxyprogesterone. Drawing on detailed structure-function analysis of the related rat 3alpha-HSD (AKR1C9), which shares 69% sequence identity with AKR1C3, it is predicted that AKR1C3 catalyzes an ordered bi bi mechanism, that the rate determining step is k(chem), and that an oxyanion prevails in the transition state. Based on these relationships steroidal-based inhibitors that compete with the steroid product would be desirable since they would act as uncompetitive inhibitors. With regards to transition state analogs steroid carboxylates and pyrazoles may be preferred while 3alpha, 17beta or 20alpha-spiro-oxiranes may act as mechanism-based inactivators.

Synthesis, characterization and cytotoxicity of lanthanum(III) complexes with novel 1,10-phenanthroline-2,9-bis-alpha-amino acid conjugates

Eight lanthanum(III) complexes with novel 1,10-phenanthroline-2,9-bis-alpha-amino acid conjugates were synthesized and characterized by elemental analyses, IR, MS, 1H-NMR, thermal analysis and conductance measurement. All lanthanum(III) complexes and the corresponding soluble ligand in water have been assayed for antitumor activity in vitro against HL-60 (human leukocytoma) cells, HCT-8 (human coloadenocarcinoma) cells, BGC-823 (human stomach carcinoma) cells, BeL-7402 (human liver carcinoma) cells and KB (human nasopharyngeal carcinoma) cells. The results show that several complexes have relative activity against different cell lines. In particular, the complexes La(L2) and La(L5) show relatively high activity against the BeL-7402 cell line. Moreover, they are slightly more effective than cisplatin. DNA binding studies indicate that the complex La(L2) possibly interacts with calf thymus DNA by both intercalative and covalent binding.

Increase of androgen-induced cell death and androgen receptor transactivation by BRCA1 in prostate cancer cells

Although mutations of the breast cancer susceptibility gene 1 (BRCA1) may play important roles in breast and prostate cancers, the detailed mechanism linking the functions of BRCA1 to these two hormone-related tumors remains to be elucidated. Here, we report that BRCA1 interacts with androgen receptor (AR) and enhances AR target genes, such as p21((WAF1/CIP1)), that may result in the increase of androgen-induced cell death in prostate cancer cells. The BRCA1-enhanced AR transactivation can be further induced synergistically with AR coregulators, such as CBP, ARA55, and ARA70. Together, these data suggest that the BRCA1 may function as an AR coregulator and play positive roles in androgen-induced cell death in prostate cancer cells and other androgen/AR target organs.

Human 3alpha-hydroxysteroid dehydrogenase isoforms (AKR1C1-AKR1C4) of the aldo-keto reductase superfamily: functional plasticity and tissue distribution reveals roles in the inactivation and formation of male and female sex hormones

The kinetic parameters, steroid substrate specificity and identities of reaction products were determined for four homogeneous recombinant human 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) isoforms of the aldo-keto reductase (AKR) superfamily. The enzymes correspond to type 1 3alpha-HSD (AKR1C4), type 2 3alpha(17beta)-HSD (AKR1C3), type 3 3alpha-HSD (AKR1C2) and 20alpha(3alpha)-HSD (AKR1C1), and share at least 84% amino acid sequence identity. All enzymes acted as NAD(P)(H)-dependent 3-, 17- and 20-ketosteroid reductases and as 3alpha-, 17beta- and 20alpha-hydroxysteroid oxidases. The functional plasticity of these isoforms highlights their ability to modulate the levels of active androgens, oestrogens and progestins. Salient features were that AKR1C4 was the most catalytically efficient, with k(cat)/K(m) values for substrates that exceeded those obtained with other isoforms by 10-30-fold. In the reduction direction, all isoforms inactivated 5alpha-dihydrotestosterone (17beta-hydroxy-5alpha-androstan-3-one; 5alpha-DHT) to yield 5alpha-androstane-3alpha,17beta-diol (3alpha-androstanediol). However, only AKR1C3 reduced Delta(4)-androstene-3,17-dione to produce significant amounts of testosterone. All isoforms reduced oestrone to 17beta-oestradiol, and progesterone to 20alpha-hydroxy-pregn-4-ene-3,20-dione (20alpha-hydroxyprogesterone). In the oxidation direction, only AKR1C2 converted 3alpha-androstanediol to the active hormone 5alpha-DHT. AKR1C3 and AKR1C4 oxidized testosterone to Delta(4)-androstene-3,17-dione. All isoforms oxidized 17beta-oestradiol to oestrone, and 20alpha-hydroxyprogesterone to progesterone. Discrete tissue distribution of these AKR1C enzymes was observed using isoform-specific reverse transcriptase-PCR. AKR1C4 was virtually liver-specific and its high k(cat)/K(m) allows this enzyme to form 5alpha/5beta-tetrahydrosteroids robustly. AKR1C3 was most prominent in the prostate and mammary glands. The ability of AKR1C3 to interconvert testosterone with Delta(4)-androstene-3,17-dione, but to inactivate 5alpha-DHT, is consistent with this enzyme eliminating active androgens from the prostate. In the mammary gland, AKR1C3 will convert Delta(4)-androstene-3,17-dione to testosterone (a substrate aromatizable to 17beta-oestradiol), oestrone to 17beta-oestradiol, and progesterone to 20alpha-hydroxyprogesterone, and this concerted reductive activity may yield a pro-oesterogenic state. AKR1C3 is also the dominant form in the uterus and is responsible for the synthesis of 3alpha-androstanediol which has been implicated as a parturition hormone. The major isoforms in the brain, capable of synthesizing anxiolytic steroids, are AKR1C1 and AKR1C2. These studies are in stark contrast with those in rat where only a single AKR with positional- and stereo-specificity for 3alpha-hydroxysteroids exists.

Genomic structure of rat 3alpha-hydroxysteroid/dihydrodiol dehydrogenase (3alpha-HSD/DD, AKR1C9)

Rat liver 3alpha-hydroxysteroid/dihydrodiol dehydrogenase (3alpha-HSD/DD) is a member of the aldo-keto reductase (AKR) superfamily. It is involved in the inactivation of steroid hormones and the metabolic activation of polycyclic aromatic hydrocarbons (PAH) by converting trans-dihydrodiols into reactive and redox-active o-quinones. The structure of the 5'-flanking region of the gene and factors involved in the constitutive and regulated expression of this gene have been reported [H.-K. Lin, T.M. Penning, Cloning, sequencing, and functional analysis of the 5'-flanking region of the rat 3alpha-hydroxysteroid/dihydrodiol dehydrogenase gene, Cancer Res. 55 (1995) 4105-4113]. We now describe the complete genomic structure of the rat type 1 3alpha-HSD/DD gene. Charon 4A and P1 genomic clones contained at least three rat genes (type 1, type 2 and type 3 3alpha-HSD/DD) each of which encoded for the same open reading frame (ORF) but differed in their exon-intron organization. 5'-RACE confirmed that the type 1 3alpha-HSD/DD gene encodes for the dominant transcript in rat liver and it was the regulation of this gene that was previously studied. The rat type 1 3alpha-HSD/DD gene is 30 kb in length and consists of nine exons and eight introns. Exon 9 encodes +931 to 966 bp of the ORF and the 1292 bp 3'-UTR implicated in mRNA stability. This genomic structure is nearly identical to the homologous human genes, type 1 3alpha-HSD (chlordecone reductase/DD4, AKR1C4), type 2 3alpha-HSD (AKR1C3) and type 3 3alpha-HSD (bile-acid binding protein, AKR1C2) genes. Three different cDNA's containing identical ORFs for 3alpha-HSD have been reported suggesting that all three genes may be expressed in rat liver. Using 5' primers corresponding to the 5'-UTR's of the three different cDNA's only one PCR fragment was obtained and corresponded to the type 1 3alpha-HSD/DD gene. These data suggested that the type 2 and type 3 3alpha-HSD/DD genes are not abundantly expressed in rat liver. It is unknown whether the type 2 and type 3 3alpha-HSD/DD genes represent pseudo-genes or whether they represent genes that are differentially expressed in other rat tissues.

Differential induction of androgen receptor transactivation by different androgen receptor coactivators in human prostate cancer DU145 cells

Recently identified androgen receptor (AR) coactivators were used in this study to determine whether the specificity of sex hormones and antiandrogens could be modulated at the coactivator level. We found that ARA70 is the best coactivator to confer the androgenic activity on 17beta-estradiol. Only ARA70 and ARA55 could increase significantly the androgenic activity of hydroxyflutamide, a widely used antiand rogen for the treatment of prostate cancer. None of the AR coactivators we tested could significantly confer androgenic activity on progesterone and glucocorticoid at their physiological concentrations (1-10nM). We also found that ARA70, ARA55, and ARA54, but not steroid receptor coactivator-1 (SRC-1) and Rb, could significantly enhance the delta5-androstenediol-mediated AR transactivation. Furthermore, in comparing the relative specificity of these coactivators to AR in DU145 cells, our results suggested that ARA70 has a relatively higher specificity and that SRC-1 can enhance almost equally well many other steroid receptors. Finally, our data demonstrated that AR itself and some select AR coactivators such as ARA70 or ARA54 could, respectively, interact with CBP and p300/CBP-associated factors that have histone acetyl-transferase activity for assisting chromatin remodeling. Together, our data suggest that the specificity of sex hormones and antiandrogens can be modulated by some selective AR coactivators. These findings may not only help us to better understand the specificity of the sex hormones and antiandrogens, but also facilitate the development of better antiandrogens to fight the androgen-related diseases, such as prostate cancer.

Differential induction of the androgen receptor transcriptional activity by selective androgen receptor coactivators

Several new androgen receptor (AR) cofactors, associated to the ligand binding domain of AR, have been identified by our group and named AR associated protein (ARA)70, ARA55, and ARA54. Our previous reports have suggested that the cofactor ARA70 can confer the androgenic effect from 17 beta-estradiol (E2) and antiandrogen to AR. It is of interest for us to compare and determine if the specificity of sex hormones and antiandrogens could be modulated by different coactivators. Our results indicate that ARA70 is the best coactivator to confer the androgenic activity on E2. Only ARA70 and ARA55 could increase significantly the androgenic activity of hydroxyflutamide, a widely used antiandrogen for the treatment of prostate cancer. Furthermore, as compared to the relative specificity of these coactivators to AR in the prostate cancer DU145 cells, our results suggest that ARA70 has a relatively higher specificity. Together, our data suggest that the specificity of sex hormones and antiandrogens can be modulated by some selective AR coactivators. These findings may not only help us to better understand the specificity of the sex hormones and antiandrogens, but also to facilitate the development of better antiandrogens or androgens to fight the androgen-related diseases, such as prostate cancer.

From HER2/Neu signal cascade to androgen receptor and its coactivators: a novel pathway by induction of androgen target genes through MAP kinase in prostate cancer cells

Overexpression of the HER2/Neu protooncogene has been linked to the progression of breast cancer. Here we demonstrate that the growth of prostate cancer LNCaP cells can also be increased by the stable transfection of HER2/Neu. Using AG879, a HER2/Neu inhibitor, and PD98059, a MAP kinase inhibitor, as well as MAP kinase phosphatase-1 (MPK-1), in the transfection assay, we found that HER2/Neu could induce prostate-specific antigen (PSA), a marker for the progression of prostate cancer, through the MAP kinase pathway at a low androgen level. Reporter assays and mammalian two-hybrid assays further suggest this HER2/Neu-induced androgen receptor (AR) transactivation may function through the promotion of interaction between AR and AR coactivators, such as ARA70. Furthermore, we found this HER2/Neu --> MAP kinase --> AR-ARAs --> PSA pathway could not be blocked completely by hydroxyflutamide, an antiandrogen used in the treatment of prostate cancer. Together, these data provide a novel pathway from HER2/Neu to AR transactivation, and they may represent one of the reasons for the PSA re-elevation and hormone resistance during androgen ablation therapy in prostate cancer patients.

Genetic manipulation to identify limiting steps and develop strategies for high-level expression of penicillin acylase in Escherichia coli

We have identified the bottleneck steps limiting expression of penicillin acylase (PAC) through comparison of the expression performance for various PAC-expression vectors constructed by genetically modulating the efficiencies of transcription and/or translation of the pac gene. To our knowledge, this is the first report demonstrating that expression of PAC could be limited by various steps, such as transcription, translation, and post-translational steps (i.e. translocation and periplasmic processing), depending on the host/vector systems. Results also indicate that the structure of the wild-type pac gene might not be optimal for direct use in production of PAC using recombinant DNA technology. To improve the gene expression, transcription was enhanced by manipulating certain DNA bases in the pac regulatory region, whereas translation was enhanced by enlarging the spacing between the ribosome binding site and the ATG initiation codon to increase the initiation efficiency. The information is useful in terms of developing genetic strategies for overproduction of recombinant PAC in Escherichia coli.

Effect of SecB chaperone on production of periplasmic penicillin acylase in Escherichia coli

The effect of SecB chaperone on production of periplasmic penicillin acylase (PAC) in Escherichia coli was investigated. It appears that formation of PAC required the function of SecB chaperone and the amount of SecB required was at a basal level. The secB mutant was defective in production of PAC, and the impairment could be complemented by extrachromosomally supplementing SecB in trans. The function of SecB might be primarily stabilizing the cytoplasmic PAC precursors. Overproduction of SecB chaperone usually resulted in an increase in the amount of PAC precursors without enhancing PAC activity. In addition, most of the PAC precursors were located in the periplasm, suggesting that formation of active PAC was likely limited by periplasmic processing steps.

Manipulation of carbon assimilation with respect to expression of the pac gene for improving production of penicillin acylase in Escherichia coli

A strategy of genetically manipulating carbon assimilation with respect to expression of the pac gene was employed for overproduction of recombinant penicillin acylase (PAC). Two expression plasmids of pCLL2902 and pCLL3201, which contain the pac coding region but differ in the pac regulatory region, were constructed for the production experiments. Expression of the pac gene was subjected to phenyl acetic acid (PAA-) induction and glucose catabolite repression for pCLL3201, whereas it was subjected to neither of the two transcriptional regulations for pCLL2902. The specific PAC activity for strains harboring pCLL2902 was significantly higher than that for strains harboring pCLL3201 due to an improved transcription efficiency. In addition, no inclusion bodies were observed upon production of PAC using the current expression systems. The results suggest that using the native pac promoter instead of a strong promoter such as tac for regulation is a feasible approach for production of PAC. The impact of the current expression systems is also significant from a process viewpoint since, using strains harboring pCLL2902, not only could glucose replace PAA as a carbon source of Escherichia coli cultures for production of PAC but also the volumetric PAC activity was highly improved.

Isoform-specific induction of a human aldo-keto reductase by polycyclic aromatic hydrocarbons (PAHs), electrophiles, and oxidative stress: implications for the alternative pathway of PAH activation catalyzed by human dihydrodiol dehydrogenase

Human dihydrodiol dehydrogenase (DD) isoforms are aldo-keto reductases (AKRs) that activate polycyclic aromatic hydrocarbons (PAHs) by oxidizing trans-dihydrodiol proximate carcinogens to reactive and redox-active ortho-quinones. Of these, human AKR1C1 (DD1) and AKR1C2 (DD2) oxidize trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene to the cytotoxic and genotoxic metabolite benzo[a]pyrene-7,8-dione (BPQ) with the highest catalytic efficiency. Exposure of HepG2 cells to a panel of inducers revealed that mRNA encoding one or more human AKR1C member(s) was induced (3- to 10-fold) by benzo[a]pyrene and other polycyclic aromatic compounds (bi-functional inducers), electrophilic Michael acceptors and phenolic antioxidants (monofunctional inducers), and reactive oxygen species (ROS). The induction of AKR1C mRNA by bifunctional inducers was delayed with respect to the induction of CYP1A1 mRNA, and AKR1C mRNA was not induced by the nonmetabolizable aryl hydrocarbon receptor ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). These data suggest that, in contrast to the CYPs, induction of AKR1C member(s) by PAHs and other bifunctional inducers is mediated indirectly via an antioxidant response element rather than a xenobiotic response element. Immunoblot and enzymatic assays confirmed that the increases in AKR1C mRNA were faithfully translated into functional AKR1C protein(s). The increased DD activity in HepG2 lysates was inhibited only by high concentrations of ursodeoxycholate, which suggested that AKR1C2 (DD2, bile-acid-binding protein) was not the isoform induced. RNase protection assays identified AKR1C1 (DD1) mRNA as the transcript which was up-regulated by mono- and bi-functional inducers and ROS in both human hepatoma (HepG2) and colon carcinoma (HT29) cells. BPQ, the electrophilic and redox-cycling product of the AKR1C1 reaction, also induced AKR1C1 expression. Thus, BPQ formation by AKR1C1 results in both a chemical (redox-cycling) and a genetic (AKR1C1 induction) amplification of ROS in PAH-exposed cells. Because ROS have been implicated in both tumor initiation and tumor promotion, the amplification of ROS by this pathway may play a significant role in PAH carcinogenesis.

Antithrombotic effect of crotalin, a platelet membrane glycoprotein Ib antagonist from venom of Crotalus atrox

A potent platelet glycoprotein Ib (GPIb) antagonist, crotalin, with a molecular weight of 30 kD was purified from the snake venom of Crotalus atrox. Crotalin specifically and dose dependently inhibited aggregation of human washed platelets induced by ristocetin with IC50 of 2.4 microg/mL (83 nmol/L). It was also active in inhibiting ristocetin-induced platelet aggregation of platelet-rich plasma (IC50, 6.3 microg/mL). 125I-crotalin bound to human platelets in a saturable and dose-dependent manner with a kd value of 3.2 +/- 0.1 x 10(-7) mol/L, and its binding site was estimated to be 58,632 +/- 3, 152 per platelet. Its binding was specifically inhibited by a monoclonal antibody, AP1 raised against platelet GPIb. Crotalin significantly prolonged the latent period in triggering platelet aggregation caused by low concentration of thrombin (0.03 U/mL), and inhibited thromboxane B2 formation of platelets stimulated either by ristocetin plus von Willebrand factor (vWF), or by thrombin (0.03 U/mL). When crotalin was intravenously (IV) administered to mice at 100 to 300 microg/kg, a dose-dependent prolongation on tail bleeding time was observed. The duration of crotalin in prolonging tail bleeding time lasted for 4 hours as crotalin was given at 300 microg/kg. In addition, its in vivo antithrombotic activity was evidenced by prolonging the latent period in inducing platelet-rich thrombus formation by irradiating the mesenteric venules of the fluorescein sodium-treated mice. When administered IV at 100 to 300 microg/kg, crotalin dose dependently prolonged the time lapse in inducing platelet-rich thrombus formation. In conclusion, crotalin specifically inhibited vWF-induced platelet agglutination in the presence of ristocetin because crotalin selectively bound to platelet surface receptor-glycoprotein Ib, resulting in the blockade of the interaction of vWF with platelet membrane GPIb. In addition, crotalin is a potent antithrombotic agent because it pronouncedly blocked platelet plug formation in vivo.

Dexamethasone regulation of the rat 3alpha-hydroxysteroid/dihydrodiol dehydrogenase gene

Rat liver 3alpha-hydroxysteroid/dihydrodiol dehydrogenase (3alpha-HSD/DD), a member of the aldo-keto reductase superfamily, inactivates circulating steroid hormones and may contribute to the carcinogenicity of polycyclic aromatic hydrocarbons (PAHs) by oxidizing trans-dihydrodiols to reactive o-quinones with the concomitant generation of reactive oxygen species. The 3alpha-HSD/DD gene has been cloned, and its 5'-flanking region contains a negative response element (NRE; -797 to -498 bp) that may repress constitutive expression by binding to Oct transcription factors. Upstream from the NRE are three distal imperfect glucocorticoid response elements (GRE1, GRE2, and GRE3); in addition, a proximal imperfect GRE (GRE4) is adjacent to an Oct binding site in the NRE. When rat hepatocytes were cultured on Matrigel and exposed to dexamethasone (Dex), steady state levels of 3alpha-HSD/DD mRNA were increased 4-fold in a dose-dependent manner, yielding an EC50 value of 10 nM. Time to maximal response was 24 hr, and the effect was blocked with the anti-glucocorticoid RU486. Measurement of the half-life of 3alpha-HSD/DD mRNA, with and without Dex treatment, indicated that the increase in steady state mRNA levels was not due to increased mRNA stability. By contrast, nuclear run-off experiments using nuclei obtained from Dex-stimulated hepatocytes indicated that Dex increased transcription of the rat 3alpha-HSD/DD gene. Tandem repeats of the imperfect GRE1, GRE2, GRE3, and GRE4 were inserted into thymidine kinase-chloramphenicol acetyl-transferase vectors and cotransfected with the human glucocorticoid receptor into human hepatoma cells. On treatment with Dex, maximal trans-activation of the chloramphenicol acetyl-transferase reporter gene activity was mediated via the proximal GRE (GRE4). These data imply that GRE4 is a functional cis-element and that binding of the occupied glucocorticoid receptor to this element increases 3alpha-HSD/DD gene transcription. A model is proposed for the positive and negative regulation of the rat 3alpha-HSD/DD gene by the glucocorticoid receptor and Oct transcription factors, respectively.

Expression and characterization of recombinant type 2 3 alpha-hydroxysteroid dehydrogenase (HSD) from human prostate: demonstration of bifunctional 3 alpha/17 beta-HSD activity and cellular distribution

In androgen target tissues, 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) may regulate occupancy of the androgen receptor (AR) by catalyzing the interconversion of 5alpha-dihydrotestosterone (5alpha-DHT) (a potent androgen) and 3alpha-androstanediol (a weak androgen). In this study, a 3alpha-HSD cDNA (1170 bp) was isolated from a human prostate cDNA library. The human prostatic 3alpha-HSD cDNA encodes a 323-amino acid protein with 69.9%, 84.1%, 99.4%, and 87.9% sequence identity to rat liver 3alpha-HSD and human type 1, type 2, and type 3 3alpha-HSDs, respectively, and is a member of the aldo-keto reductase superfamily. The close homology with human type 2 3alpha-HSD suggests that it is either identical to this enzyme or a structural allele. Surprisingly, when the recombinant protein was expressed and purified from Escherichia coli, the enzyme did not oxidize androsterone when measured spectrophotometrically, an activity previously assigned to recombinant type 2 3alpha-HSD using this assay. Complete kinetic characterization of the purified protein using spectrophotometric, fluorometric, and radiometric assays showed that the catalytic efficiency favored 3alpha-androstanediol oxidation over 5alpha-DHT reduction. Using [14C]-5alpha-DHT as substrate, TLC analysis confirmed that the reaction product was [14C]-3alpha-androstanediol. However, in the reverse reaction, [3H]-3alpha-androstanediol was oxidized first to [3H]-androsterone and then to [3H]-androstanedione, revealing that the expressed protein possessed both 3alpha- and 17beta-HSD activities. The 17beta-HSD activity accounted for the higher catalytic efficiency observed with 3alpha-androstanediol. These findings indicate that, in the prostate, type 2 3alpha-HSD does not interconvert 5alpha-DHT and 3alpha-androstanediol but inactivates 5alpha-DHT through its 3-ketosteroid reductase activity. Levels of 3alpha-HSD mRNA were measured in primary cultures of human prostatic cells and were higher in epithelial cells than stromal cells. In addition, elevated levels of 3alpha-HSD mRNA were observed in epithelial cells derived from benign prostatic hyperplasia and prostate carcinoma tissues. Expression of 3alpha-HSD was not prostate specific, since high levels of mRNA were also found in liver, small intestine, colon, lung, and kidney. This study is the first complete characterization of recombinant type 2 3alpha-HSD demonstrating dual activity and cellular distribution in the human prostate.

Mammalian 3 alpha-hydroxysteroid dehydrogenases

Mammalian 3 alpha-hydroxysteroid dehydrogenases (3 alpha-HSDs) regulate steroid hormone levels. For example, hepatic 3 alpha-HSDs inactivate circulating androgens, progestins, and glucocorticoids. In target tissues they regulate access of steroid hormones to steroid hormone receptors. For example, in the prostate 3 alpha-HSD acts as a molecular switch and controls the amount of 5 alpha-dihydrotestosterone that can bind to the androgen receptor, while in the brain 3 alpha-HSD can regulate the amount of tetrahydrosteroids that can alter GABAa receptor function. Molecular cloning indicates that these mammalian 3 alpha-HSDs belong to the aldo-keto reductase superfamily and that they are highly homologous proteins. Using the three-dimensional structure of rat liver 3 alpha-HSD as a template for site-directed mutagenesis, details regarding structure function relationships, including catalysis and cofactor and steroid hormone recognition have been elucidated. These details may be relevant to all mammalian 3 alpha-HSDs.

Cloning, sequencing, and functional analysis of the 5'-flanking region of the rat 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase gene

Rat liver 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase (3 alpha-HSD/DD) is a member of the aldo-keto reductase gene superfamily. It displays high constitutive expression and inactivates circulating steroid hormones and suppresses the formation of polycyclic aromatic hydrocarbon anti- and syn-diol-epoxides (ultimate carcinogens). To elucidate mechanisms responsible for constitutive expression of the 3 alpha-HSD/DD gene a rat genomic library obtained from adult Sprague-Dawley female liver (HaeIII partial digest) was screened, using a probe corresponding to the 5'-end of the cDNA (-15 to +250), and a 15.8-kb genomic clone was isolated. Sequencing revealed that 6.3 kb contained exon 1 (+16 to +138 bp) plus additional introns and exons. The transcription start site (+1) was located by primer extension analysis, and the initiation codon, ATG, was located at +55 bp. The remaining 9.5 kb represented the 5'-flanking region of the rat 3 alpha-HSD/DD gene. A 1.6-kb fragment of this region was sequenced. A TATTTAA sequence (TATA box) was found at 33 bp upstream from the major transcription start site. cis-acting elements responsible for the constitutive expression of the rat 3 alpha-HSD/DD gene were located on the 5'-flanking region by transient transfection of reporter-gene (chloramphenicol acetyl transferase, CAT) constructs into human hepatoma cells (HepG2). CAT assays identified the basal promoter between (-199 and +55 bp), the presence of a proximal enhancer (-498 to -199 bp) which stimulated CAT activity 6-fold, the existence of a powerful silencer (-755 to -498 bp), and a strong distal enhancer (-4.0 to -2.0 kb) which increased CAT activity by 20-40-fold. A computer search of available consensus sequences for trans-acting factors revealed that a cluster of Oct-sites were uniquely located in the silencer region. Using the negative response element (-797 to -498 bp) as a probe and nuclear extracts from HepG2 cells, three bands were identified by gel mobility shift assay, indicating the presence of protein binding sites in this proposed negative response element. All three bands were supershifted with anti-Oct-1 mAb, suggesting that Oct-1 may be the repressor. The 5'-flanking region also contained an AP-1 site, an estrogen response element, and a glucocorticoid response element, which together may comprise a steroid response unit.(ABSTRACT TRUNCATED AT 400 WORDS)

A reverse mutagenicity assay for alkylating agents based on a point mutation in the beta-lactamase gene at the active site serine codon

The serine at the active site of beta-lactamase is responsible for the ester link to the acyl group of beta-lactam during hydrolysis of the substrate to its acid derivatives. A construct was made from a plasmid in which the active-site serine of beta-lactamase was substituted by glycine by site-directed mutation. This mutation results in the loss of beta-lactamase activity. This plasmid was used to transform Salmonella typhimurium TA1535. When the new strain JK947 was treated with a mutagen such as N-methyl-N'-nitro-nitrosoguanidine (MNNG), the bacteria could be recovered as they became ampicillin resistant. The sequence of the active-site serine codon in these revertants was mutated from GGC to AGC. Based upon these findings, we developed a model reverse mutagenicity assay. In this procedure, we treated JK947 with a test chemical, such as N-methyl-nitrosourea (MNU), dimethyl sulphate (DMS) or methylmethane sulphonate (MMS), for 30 min, and then scored the revertants on agar plates containing 50 micrograms/ml ampicillin after incubation at 37 degrees C for 16 h. MNU and MNNG were more potent than DMS and MMS in this assay. Treatment with MNU and MNNG resulted in larger colony numbers in our test than in the Ames test. However, our test was less sensitive to DMS and MMS than the Ames test.

Tight binding inhibitors of 85-kDa phospholipase A2 but not 14-kDa phospholipase A2 inhibit release of free arachidonate in thrombin-stimulated human platelets

An analogue of arachidonic acid in which the COOH group is replaced by a trifluoromethyl ketone group (COCF3) has recently been shown to be a tight binding inhibitor of the 85-kDa cytosolic phospholipase A2 that is found in platelets and other cells (Street, I. P., Lin, H.-K., Laliberté, F., Ghomashchi, F. G., Wang, Z., Perrier, H., Tremblay, N. M., Huang, Z., Weech, P. K., and Gelb, M. H. (1993) Biochemistry 32, 5935-5940). This trifluoromethyl ketone inhibits most of the arachidonate release from the phospholipid pool in thrombin-stimulated human platelets at concentrations of 0-40 microM with 4 x 10(8) platelets/ml. A structure-function analysis of related compounds reveals a good correlation between the inhibition of the purified phospholipase A2 and the blockage of arachidonate release in platelets. A number of recently described potent inhibitors of the 14-kDa phospholipase A2 that is secreted from activated platelets have no effect on the level of free arachidonate production. Furthermore, the addition of a large amount of recombinant 14-kDa phospholipase A2 to platelets does not produce free arachidonate, and it does not alter the amount of arachidonate released following platelet activation with thrombin. These studies provide strong pharmacological evidence for the role of the cytosolic phospholipase A2 in producing most, if not all, of the liberated arachidonate in thrombin-stimulated human platelets, and they show that tight binding membrane-residing inhibitors of the cytosolic phospholipase A2 can block the eicosanoid cascade in living cells.

Tumor suppressor p53 is a regulator of bcl-2 and bax gene expression in vitro and in vivo

The p53 tumor suppressor gene product can induce apoptotic cell death through an unknown mechanism. Here we demonstrate that a temperature-sensitive p53 induces temperature-dependent decreases in the expression of the apoptosis-suppressing gene bcl-2 in the murine leukemia cell M1, while simultaneously stimulating increases in the expression of bax, a gene which encodes a dominant-inhibitor of the Bcl-2 protein. Mice deficient in p53 exhibit increases in Bcl-2 and decreases in Bax protein levels in several tissues as determined by immunohistochemical and immunoblot methods. The findings suggest a potential mechanism by which p53 regulates apoptosis, as well as responses to radiation and chemotherapeutic drugs in cancer.

Immediate early up-regulation of bax expression by p53 but not TGF beta 1: a paradigm for distinct apoptotic pathways

Recently, both Bcl-2, which promotes cell survival, and Bax, which promotes cell death, have been implicated as major players in the control of apoptotic pathways, and it has been suggested that the ratio of Bcl-2 and Bax protein controls the relative susceptibility of cells to death stimuli. We have used M1 myeloid leukemia cells and genetically engineered M1 variants as a model system to study apoptosis induced by two distinct apoptotic stimuli. This includes apoptosis induced by activation of wild type p53 function of a temperature sensitive p53 transgene expressed in M1 cells, which do not express endogenous p53, and apoptosis induced by TGF beta 1. It is shown that the kinetics of apoptosis induced by p53 is more rapid than apoptosis induced by TGF beta 1. It is also shown that ectopic expression of Bcl-2, at levels which blocked TGF beta 1-induced apoptosis of M1 cells, delayed, but did not block, p53-induced apoptosis. Both p53 and TGF beta 1 down-regulated endogenous Bcl-2 expression, but only p53 up-regulated Bax expression, where bax has been identified as a p53 immediate early response gene. Thus, the p53-mediated up-regulation of Bax may provide at least a partial explanation for the more rapid rate of apoptosis induced by p53 compared to by TGF beta 1, as well as for the ineffectiveness of ectopoic Bcl-2 to abrogate p53-mediated apoptosis. These findings provide first insights to the molecular mechanisms which mediate p53-induced apoptosis, identifying bax and bcl-2 as p53 regulated genes, and serve as a paradigm of how the intracellular balance of Bcl-2 to Bax is differentially altered by distinct death stimuli.

The novel primary response gene MyD118 and the proto-oncogenes myb, myc, and bcl-2 modulate transforming growth factor beta 1-induced apoptosis of myeloid leukemia cells

Cell numbers are regulated by a balance among proliferation, growth arrest, and programmed cell death. A profound example of cell homeostasis, controlled throughout life, is the complex process of blood cell development, yet little is understood about the intracellular mechanisms that regulate blood cell growth arrest and programmed cell death. In this work, using transforming growth factor beta 1 (TGF beta 1)-treated M1 myeloid leukemia cells and genetically engineered M1 cell variants, the regulation of growth arrest and apoptosis was dissected. Blocking of early expression of MyD118, a novel differentiation primary response gene also shown to be a primary response gene induced by TGF beta 1, delayed TGF beta 1-induced apoptosis, demonstrating that MyD118 is a positive modulator of TGF beta 1-mediated cell death. Elevated expression of bcl-2 blocked the TGF beta 1-induced apoptotic pathway but not growth arrest induced by TGF beta 1. Deregulated expression of either c-myc or c-myb inhibited growth arrest and accelerated apoptosis, demonstrating for the first time that c-myb plays a role in regulating apoptosis. In all cases, the apoptotic response was correlated with the level of MyD118 expression. Taken together, these findings demonstrate that the primary response gene MyD118 and the c-myc, c-myb, and bcl-2 proto-oncogenes interact to modulate growth arrest and apoptosis of myeloid cells.

Slow- and tight-binding inhibitors of the 85-kDa human phospholipase A2

A trifluoromethyl ketone analogue of arachidonic acid in which the COOH group is replaced with COCF3 (AACOCF3) was prepared and found to be a tight- and slow-binding inhibitor of the 85-kDa cytosolic human phospholipase A2 (cPLA2). Enzyme inhibition was observed when AACOCF3 was tested in assays using either phospholipid vesicles or phospholipid/Triton X-100 mixed micelles. The fact that the inhibition developed over several minutes in both assays establishes that AACOCF3 inhibits by direct binding to the enzyme rather than by decreasing the fraction of enzyme bound to the substrate interface. From the measured values of the inhibitor association and dissociation rate constants, an upper limit of the equilibrium dissociation constant for the Ca(2+).AACOCF3.PLA2 complex of 5 x 10(-5) mole fraction was obtained. Thus, detectable inhibition of cPLA2 by AACOCF3 occurs when this compound is present in the assay at a level of one inhibitor per several thousand substrates. Arachidonic acid analogues in which the COOH group is replaced by COCH3, CH(OH)CF3, CHO, or CONH2 did not detectably inhibit the cPLA2. The arachidonyl ketones AACOCF2CF3 and AACOCF2Cl were found by 19F NMR to be less hydrated than AACOCF3 in phospholipid/Triton X-100 mixed micelles, and compared to AACOCF3 these compounds are also weaker inhibitors of cPLA2. In keeping with the fact that cPLA2 displays substrate specificity for arachidonyl-containing phospholipids, the arachidic acid analogue C19H39COCF3 is a considerably less potent inhibitor compared to AACOCF3.(ABSTRACT TRUNCATED AT 250 WORDS)

Human nonpancreatic secreted phospholipase A2: interfacial parameters, substrate specificities, and competitive inhibitors

The rate and equilibrium parameters for the interfacial catalysis by recombinant human nonpancreatic secreted phospholipase A2 were determined. Results show that the enzyme binds to anionic interfaces with considerably higher affinity than to zwitterionic interfaces. The extent of hydrolysis per enzyme on anionic vesicles in the processive scooting mode shows that the enzyme is fully catalytically active as a monomer. Among several secreted phospholipases A2 tested, the human nonpancreatic secreted enzyme is unique in its ability to undergo slow intervesicle exchange either by dissociation from the interface followed by binding to a different vesicle or by promoting the fusion of vesicles. The equilibrium dissociation constants for calcium, substrate analogs, reaction products, and several competitive inhibitors bound to the enzyme at the interface were determined by monitoring the ligand-conferred protection of the active site histidine residue from alkylation by phenacyl bromide. The interfacial Michaelis-Menten parameters were determined from the analysis of the entire reaction progress curve and also by monitoring the effect of competitive inhibitors on the initial rate of hydrolysis in the scooting mode. The interfacial Michaelis constant (KM*) for the substrate 1,2-dimyristoylglycero-sn-3-phosphomethanol was determined to be considerably above the maximal attainable mole fraction of unity for the substrate in the bilayer. Substrate specificity studies show that the enzyme does not significantly discriminate between phospholipids that differ in the type of polar head group or in the degree of unsaturation of the fatty acyl chains. Competitive inhibitors are described that display a high degree of selectivity for binding to the nonpancreatic versus pancreatic phospholipase A2. The kinetic properties of the human nonpancreatic secreted phospholipase A2 suggest that the enzyme has evolved to hydrolyze substrates at anionic interfaces and at high calcium concentrations.

Macrophage antimicrobial functions in a chicken MHC chromosome dosage model

Macrophages respond to certain inflammatory signals with a marked increase in respiratory burst and the production of reactive oxygen intermediates; these metabolites play an essential role in the destruction of invading microorganisms. In this study, macrophage antibacterial inflammatory responses were compared among chickens having two (disomic), three (trisomic), or four (tetrasomic) copies of the major histocompatibility complex (MHC)-encoding microchromosome (B15 haplotype). Phorbol myristate acetate (PMA)-stimulated superoxide anion (O2-) production by cross-linked dextran (Sephadex)-elicited peritoneal macrophages was measured at early (4 h), intermediate (24 h), and late (42 h) stages of the inflammatory response using ferrocytochrome c reduction. Significantly elevated O2- production was observed for trisomic versus disomic macrophages during both early and intermediate stages of the inflammatory response. Late in the response, tetrasomic macrophages produced a significantly higher level of O2- than disomic cells. When PMA was used to trigger hydrogen peroxide (H2O2) production, no significant genotype difference was found for any stage of the inflammatory response. Phagocytosis of heat-killed Salmonella enteritidis by macrophages differed among the three genotypes: trisomic macrophages were superior to disomic cells during early inflammation, no genotypic difference was observed at the intermediate stage, and disomic cells had greater phagocytic capacity than aneuploid macrophages late in the response. Likewise, when S. enteritidis was cultured with macrophages to induce oxygen intermediate secretion, H2O2 production followed a kinetic pattern among the genotypes similar to that observed for bacterial phagocytosis. Endogenous superoxide dismutase (SOD), catalase, and glutathione peroxidase (GP) activities were determined for the macrophages during intermediate and late inflammatory stages. Tetrasomic macrophages had reduced SOD activity at the late stage, no significant difference was observed in catalase activity among genotypes at either time point, and trisomic macrophages had enhanced GP activity compared to disomic cells at both time points. These results indicate that differences in MHC gene dosage are associated with differences in chicken macrophage activation for the acquisition of selected antibacterial functions.

Physicochemical characterization of beta-crystallins from bovine lenses: hydrodynamic and aggregation properties

A detailed investigation of the hydrodynamic and aggregation behaviors has been made on the beta-crystallins of bovine lens. Results from this study indicated that beta H (high-molecular-weight beta-crystallin) and beta L (low-molecular-weight beta-crystallin) exhibited considerable heterogeneity in their native structures and subunit polypeptides. Low-speed sedimentation equilibrium showed a heterogeneous paucidisperse system in each beta-crystallin fraction. Viscosity and circular dichroism studies pointed to a compact and globular shape and the presence of beta-sheet and beta-turns in these crystallins. Dissociation of beta H by urea and guanidinium HCl followed by reassociation during gel-filtration chromatography produced an elution pattern with two fractions corresponding to beta L crystallin and high-molecular-weight aggregates without the formation of native beta H. By contrast, under similar treatment, about 60% beta L reassociated into the correct native structure and the rest into high-molecular-weight fractions. Amino acid analyses of beta H and beta L and their corresponding subunit polypeptides demonstrated the close similarity of these crystallins. Trace element analyses indicated that both Ca and Mg are present in beta H and beta L crystallins and may be involved in maintaining the native quarternary structures of these proteins.

Heritabilities of and genetic correlations among six health problems in Holstein cows

Information from 7712 lactations of Holstein dairy cows was collected from 33 commercial herds around Ithaca, NY in the 3 yr from 1981 to 1983. The data were divided into subsets corresponding to lactation 1, lactation 2, and lactation 3 or greater. To estimate heritabilities of dystocia, retained placenta, metritis, ovarian cysts, milk fever, and mastitis, a mixed linear model (herd-year fixed and sire random effects) with 0 or 1 as the observed response was used. Variance components were estimated using Henderson's Method 3. The results show moderate heritabilities (.15 to .40) for dystocia, metritis, milk fever, and mastitis and low heritability (less than .12) for retained placenta and cystic ovaries. Genetic correlations between dystocia, retained placenta, metritis, and mastitis were moderate in size and positive, whereas cystic ovaries were correlated negatively with dystocia and retained placenta. A general reproductive health trait (dystocia, retained placenta, metritis, cystic ovaries, and milk fever combined in one trait) also was analyzed. The estimated heritability of this trait was .21, .11, and .00 for first calf heifers, second lactation cows, and older cows, respectively.

A re-evaluation of the molecular size of duck epsilon-crystallin and its comparison with avian lactate dehydrogenases

A biochemical comparison of epsilon-crystallin isolated from the duck lens and lactate dehydrogenases of chicken heart has been made in order to establish the structural and functional identities of these two proteins. The native molecular weight of epsilon-crystallin was re-examined by combining sedimentation and gel-filtration data. It was found that epsilon-crystallin is 150 kDa in contrast to the 120 kDa reported previously for this crystallin. Subunit cross-linking experiments corroborated that lactate dehydrogenase and epsilon-crystallin both exist as tetramers of four identical subunits in their native quaternary structures. Amino acid compositions plus N-terminal analyses revealed no differences between the two proteins. Duck epsilon-crystallin exhibited high enzymatic activity of lactate dehydrogenases even after a long period of storage, and showed characteristic thermostability at 50 degrees C for several hours. Comparison of the enzyme activity of duck lens homogenate with those of heart, liver and muscle tissues revealed that duck lens is a much richer source than other tissues for the isolation and characterization of this important enzyme which appears also as a structural protein in the lens.

Biochemical characterization of lens crystallins from three mammalian species

Lens crystallins were isolated from the homogenates of mammalian eye lenses derived from three different species by gel permeation chromatography and characterized by SDS-gel electrophoresis, isoelectric focusing, amino acid analysis and N-terminal sequence analysis. Five fractions corresponding to HM alpha-, alpha-, beta H-, beta L- and gamma-crystallins were obtained for the crystallins from these phylogenetically distant species. The native molecular masses for these purified fractions and their polypeptide compositions were determined by gel filtration and SDS-gel electrophoresis respectively, revealing the typical subunit compositions for each classified crystallin. The gel pattern of gamma-crystallins from the marmot lens appeared to be more complex than those of gibbon and deer lenses. Comparison of the amino acid contents of each orthologous class of mammalian crystallins with those of evolutionarily distant species still exhibited similarity in their amino acid compositions. The charge heterogeneity of each crystallin fraction can be detected by isoelectric focusing under denaturing conditions. N-terminal sequence analysis of the crystallin fractions revealed that all fractions except that of gamma-crystallin are N-terminally blocked. Extensive sequence similarity between mammalian gamma-crystallin polypeptides were found, which suggested the close relatedness of gamma-crystallins amongst different species of mammals and also established the heterogeneous nature of this multigene family.

Characterization of phospholipase A inhibition of stereospecific opiate binding and its reversal by bovine serum albumin

Opiate receptor binding is inhibited by phospholipase A from some sources, whereas the enzyme from other sources is inactive even at much higher concentrations. Evidence is presented that an active enzymatic site is required for inhibition and that the degree of inhibition seems to correlate with the extent of phospholipolysis. The inhibition is reversed almost completely by treatment with 0.5 to 1% bovine serum albumin, even up to 90% inhibition by phospholipase. As more enzyme is added or incubation time is increased, the extent of reversal diminishes. Based on our evidence, the most likely explanation of these results is that the inhibition of opiate binding activity by phospholipase A is due to the toxicity of the products of phospholipolysis and that bovine serum albumin reverses the inhibition by removing these products from the membranes, thereby restoring the active conformation of the receptors.

Differential effects of cholesterol and lanosterol on artificial membranes

The effects of cholesterol, 4,4-dimethylcholesterol, and lanosterol (4,4',14alpha-trimethyl-delta8,24-cholestadiene-3beta-ol) on some properties of lecithin vesicles have been compared. Unlike cholesterol, lanosterol retards the exit of trapped glucose from phospholipid vesicles only slightly. The 13C nuclear magnetic resonance spectrum of cholesterol/lecithin vesicles shows no resonances attributable to the sterol. By contrast, several resonances attributable to quaternary carbon atoms or methyl groups are seen in the 13C nuclear magnetic resonance spectrum of lanosterol/lecithin vesicles, indicating that lanosterol is much less immobilized than cholesterol. Because the membrane behavior of 4,4-dimethylcholesterol is closely similar to that of cholesterol, it is concluded that the axial 14-alpha-methyl group is responsible for the lessened membrane immobilization of lanosterol. The results emphasize the importance of a planar sterol alpha-face for interaction with phospholipid acyl chains.