AMPK inhibition sensitizes acute leukemia cells to BH3 mimetic-induced cell death

BH3 mimetics, including the BCL2/BCLXL/BCLw inhibitor navitoclax and MCL1 inhibitors S64315 and tapotoclax, have undergone clinical testing for a variety of neoplasms. Because of toxicities, including thrombocytopenia after BCLXL inhibition as well as hematopoietic, hepatic and possible cardiac toxicities after MCL1 inhibition, there is substantial interest in finding agents that can safely sensitize neoplastic cells to these BH3 mimetics. Building on the observation that BH3 mimetic monotherapy induces AMP kinase (AMPK) activation in multiple acute leukemia cell lines, we report that the AMPK inhibitors (AMPKis) dorsomorphin and BAY-3827 sensitize these cells to navitoclax or MCL1 inhibitors. Cell fractionation and phosphoproteomic analyses suggest that sensitization by dorsomorphin involves dephosphorylation of the proapoptotic BCL2 family member BAD at Ser75 and Ser99, leading BAD to translocate to mitochondria and inhibit BCLXL. Consistent with these results, BAD knockout or mutation to BAD S75E/S99E abolishes the sensitizing effects of dorsomorphin. Conversely, dorsomorphin synergizes with navitoclax or the MCL1 inhibitor S63845 to induce cell death in primary acute leukemia samples ex vivo and increases the antitumor effects of navitoclax or S63845 in several xenograft models in vivo with little or no increase in toxicity in normal tissues. These results suggest that AMPK inhibition can sensitize acute leukemia to multiple BH3 mimetics, potentially allowing administration of lower doses while inducing similar antineoplastic effects.

A BAK subdomain that binds mitochondrial lipids selectively and releases cytochrome C

How BAK and BAX induce mitochondrial outer membrane (MOM) permeabilization (MOMP) during apoptosis is incompletely understood. Here we have used molecular dynamics simulations, surface plasmon resonance, and assays for membrane permeabilization in vitro and in vivo to assess the structure and function of selected BAK subdomains and their derivatives. Results of these studies demonstrate that BAK helical regions α5 and α6 bind the MOM lipid cardiolipin. While individual peptides corresponding to these helical regions lack the full biological activity of BAK, tandem peptides corresponding to α4-α5, α5-α6, or α6-α7/8 can localize exogenous proteins to mitochondria, permeabilize liposomes composed of MOM lipids, and cause MOMP in the absence of the remainder of the BAK protein. Importantly, the ability of these tandem helices to induce MOMP under cell-free conditions is diminished by mutations that disrupt the U-shaped helix-turn-helix structure of the tandem peptides or decrease their lipid binding. Likewise, BAK-induced apoptosis in intact cells is diminished by CLS1 gene interruption, which decreases mitochondrial cardiolipin content, or by BAK mutations that disrupt the U-shaped tandem peptide structure or diminish lipid binding. Collectively, these results suggest that BAK structural rearrangements during apoptosis might mobilize helices involved in specific protein-lipid interactions that are critical for MOMP.

Fatty acid synthase (FASN) regulates the mitochondrial priming of cancer cells

Inhibitors of the lipogenic enzyme fatty acid synthase (FASN) have attracted much attention in the last decade as potential targeted cancer therapies. However, little is known about the molecular determinants of cancer cell sensitivity to FASN inhibitors (FASNis), which is a major roadblock to their therapeutic application. Here, we find that pharmacological starvation of endogenously produced FAs is a previously unrecognized metabolic stress that heightens mitochondrial apoptotic priming and favors cell death induction by BH3 mimetic inhibitors. Evaluation of the death decision circuits controlled by the BCL-2 family of proteins revealed that FASN inhibition is accompanied by the upregulation of the pro-death BH3-only proteins BIM, PUMA, and NOXA. Cell death triggered by FASN inhibition, which causally involves a palmitate/NADPH-related redox imbalance, is markedly diminished by concurrent loss of BIM or PUMA, suggesting that FASN activity controls cancer cell survival by fine-tuning the BH3 only proteins-dependent mitochondrial threshold for apoptosis. FASN inhibition results in a heightened mitochondrial apoptosis priming, shifting cells toward a primed-for-death state "addicted" to the anti-apoptotic protein BCL-2. Accordingly, co-administration of a FASNi synergistically augments the apoptosis-inducing activity of the dual BCL-X_L/BCL-2 inhibitor ABT-263 (navitoclax) and the BCL-2 specific BH3-mimetic ABT-199 (venetoclax). FASN inhibition, however, fails to sensitize breast cancer cells to MCL-1- and BCL-X_L-selective inhibitors such as S63845 and A1331852. A human breast cancer xenograft model evidenced that oral administration of the only clinically available FASNi drastically sensitizes FASN-addicted breast tumors to ineffective single-agents navitoclax and venetoclax in vivo. In summary, a novel FASN-driven facet of the mitochondrial priming mechanistically links the redox-buffering mechanism of FASN activity to the intrinsic apoptotic threshold in breast cancer cells. Combining next-generation FASNis with BCL-2-specific BH3 mimetics that directly activate the apoptotic machinery might generate more potent and longer-lasting antitumor responses in a clinical setting.

Characterization of a RAD51C-silenced high-grade serous ovarian cancer model during development of PARP inhibitor resistance

Acquired PARP inhibitor (PARPi) resistance in BRCA1- or BRCA2-mutant ovarian cancer often results from secondary mutations that restore expression of functional protein. RAD51C is a less commonly studied ovarian cancer susceptibility gene whose promoter is sometimes methylated, leading to homologous recombination (HR) deficiency and PARPi sensitivity. For this study, the PARPi-sensitive patient-derived ovarian cancer xenograft PH039, which lacks HR gene mutations but harbors RAD51C promoter methylation, was selected for PARPi resistance by cyclical niraparib treatment in vivo. PH039 acquired PARPi resistance by the third treatment cycle and grew through subsequent treatment with either niraparib or rucaparib. Transcriptional profiling throughout the course of resistance development showed widespread pathway level changes along with a marked increase in RAD51C mRNA, which reflected loss of RAD51C promoter methylation. Analysis of ovarian cancer samples from the ARIEL2 Part 1 clinical trial of rucaparib monotherapy likewise indicated an association between loss of RAD51C methylation prior to on-study biopsy and limited response. Interestingly, the PARPi resistant PH039 model remained platinum sensitive. Collectively, these results not only indicate that PARPi treatment pressure can reverse RAD51C methylation and restore RAD51C expression, but also provide a model for studying the clinical observation that PARPi and platinum sensitivity are sometimes dissociated.

CDK2-Mediated Upregulation of TNFα as a Mechanism of Selective Cytotoxicity in Acute Leukemia

Although inhibitors of the kinases CHK1, ATR, and WEE1 are undergoing clinical testing, it remains unclear how these three classes of agents kill susceptible cells and whether they utilize the same cytotoxic mechanism. Here we observed that CHK1 inhibition induces apoptosis in a subset of acute leukemia cell lines in vitro, including TP53-null acute myeloid leukemia (AML) and BCR/ABL-positive acute lymphoid leukemia (ALL), and inhibits leukemic colony formation in clinical AML samples ex vivo. In further studies, downregulation or inhibition of CHK1 triggered signaling in sensitive human acute leukemia cell lines that involved CDK2 activation followed by AP1-dependent TNF transactivation, TNFα production, and engagement of a TNFR1- and BID-dependent apoptotic pathway. AML lines that were intrinsically resistant to CHK1 inhibition exhibited high CHK1 expression and were sensitized by CHK1 downregulation. Signaling through this same CDK2-AP1-TNF cytotoxic pathway was also initiated by ATR or WEE1 inhibitors in vitro and during CHK1 inhibitor treatment of AML xenografts in vivo. Collectively, these observations not only identify new contributors to the antileukemic cell action of CHK1, ATR, and WEE1 inhibitors, but also delineate a previously undescribed pathway leading from aberrant CDK2 activation to death ligand-induced killing that can potentially be exploited for acute leukemia treatment. SIGNIFICANCE: This study demonstrates that replication checkpoint inhibitors can kill AML cells through a pathway involving AP1-mediated TNF gene activation and subsequent TP53-independent, TNFα-induced apoptosis, which can potentially be exploited clinically.

[Biography of Moody Meng]

Moody Meng(1897-1983) was a pioneer of pharmacy in China. He was the main editor of the first Chinese Pharmacopoeia, the first president of the National College of Pharmacy (now China Pharmaceutical University), the first director of Chongqing Union Pharmaceutical Factory during the Anti-Japanese War and the first director of the China National Institute for the Control of Pharmaceutical and Biological Products. He made important contributions in many fields of pharmacy in China.

53BP1 as a potential predictor of response in PARP inhibitor-treated homologous recombination-deficient ovarian cancer

OBJECTIVE

Poly(ADP-ribose) polymerase (PARP) inhibitors have shown substantial activity in homologous recombination- (HR-) deficient ovarian cancer and are undergoing testing in other HR-deficient tumors. For reasons that are incompletely understood, not all patients with HR-deficient cancers respond to these agents. Preclinical studies have demonstrated that changes in alternative DNA repair pathways affect PARP inhibitor (PARPi) sensitivity in ovarian cancer models. This has not previously been assessed in the clinical setting.

METHODS

Clonogenic and plasmid-based HR repair assays were performed to compare BRCA1-mutant COV362 ovarian cancer cells with or without 53BP1 gene deletion. Archival biopsies from ovarian cancer patients in the phase I, open-label clinical trial of PARPi ABT-767 were stained for PARP1, RAD51, 53BP1 and multiple components of the nonhomologous end-joining (NHEJ) DNA repair pathway. Modified histochemistry- (H-) scores were determined for each repair protein in each sample. HRD score was determined from tumor DNA.

RESULTS

53BP1 deletion increased HR in BRCA1-mutant COV362 cells and decreased PARPi sensitivity in vitro. In 36 women with relapsed ovarian cancer, responses to the PARPi ABT-767 were observed exclusively in cancers with HR deficiency. In this subset, 7 of 18 patients (39%) had objective responses. The actual HRD score did not further correlate with change from baseline tumor volume (r = 0.050; p = 0.87). However, in the HR-deficient subset, decreased 53BP1 H-score was associated with decreased antitumor efficacy of ABT-767 (r = -0.69, p = 0.004).

CONCLUSION

Differences in complementary repair pathways, particularly 53BP1, correlate with PARPi response of HR-deficient ovarian cancers.

Measurement of BH3-only protein tolerance

The BCL2 family of proteins regulates cellular life and death decisions. Among BCL2 family members, BH3-only proteins have critical roles by neutralizing antiapoptotic family members, as well as directly activating BAX and BAK. Despite widespread occurrence of BH3-only protein upregulation in response to various stresses, this process is rarely quantified. Moreover, it is unclear whether all BH3-only proteins are equipotent at inducing cell death. Here we show that BH3-only proteins increase as much as 15- to 20-fold after various treatments and define a parameter, termed BH3-only tolerance, which measures how many copies of a particular BH3-only protein can be expressed before the majority of cells in a population undergo apoptosis. We not only assess the relative contributions of anti- and proapoptotic BCL2 family members to BH3-only tolerance, but also illustrate how the study of this parameter can be used to understand cellular sensitivity to anticancer drugs and new combinations. These observations provide a new quantitative framework for assessing apoptotic susceptibility under various conditions.

[Association of vitamin D receptor gene polymorphisms with idiopathic hypoparathyroidism phenotypes]

Objective: To explore the association of vitamin D receptor (VDR) gene polymorphisms with idiopathic hypoparathyroidism (IHP). Methods: Two hundred and three patients with IHP and 209 healthy age- and sex-matched subjects were recruited at Peking Union Medical College Hospital between December 1987 and December 2015 as case group and control group, respectively. The VDR gene polymorphisms including rs739837, rs3847987 and rs2228570 were analyzed by Sequenom Mass Array. The frequency of different genotypes and alleles was detected, then their association with pathogenesis of IHP was analyzed. The clinical characteristics, biochemical indicators were collected to explore the genotype-phenotype relationship. The role of reactions to vitamin D treatment were compared between patients with different genotypes. Results: There was no significant difference in the genotypes and allele frequency distribution of SNPs between the two groups (all P>0.05). However, in the initially-treated patients, the genotypes of rs739837 were related to serum calcium level (r=0.186, P=0.026). And patients with GG genotype of rs2228750 had higher level of urine calcium than GA and AA (277.7 mg vs 141.1 mg, P=0.024) after treating with oral vitamin D(3) and calcium. Conclusions: Functional SNPs of VDR gene including rs739837, rs3847987 and rs2228570 might be irrelevant to the pathogenesis of IHP. But the genotypes of rs739837 were related to serum calcium level, and rs2228570 may have an effect on the different responses to vitamin D and its analogues in IHP patients.

[Clinical characteristics of adult-onset primary hypoparathyroidism: a retrospective analysis of 200 cases]

Objective: To study the clinical characteristics of primary hypoparathyroidism in adults. Methods: The clinical data of 200 cases with adult-onset primary hypoparathyroidism in Peking Union Medical College Hospital during December 1987 to December 2015 were collected and analyzed retrospectively. Among them, 128 cases were followed up for a median period of 3 years. Results: The major manifestations at their first visits were tetany and numbness in the distal extremities(81.5%, 163/200 and 62.0%, 124/200). Thirty-two percent of the cases (62 cases) had history of seizures, and 60.9%(98/161) and 74.4%(96/129) of them were with intracerebral calcifications and cataracts, respectively.Most of subjects(155/200)had more than one year delay in diagnosis. Hypercalciuria occurred in 67.2%(86/128) of the cases during the follow-up. No significant differences in the clinical characteristics and biochemical markers between the hypercalciuria subjects and the non-hypercalciuria subjects. Renal nephrocalcinosis or stones were found in 6.5%(5/77) of the cases, and kidney function decreased in 6.6%(6/91) of the patients. Kidney function was negatively associated with age and duration of disease. Conclusions: The predominant manifestations of primary hypoparathyroidism in adults included tetany and numbness in the distal extremities and seizures. It is often misdiagnosed. Calcium supplement combined with vitamin D or its metabolites effectively relieve clinical symptoms and signs. The serum and urinary calcium levels should be monitored frequently to reduce renal complications.

Mitochondrial apoptosis and BH3 mimetics

The BCL2-selective BH3 mimetic venetoclax was recently approved for the treatment of relapsed, chromosome 17p-deleted chronic lymphocytic leukemia (CLL) and is undergoing extensive testing, alone and in combination, in lymphomas, acute leukemias, and solid tumors. Here we summarize recent advances in understanding of the biology of BCL2 family members that shed light on the action of BH3 mimetics, review preclinical and clinical studies leading to the regulatory approval of venetoclax, and discuss future investigation of this new class of antineoplastic agent.

[The expression of p27Kip1 and β-catenin in multiple endocrine neoplasia type 1-related parathyroid tumors]

Objective: To explore tissue expression of cyclin-dependent kinase inhibitor p27^Kip1 and β-catenin in multiple endocrine neoplasia type1 (MEN1)-related parathyroid tumors (MHPT). Methods: Immunohistochemistry was performed to analyze the expression of p27^Kip1 and β-catenin in parathyroid glands from 31 subjects with MHPT collected at Peking Union Medical College Hospital from 2002 to 2013. Five normal parathyroid glands were used as control. Results: In MHPT subjects, nuclear expression of p27^Kip1 was absent in 4 (12.9%), weak in 10 (32.3%) and moderated staining in 17 parathyroid specimens (54.8%), respectively. While, in normal subjects, the nuclear expression of p27^Kip1 was observed in all subjects and was stronger than that from MHPT subjects (P=0.001). As to the expression of β-catenin, normal parathyroid showed a distinct to moderate membrane staining, a moderate to weak cytoplasmic staining and negative nuclear staining. Similarly, MHPT exhibited a marked to moderate membrane (P=0.087), a moderated to weak cytoplasmic (P=0.357), and negative nuclear β-catenin staining. Conclusions: The expression of p27^Kip1 is reduced or absent in MHPT tissue, and no nuclear expression of β-catenin is observed in the tumors, which suggesting p27^Kip1, but not β-catenin nuclear accumulation, play a role in the development of the tumors.

[The clinical characteristics of 128 childhood- and adolescent-onset hypoparathyroidism in Peking Union Medical College Hospital: a retrospective analysis]

Objective: To study the clinical characteristics of childhood- and adolescent- onset hypoparathyroidism. Methods: The clinical data of 128 hypoparathyroidism patients with onset before the age of 18 years were collected and analyzed retrospectively. Results: The predominant features of the hypoparathyroidism were carpopedal spasm (89.3%, 108/121) and seizures (66.1%, 84/127). Intracranial calcification was identified in 89.4%(101/113) of the patients. Duration is an independent predictive factor (OR=1.483, P=0.011) for intracranial calcification. All the patients were treated with calcium and vitamin D or its metabolites. Hypercalciuria was associated with serum calcium (P=0.016). Conclusions: Carpopedal spasm and seizures were the main manifestations of childhood- and adolescent- onset hypoparathyroidism. Calcium and vitamin D or its metabolites are effective. Monitoring the concentration of serum and urinary calcium is of highly importance for the prevention of hypercalciuria.

In vivo anti-tumor activity of the PARP inhibitor niraparib in homologous recombination deficient and proficient ovarian carcinoma

OBJECTIVE

Poly(ADP-ribose) polymerase (PARP) inhibitors have yielded encouraging responses in high-grade serous ovarian carcinomas (HGSOCs), but the optimal treatment setting remains unknown. We assessed the effect of niraparib on HGSOC patient-derived xenograft (PDX) models as well as the relationship between certain markers of homologous recombination (HR) status, including BRCA1/2 mutations and formation of RAD51 foci after DNA damage, and response of these PDXs to niraparib in vivo.

METHODS

Massively parallel sequencing was performed on HGSOCs to identify mutations contributing to HR deficiency. HR pathway integrity was assessed using fluorescence microscopy-based RAD51 focus formation assays. Effects of niraparib (MK-4827) on treatment-naïve PDX tumor growth as monotherapy, in combination with carboplatin/paclitaxel, and as maintenance therapy were assessed by transabdominal ultrasound. Niraparib responses were correlated with changes in levels of poly(ADP-ribose), PARP1, and repair proteins by western blotting.

RESULTS

Five PDX models were evaluated in vivo. Tumor regressions were induced by single-agent niraparib in one of two PDX models with deleterious BRCA2 mutations and in a PDX with RAD51C promoter methylation. Diminished formation of RAD51 foci failed to predict response, but Artemis loss was associated with resistance. Niraparib generally failed to enhance responses to carboplatin/paclitaxel chemotherapy, but maintenance niraparib therapy delayed progression in a BRCA2-deficient PDX.

CONCLUSIONS

Mutations in HR genes are neither necessary nor sufficient to predict response to niraparib. Assessment of repair status through multiple complementary assays is needed to guide PARP inhibitor therapy, design future clinical trials and identify ovarian cancer patients most likely to benefit from PARP inhibition.

Constitutive BAK activation as a determinant of drug sensitivity in malignant lymphohematopoietic cells

Mitochondrial outer membrane permeabilization (MOMP), a key step in the intrinsic apoptotic pathway, is incompletely understood. Current models emphasize the role of BH3-only BCL2 family members in BAX and BAK activation. Here we demonstrate concentration-dependent BAK autoactivation under cell-free conditions and provide evidence that this autoactivation plays a key role in regulating the intrinsic apoptotic pathway in intact cells. In particular, we show that up to 80% of BAK (but not BAX) in lymphohematopoietic cell lines is oligomerized and bound to anti-apoptotic BCL2 family members in the absence of exogenous death stimuli. The extent of this constitutive BAK oligomerization is diminished by BAK knockdown and unaffected by BIM or PUMA down-regulation. Further analysis indicates that sensitivity of cells to BH3 mimetics reflects the identity of the anti-apoptotic proteins to which BAK is constitutively bound, with extensive BCLXL•BAK complexes predicting navitoclax sensitivity, and extensive MCL1•BAK complexes predicting A1210477 sensitivity. Moreover, high BAK expression correlates with sensitivity of clinical acute myelogenous leukemia to chemotherapy, whereas low BAK levels correlate with resistance and relapse. Collectively, these results inform current understanding of MOMP and provide new insight into the ability of BH3 mimetics to induce apoptosis without directly activating BAX or BAK.

MLN4924 induces Noxa upregulation in acute myelogenous leukemia and synergizes with Bcl-2 inhibitors

MLN4924 (pevonedistat), an inhibitor of the Nedd8 activating enzyme (NAE), has exhibited promising clinical activity in acute myelogenous leukemia (AML). Here we demonstrate that MLN4924 induces apoptosis in AML cell lines and clinical samples via a mechanism distinct from those observed in other malignancies. Inactivation of E3 cullin ring ligases (CRLs) through NAE inhibition causes accumulation of the CRL substrate c-Myc, which transactivates the PMAIP1 gene encoding Noxa, leading to increased Noxa protein, Bax and Bak activation, and subsequent apoptotic changes. Importantly, c-Myc knockdown diminishes Noxa induction; and Noxa siRNA diminishes MLN4924-induced killing. Because Noxa also neutralizes Mcl-1, an anti-apoptotic Bcl-2 paralog often upregulated in resistant AML, further experiments have examined the effect of combining MLN4924 with BH3 mimetics that target other anti-apoptotic proteins. In combination with ABT-199 or ABT-263 (navitoclax), MLN4924 exerts a synergistic cytotoxic effect. Collectively, these results provide new insight into MLN4924-induced engagement of the apoptotic machinery that could help guide further exploration of MLN4924 for AML.

Emerging understanding of Bcl-2 biology: Implications for neoplastic progression and treatment

Bcl-2, the founding member of a family of apoptotic regulators, was initially identified as the protein product of a gene that is translocated and overexpressed in greater than 85% of follicular lymphomas (FLs). Thirty years later we now understand that anti-apoptotic Bcl-2 family members modulate the intrinsic apoptotic pathway by binding and neutralizing the mitochondrial permeabilizers Bax and Bak as well as a variety of pro-apoptotic proteins, including the cellular stress sensors Bim, Bid, Puma, Bad, Bmf and Noxa. Despite extensive investigation of all of these proteins, important questions remain. For example, how Bax and Bak breach the outer mitochondrial membrane remains poorly understood. Likewise, how the functions of anti-apoptotic Bcl-2 family members such as eponymous Bcl-2 are affected by phosphorylation or cancer-associated mutations has been incompletely defined. Finally, whether Bcl-2 family members can be successfully targeted for therapeutic advantage is only now being investigated in the clinic. Here we review recent advances in understanding Bcl-2 family biology and biochemistry that begin to address these questions.

Casp8p41 generated by HIV protease kills CD4 T cells through direct Bak activation

HIV protease converts procaspase 8 into Casp8p41, which binds and activates Bak to induce cell death in infected CD4 T cells.

Previous studies have shown that human immunodeficiency virus (HIV) protease cleaves procaspase 8 to a fragment, termed Casp8p41, that lacks caspase activity but nonetheless contributes to T cell apoptosis. Herein, we show that Casp8p41 contains a domain that interacts with the BH3-binding groove of pro-apoptotic Bak to cause Bak oligomerization, Bak-mediated membrane permeabilization, and cell death. Levels of active Bak are higher in HIV-infected T cells that express Casp8p41. Conversely, targeted mutations in the Bak-interacting domain diminish Bak binding and Casp8p41-mediated cell death. Similar mutations in procaspase 8 impair the ability of HIV to kill infected T cells. These observations support a novel paradigm in which HIV converts a normal cellular constituent into a direct activator that functions like a BH3-only protein.

Poly(ADP-ribose) polymerase inhibitors sensitize cancer cells to death receptor-mediated apoptosis by enhancing death receptor expression

Recombinant human tumor necrosis factor-α-related apoptosis inducing ligand (TRAIL), agonistic monoclonal antibodies to TRAIL receptors, and small molecule TRAIL receptor agonists are in various stages of preclinical and early phase clinical testing as potential anticancer drugs. Accordingly, there is substantial interest in understanding factors that affect sensitivity to these agents. In the present study we observed that the poly(ADP-ribose) polymerase (PARP) inhibitors olaparib and veliparib sensitize the myeloid leukemia cell lines ML-1 and K562, the ovarian cancer line PEO1, non-small cell lung cancer line A549, and a majority of clinical AML isolates, but not normal marrow, to TRAIL. Further analysis demonstrated that PARP inhibitor treatment results in activation of the FAS and TNFRSF10B (death receptor 5 (DR5)) promoters, increased Fas and DR5 mRNA, and elevated cell surface expression of these receptors in sensitized cells. Chromatin immunoprecipitation demonstrated enhanced binding of the transcription factor Sp1 to the TNFRSF10B promoter in the presence of PARP inhibitor. Knockdown of PARP1 or PARP2 (but not PARP3 and PARP4) not only increased expression of Fas and DR5 at the mRNA and protein level, but also recapitulated the sensitizing effects of the PARP inhibition. Conversely, Sp1 knockdown diminished the PARP inhibitor effects. In view of the fact that TRAIL is part of the armamentarium of natural killer cells, these observations identify a new facet of PARP inhibitor action while simultaneously providing the mechanistic underpinnings of a novel therapeutic combination that warrants further investigation.

Contribution of Bcl-2 phosphorylation to Bak binding and drug resistance

Bcl-2 is phosphorylated on Ser(70) after treatment of cells with spindle poisons. On the basis of effects observed in cells overexpressing Bcl-2 S70E or S70A mutants, various studies have concluded that Ser(70) phosphorylation either enhances or diminishes Bcl-2 function. In the present study, the ability of phosphorylated Bcl-2, as well as the S70E and S70A mutants, to bind and neutralize proapoptotic Bcl-2 family members under cell-free conditions and in intact cells was examined in an attempt to resolve this controversy. Surface plasmon resonance indicated that phosphorylated Bcl-2, Bcl-2 S70E, and Bcl-2 S70A exhibit enhanced binding to Bim and Bak compared with unmodified Bcl-2. This enhanced binding reflected a readily detectable conformation change in the loop domain of Bcl-2. Furthermore, Bcl-2 S70E and S70A bound more Bak and Bim than wild-type Bcl-2 in pull-downs and afforded greater protection against several chemotherapeutic agents. Importantly, binding of endogenous Bcl-2 to Bim also increased during mitosis, when Bcl-2 is endogenously phosphorylated, and disruption of this mitotic Bcl-2/Bim binding with navitoclax or ABT-199, like Bcl-2 downregulation, enhanced the cytotoxicity of paclitaxel. Collectively, these results provide not only a mechanistic basis for the enhanced antiapoptotic activity of phosphorylated Bcl-2, but also an explanation for the ability of BH3 mimetics to enhance taxane sensitivity.

Farnesyltransferase inhibitor tipifarnib inhibits Rheb prenylation and stabilizes Bax in acute myelogenous leukemia cells

Although farnesyltransferase inhibitors have shown promising activity in relapsed lymphoma and sporadic activity in acute myelogenous leukemia, their mechanism of cytotoxicity is incompletely understood, making development of predictive biomarkers difficult. In the present study, we examined the action of tipifarnib in human acute myelogenous leukemia cell lines and clinical samples. In contrast to the Ras/MEK/ERK pathway-mediated Bim upregulation that is responsible for tipifarnib-induced killing of malignant lymphoid cells, inhibition of Rheb-induced mTOR signaling followed by dose-dependent upregulation of Bax and Puma occurred in acute myelogenous leukemia cell lines undergoing tipifarnib-induced apoptosis. Similar Bax and Puma upregulation occurred in serial bone marrow samples harvested from a subset of acute myelogenous leukemia patients during tipifarnib treatment. Expression of FTI-resistant Rheb M184L, like knockdown of Bax or Puma, diminished tipifarnib-induced killing. Further analysis demonstrated that increased Bax and Puma levels reflect protein stabilization rather than increased gene expression. In U937 cells selected for tipifarnib resistance, neither inhibition of signaling downstream of Rheb nor Bax and Puma stabilization occurred. Collectively, these results not only identify a pathway downstream from Rheb that contributes to tipifarnib cytotoxicity in human acute myelogenous leukemia cells, but also demonstrate that FTI-induced killing of lymphoid versus myeloid cells reflects distinct biochemical mechanisms downstream of different farnesylated substrates. (ClinicalTrials.gov identifier NCT00602771).

Enhanced permeation of single-file water molecules across a noncylindrical nanochannel

We utilize molecular dynamics simulations to study the effect of noncylindrical shapes of a nanochannel (which are inspired from the shape of real biological water nanochannels) on the permeation of single-file water molecules across the nanochannel. Compared with the cylindrical shape that has been tremendously adopted in the literature, the noncylindrical shapes play a crucial role in enhancing water permeation. Remarkably, the maximal enhancement ratio reaches a value of 6.28 (enhancement behavior). Meanwhile, the enhancement becomes saturated when the volume of the noncylindrical shape continues to increase (saturation behavior). The analysis of average diffusivity of water molecules helps to reveal the mechanism underlying the two behaviors whereas Poiseuille's law fails to explain them. These results pave a way for designing high-flow nanochannels and provide insight into water permeation across biological water nanochannels.

CXCR4 chemokine receptor signaling induces apoptosis in acute myeloid leukemia cells via regulation of the Bcl-2 family members Bcl-XL, Noxa, and Bak

The CXCR4 chemokine receptor promotes survival of many different cell types. Here, we describe a previously unsuspected role for CXCR4 as a potent inducer of apoptosis in acute myeloid leukemia (AML) cell lines and a subset of clinical AML samples. We show that SDF-1, the sole ligand for CXCR4, induces the expected migration and ERK activation in the KG1a AML cell line transiently overexpressing CXCR4, but ERK activation did not lead to survival. Instead, SDF-1 treatment led via a CXCR4-dependent mechanism to apoptosis, as evidenced by increased annexin V staining, condensation of chromatin, and cleavage of both procaspase-3 and PARP. This SDF-1-induced death pathway was partially inhibited by hypoxia, which is often found in the bone marrow of AML patients. SDF-1-induced apoptosis was inhibited by dominant negative procaspase-9 but not by inhibition of caspase-8 activation, implicating the intrinsic apoptotic pathway. Further analysis showed that this pathway was activated by multiple mechanisms, including up-regulation of Bak at the level of mRNA and protein, stabilization of the Bak activator Noxa, and down-regulation of antiapoptotic Bcl-XL. Furthermore, adjusting expression levels of Bak, Bcl-XL, or Noxa individually altered the level of apoptosis in AML cells, suggesting that the combined modulation of these family members by SDF-1 coordinates their interplay to produce apoptosis. Thus, rather than mediating survival, SDF-1 may be a means to induce apoptosis of CXCR4-expressing AML cells directly in the SDF-1-rich bone marrow microenvironment if the survival cues of the bone marrow are disrupted.

Phosphatidylserine exposure during apoptosis reflects bidirectional trafficking between plasma membrane and cytoplasm

Phosphatidylserine (PS) exposure on the external leaflet of the plasma membrane is widely observed during apoptosis and forms the basis for the annexin V binding assay to detect apoptotic cell death. Current efforts to explain PS exposure focus on two potential mechanisms, activation of a phospholipid scramblase or calcium-mediated trafficking of lysosomes to the cell surface. Here, we provide evidence that apoptotic PS exposure instead reflects bidirectional trafficking of membrane between the cell surface and cytoplasm. Using a series of cell lines, some of which expose large amounts of PS during apoptosis and some of which do not, we demonstrate that accumulation of plasma membrane-derived cytoplasmic vesicles in a dynamin-, clathrin- and Cdc42-independent manner is a previously undescribed but widely occurring feature of apoptosis. The apoptotic exposure of PS occurs when these vesicles traffic back to cell surface in a calcium-dependent process that is deficient in a substantial fraction of human cancer cell lines. These observations provide a new model for PS externalization during apoptosis and simultaneously identify an altered step that accounts for the paucity of apoptotic PS exposure in many cell lines.

Bak Conformational Changes Induced by Ligand Binding: Insight into BH3 Domain Binding and Bak Homo-Oligomerization

Recently we reported that the BH3-only proteins Bim and Noxa bind tightly but transiently to the BH3-binding groove of Bak to initiate Bak homo-oligomerization. However, it is unclear how such tight binding can induce Bak homo-oligomerization. Here we report the ligand-induced Bak conformational changes observed in 3D models of Noxa·Bak and Bim·Bak refined by molecular dynamics simulations. In particular, upon binding to the BH3-binding groove, Bim and Noxa induce a large conformational change of the loop between helices 1 and 2 and in turn partially expose a remote groove between helices 1 and 6 in Bak. These observations, coupled with the reported experimental data, suggest formation of a pore-forming Bak octamer, in which the BH3-binding groove is at the interface on one side of each monomer and the groove between helices 1 and 6 is at the interface on the opposite side, initiated by ligand binding to the BH3-binding groove.

Death receptor 5 signaling promotes hepatocyte lipoapoptosis

Nonalcoholic steatohepatitis is characterized by hepatic steatosis, elevated levels of circulating free fatty acids (FFA), endoplasmic reticulum (ER) stress, and hepatocyte lipoapoptosis. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) death receptor 5 (DR5) is significantly elevated in patients with nonalcoholic steatohepatitis, and steatotic hepatocytes demonstrate increased sensitivity to TRAIL-mediated cell death. Nonetheless, a role for TRAIL and/or DR5 in mediating lipoapoptotic pathways is unexplored. Here, we examined the contribution of DR5 death signaling to lipoapoptosis by free fatty acids. The toxic saturated free fatty acid palmitate induces an increase in DR5 mRNA and protein expression in Huh-7 human hepatoma cells leading to DR5 localization into lipid rafts, cell surface receptor clustering with subsequent recruitment of the initiator caspase-8, and ultimately cellular demise. Lipoapoptosis by palmitate was not inhibited by a soluble human recombinant DR5-Fc chimera protein suggesting that DR5 cytotoxic signaling is ligand-independent. Hepatocytes from murine TRAIL receptor knock-out mice (DR(-/-)) displayed reduced palmitate-mediated lipotoxicity. Likewise, knockdown of DR5 or caspase-8 expression by shRNA technology attenuated palmitate-induced Bax activation and apoptosis in Huh-7 cells, without altering induction of ER stress markers. Similar observations were verified in other cell models. Finally, knockdown of CHOP, an ER stress-mediated transcription factor, reduced DR5 up-regulation and DR5-mediated caspase-8 activation upon palmitate treatment. Collectively, these results suggest that ER stress-induced CHOP activation by palmitate transcriptionally up-regulates DR5, likely resulting in ligand-independent cytotoxic signaling by this death receptor.

Wnt/β-catenin signaling regulates MAPK and Akt1 expression and growth of hepatocellular carcinoma cells

In hepatocellular carcinoma (HCC), Wnt/β-catenin, Ras/MAPK and PI3K/AKT signaling pathways form a complex network and play important roles during HCC genesis and development. To study their relationship and the influence on cell growth, the siRNA directed against β-catenin was transfected into HCC HepG2 cells. β-catenin mRNA and protein levels were measured respectively at various times by RT-PCR and Western blot. Furthermore, HCC cell growth was measured by MTT assay. Finally, MAPK family and Akt1 protein levels were also measured by Western blot. After the transfection, β-catenin mRNA levels were markedly inhibited at 24 h and increased gradually at 48, 72 and 96 h; β-catenin protein levels decreased gradually at 24, 48 and 72 h and slightly increased at 96 h. HCC cell growth was inhibited from 24-72 h, but this inhibition decreased at 96 h. ERK1/2 (p42/p44 MAPK), JNK/SAPK, p38 MAPK, and Akt1 protein levels showed no change following transfection, while their phosphorylated protein levels showed changes. Thus, siRNA directed against β-catenin markedly decreased β-catenin gene expression and inhibited cell growth. Wnt/β-catenin signaling pathway might regulate Ras/MAPK and PI3K/Akt signaling pathways through regulation of the phosphorylation state of ERK1/2, JNK/SAPK and Akt1 protein in HCC HepG2 cells. These pathways might compensate for the inhibitory effect of β-catenin, thereby affecting tumor cell growth and others downstream factors.

Transient binding of an activator BH3 domain to the Bak BH3-binding groove initiates Bak oligomerization

The mechanism by which the proapoptotic Bcl-2 family members Bax and Bak release cytochrome c from mitochondria is incompletely understood. In this paper, we show that activator BH3-only proteins bind tightly but transiently to the Bak hydrophobic BH3-binding groove to induce Bak oligomerization, liposome permeabilization, mitochondrial cytochrome c release, and cell death. Analysis by surface plasmon resonance indicated that the initial binding of BH3-only proteins to Bak occurred with similar kinetics with or without detergent or mitochondrial lipids, but these reagents increase the strength of the Bak-BH3-only protein interaction. Point mutations in Bak and reciprocal mutations in the BH3-only proteins not only confirmed the identity of the interacting residues at the Bak-BH3-only protein interface but also demonstrated specificity of complex formation in vitro and in a cellular context. These observations indicate that transient protein-protein interactions involving the Bak BH3-binding groove initiate Bak oligomerization and activation.

Context-dependent Bcl-2/Bak interactions regulate lymphoid cell apoptosis

The release of cytochrome c from mitochondria, which leads to activation of the intrinsic apoptotic pathway, is regulated by interactions of Bax and Bak with antiapoptotic Bcl-2 family members. The factors that regulate these interactions are, at the present time, incompletely understood. Recent studies showing preferences in binding between synthetic Bcl-2 homology domain 3 and antiapoptotic Bcl-2 family members in vitro have suggested that the antiapoptotic proteins Mcl-1 and Bcl-x(L), but not Bcl-2, restrain proapoptotic Bak from inducing mitochondrial membrane permeabilization and apoptosis. Here we show that Bak protein has a much higher affinity than the 26-amino acid Bak Bcl-2 homology domain 3 for Bcl-2, that some naturally occurring Bcl-2 allelic variants have an affinity for full-length Bak that is only 3-fold lower than that of Mcl-1, and that endogenous levels of these Bcl-2 variants (which are as much as 40-fold more abundant than Mcl-1) restrain part of the Bak in intact lymphoid cells. In addition, we demonstrate that Bcl-2 variants can, depending on their affinity for Bak, substitute for Mcl-1 in protecting cells. Thus, the ability of Bcl-2 to protect cells from activated Bak depends on two important contextual variables, the identity of the Bcl-2 present and the amount expressed.

Apoptosis-associated caspase activation assays

Caspases are aspartate-directed cysteine proteases that cleave a diverse group of intracellular substrates to contribute to various manifestations of apoptosis. These proteases are synthesized as inactive precursors and are activated as a consequence of signaling induced by a wide range of physiological and pathological stimuli. Caspase activation can be detected by measurement of catalytic activity, immunoblotting for cleavage of their substrates, immunolabeling using conformation-sensitive antibodies or affinity labeling followed by flow cytometry or ligand blotting. Here we describe methods for each of these assays, identify recent improvements in these assays and outline the strengths and limitations of each approach.

An investigation of a possible role for mitochondrial nuclease in apoptosis

Since mitochondrial factors have been implicated in apoptosis, experiments were designed to assess whether or not the potent mitochondrial nuclease could be one of these factors. Nuclei isolated by two different methods were found to contain mitochondrial nuclease in masked form. This nuclease was released by treatment with the non-ionic detergent NP-40 and rendered trypsin-sensitive. It was not removed appreciably from the nuclei by washing and sedimentation of the nuclei through a sucrose cushion. Levels of the mitochondrial nuclease were followed during drug-induced apoptosis. Time courses of apoptosis in cultures of HL-60 cells were monitored by flow cytometry of propidium iodide-stained cells and by agarose gel electrophoresis of extracted DNA. Changes in the inner mitochondrial transmembrane potential were monitored by flow cytometry of chloromethyl-X-Rosamine-stained cells. Apoptosis was induced by treatment with either the chemotherapeutic agent etoposide (VP-16 at 10 microM) over an 8 h period or with the anti-rheumatic agent hydroxychloroquine (HCQ at 0.28 mM) over a 24 h period. These two drugs likely act in different pathways of apoptosis. VP-16 caused loss of the mitochondrial transmembrane potential 1.0-1.5 h before apoptosis was detected. On the other hand, treatment with HCQ caused these processes to occur in parallel possibly indicating that the mitochondrial changes are secondary events. No losses of masked mitochondrial nuclease were detected with either drug treatment during the course of apoptosis. HL-60 mitochondrial DNA was also not degraded during apoptosis induced by either agent. These observations likely explain why the mitochondrial DNA is not degraded and make it unlikely that mitochondrial nuclease plays any role in vivo in chromatin DNA fragmentation.

Lack of correlation between caspase activation and caspase activity assays in paclitaxel-treated MCF-7 breast cancer cells

MCF-7 human breast cancer cells are widely utilized to study apoptotic processes. Recent studies demonstrated that these cells lack procaspase-3. In the present study, caspase activation and activity were examined in this cell line after treatment with the microtubule poison paclitaxel. When cells were harvested 72 h after the start of a 24-h treatment with 100 nm paclitaxel, 37 +/- 5% of the cells were nonadherent and displayed apoptotic morphological changes. Although mitochondrial cytochrome c release and caspase-9 cleavage were detectable by immunoblotting, assays of cytosol and nuclei prepared from the apoptotic cells failed to demonstrate the presence of activity that cleaved the synthetic caspase substrates LEHD-7-amino-4-trifluoromethylcoumarin (LEHD-AFC), DEVD-AFC, and VEID-AFC. Likewise, the paclitaxel-treated MCF-7 cells failed to cleave a variety of caspase substrates, including lamin A, beta-catenin, gelsolin, protein kinase Cdelta, topoisomerase I, and procaspases-6, -8, and -10. Transfection of MCF-7 cells with wild type procaspase-3 partially restored cleavage of these polypeptides but did not result in detectable activities that could cleave the synthetic caspase substrates. Immunoblotting revealed that caspase-9, and -3, which were proteolytically cleaved in paclitaxel-treated MCF-7/caspase-3 cells, were sequestered in a salt-resistant sedimentable fraction rather than released to the cytosol. Immunofluorescence indicated large cytoplasmic aggregates containing cleaved caspase-3 in these apoptotic cells. These observations suggest that sequestration of caspases can occur in some model systems, causing tetrapeptide-based activity assays to underestimate the amount of caspase activation that has occurred in situ.

[Study of normal range of speed of sound in tibia in Beijing area]

OBJECTIVE

To study the normal reference value of adult tibial speed of sound (tibia SOS) in Beijing region.

METHODS

951 normal volunteers (male/female = 461/490) were included in this study. Speed of sound were measured in the middle of tibia by ultrasound scan (Sound Scan 2000, Myrid, Isereal). According to their gender and age, all subjects were divided into different subgroup by 10 year-age period.

RESULTS

The peak value of SOS presented in 30-39 years period in both male and female. The peak value was higher in males than in females. After reach the peak value, the tibial SOS begin to decline. The decreasing rate was fast in SOS were found at 50-59 period in female and over 50-59 years old in male. The tibia values of SOS of postmenopausal was obviously lower than that of premenopausal women. The relationship of menopausal duration and the values if tibial SOS was found to be a non-linear curve, which included 3 stages: the quick decrease, stabilization and further decrease.

CONCLUSION

The tibia values of SOS provides a kind of meaningful diagnostic criteria of osteoporosis.

[Polymorphism of parathyroid hormone gene and its association with bone mineral density of Han nationality women in Beijing area]

OBJECTIVE

To investigate the distribution of frequency of parathyroid hormone(PTH) gene polymorphisms in healthy adults of Han nationality in Beijing area and relationship between PTH genotypes and bone mineral density(BMD) in young and postmenopausal women.

METHODS

Polymorphism of PTH gene were detected by polymerase chain reaction restriction fragment length polymorphism(PCR-RFLP) of restriction enzyme Bst B1 in 270 subjects. If the site of enzyme Bst B1 existed, the PTH genotype was "B". On the contrary, if base mutation occurred, the genotype was "b". Some of the PTH genotypes were confirmed by DNA sequences analysis. Bone mineral density(BMD) was measured by dual-energy X-ray absorptiometry.

RESULTS

Genotype frequencies of BB, Bb, bb were 73.7%, 25.9%, and 0.4% respectively in adults of Beijing areas. The frequencies of RFLP alleles B, b were 86.7% and 13.3%. Beijing postmenopausal women frequencies of BB, Bb, bb were 67.1%, 32.2% and 0.7%. B, b alleles frequencies were 83.2% and 16.8%. We statistically compared bone mineral density at the lumbar 2-4, neck, wards triangle and trochanter major, there was no significant difference between BB and Bb genotype of young women and postmenopausal women groups. Otherwise, no obvious relationship was found between the BMD and PTH genotype in Beijing women.

CONCLUSIONS

PTH gene polymorphisms were not associated with BMD in Beijing women.

Clinical significance of TT virus in chronic hepatitis C

BACKGROUND AND AIMS

Much is still unknown about the clinical significance of TT virus (TTV), which has been reported as a candidate for non A-G hepatitis virus. The aim of this study was to clarify the clinical significance of TTV in patients coinfected with TTV and hepatitis C virus (HCV).

METHODS

The 95 subjects studied had chronic hepatitis C (CHC), and underwent interferon (IFN) therapy. TT Virus DNA was detected by using polymerase chain reaction. The nucleotide sequences were determined by using a dideoxy chain termination method. A phylogenetic tree was drawn up by using the neighbor-joining method.

RESULTS

TT Virus DNA was detected in 37.9% of patients with the use of an open reading frame 1 (ORF1) primer, and in 88.4% of patients by using a 5' untranslated region (5' UTR) primer. Using both sets of primers, no differences were found between TTV-DNA-positive and -negative subjects with CHC in the clinical findings. Serum TTV DNA was eradicated in 30.6% of patients with the ORF1 primer, and in 19.1% of patients with the 5' UTR primer at 6 months after the cessation of IFN therapy. The levels of TTV DNA before IFN therapy were significantly lower in the viral eradication group than in non-eradication group. The changes in alanine aminotransferase (ALT) concentrations were significantly correlated with changes in HCV-RNA in CHC patients with TTV. Moreover, there was no correlation between the changes in TTV DNA and the course of ALT.

CONCLUSION

Hepatocellular injury in patients with chronic hepatitis who are coinfected with HCV and TTV appears to primarily be caused by HCV and is less attributable to TTV.

Caspase-3 activates endo-exonuclease: further evidence for a role of the nuclease in apoptosis

Single-strand DNase and poly rAase, activities characteristic of endo-exonuclease, were co-activated in nuclear fractions of HL-60 cells by caspase-3. Activation was accompanied by cleavages of large soluble polypeptides (130-185 kDa) and a 65 kDa inactive chromatin-associated polypeptide related to the endo-exonuclease of Neurospora crassa as detected on immunoblots. The major products seen in vitro were a 77 kDa soluble polypeptide and an active chromatin-associated 34 kDa polypeptide. When HL-60 cells were induced to undergo apoptosis by treating with 50 microM etoposide (VP-16) for 4 hours, 77 kDa and 40 kDa polypeptides accumulated in nuclear fractions. Chromatin DNA fragmentation activity was also activated in cytosol and nuclear extract either by pre-treating the cells in vivo with VP-16 or by treating the cytosol in vitro with caspase-3 or dATP and cytochrome c. Endo-exonuclease activated by caspase-3 in cytosol-derived fractions augmented chromatin DNA fragmentation activity in vitro. Endo-exonuclease is proposed to act in vivo in conjunction with the caspase-activated DNase (CAD) to degrade chromatin DNA during apoptosis of HL-60 cells.

Causes of anorexia in untreated hyperthyroidism: a prospective study

Seventeen consecutive patients (mean (SD) 46 (11) years) with untreated hyperthyroidism and anorexia and 29 patients (35 (9) years) with untreated hyperthyroidism without anorexia were studied. The study was conducted at the thyroid clinic of the PUMC Hospital, Beijing, China from March to August 1997. The patients' ages, serum free calcium, liver function and emotional state, specifically the level of anxiety (using the self anxiety scale, Chinese version), were compared before and/or after antithyroid drug treatment in the two groups. This prospective study suggested that the causes of anorexia in untreated hyperthyroidism are complicated. Older age, abnormal liver function, and the level of anxiety are significantly related to anorexia in untreated hyperthyroidism, but hypercalcaemia was not confirmed to be related to anorexia in the study.

Iatrogenic GB virus C/hepatitis G virus infection in an area endemic for hepatitis C virus

GB virus C/hepatitis G virus (GBV-C/HGV) is reported to be transmitted by blood products. This study reports infection with GBV-C/HGV from Area-O of town T, an area of high prevalence of antibody to hepatitis C virus (anti-HCV). Four hundred and thirty-five inhabitants of Area-O in town T were examined. Three hundred and forty-three inhabitants of Area-H in town T (where differences of age or sex are not markedly different to Area-O) were studied as controls. We investigated the virus markers and conducted a survey of life history in both areas. The seroprevalence of anti-HCV and GBV-C/HGV markers in Area-O was 17.7% and 11.7%, significantly higher than in Area-H (1.5% and 4.4%). The prevalence of GBV-C/HGV markers was significantly higher in the anti-HCV-positive group than in the sero-negative group. Anti-HCV- or GBV-C/HGV positive subjects tended to have a history of intravenous medications at hospital C in town T, suggesting iatrogenic infection through insufficient sterilization of needles and/or syringes.

Caspase-3-dependent and caspase-3-independent pathways leading to chromatin DNA fragmentation in HL-60 cells

Apoptosis induced by etoposide (VP-16) in HL-60 cells was confirmed to be caspase-dependent. It was fully inhibited by the broad-spectrum caspase inhibitor Z-VAD-fmk. However, the caspase-3-specific inhibitor Z-DEVDfmk only partially inhibited apoptosis. This indicated that a second caspase is required in vivo for full activation of the apoptotic nucease CAD. Aurin tricarboxylic acid (ATA) did not inhibit VP-16-induced apoptosis. In contrast, apoptosis induced by hydroxychloroquine (HCQ) in HL-60 cells was caspase-3 independent and was fully inhibited by ATA. Thus, CAD does not appear to be involved in chromatin DNA degradation in this case. A second apoptotic nuclease is postulated to degrade the DNA, likely endo- exonuclease, an abundant nuclear enzyme that acts on both DNA and RNA and is present in latent form. HCQ, but not VP-16, stimulated DNA degradation ("laddering") in isolated nuclei. This indicates that the drug can act directly in the nuclei to trigger activation of the second latent apoptotic nuclease.

GB virus C infection: clinical significance

GB virus C (GBV-C) RNA positivity rates were examined in serum specimens from 231 patients with liver disease (23 patients with hepatitis B, 175 patients with hepatitis C, five patients with hepatitis B virus plus hepatitis C virus coinfection, and 28 patients with non-A, non-B, non-C hepatitis) to clarify the clinical significance of this virus. GBV-C RNA was detected in none of 12 patients with fulminant hepatitis, one of two patients with acute hepatitis positive for hepatitis B surface antigen and one of four patients with acute non-A, non-B, non-C hepatitis. Pathogenetic involvement of GBV-C was suspected in some patients in the latter group. Among patients with the non-B, non-C type of chronic disease, one of seven with cirrhosis (14%) and none with chronic hepatitis or hepatocellular carcinoma were GBV-C-positive. In chronic hepatitis C patients who had received interferon treatment, no difference was found in clinical findings, alanine aminotransferase (ALT) concentrations, histology or response to interferon between 11 patients who were GBV-C RNA-positive and 101 patients who were GBV-C RNA-negative. Moreover, changes in ALT after interferon therapy showed no relation to positivity for GBV-C RNA. On the basis of these findings, GBV-C appears to be an unlikely cause of initiation or progression of chronic hepatic diseases.

Primary biliary cirrhosis associated with membranous glomerulonephritis

A 33-year-old woman was admitted to our department for evaluation of liver dysfunction and proteinuria. A liver biopsy specimen showed ductular proliferation and moderate portal fibrosis indicating stage II primary biliary cirrhosis. A renal biopsy specimen showed mild to moderate mesangial cell proliferation without crescent formation or interstitial nephritis. Immunofluorescent staining revealed deposition of immunoglobulin G (IgG), third component of complement (C3), and Clq on glomerular basement membranes. The findings indicated stage I membranous glomerulonephritis. Administration of ursodesoxycholic acid together with prednisolone, azathioprine, and dipyridamole decreased proteinuria and improved cholestatic liver dysfunction.

Nitric oxide synthase containing neurons in the ventral lateral geniculate of the rat project to the optic pretectal nuclei

We combined fluorescent tracing with immunohistochemistry to examine nitric oxide synthase (NOS) containing neurons in the rat ventral lateral geniculate nucleus (vLGN). NOS immunopositive neurons in vLGN had a similar appearance to previously described NADPH-d positive neurons. The majority (96%) of the NOS immunopositive neurons in vLGN projected to the pretectal nuclei and these represented 16% of all the vLGN neurons that project to the pretectal nuclei. No NOS immunopositive neurons projected to the superior colliculus. Co-localization of NADPH-d and gamma-aminobutyric acid (GABA) has been reported in vLGN neurons but we found few cells containing both NOS and GABA.

Ultrastructural localization of nitric oxide synthase immunoreactivity in the cat ventrobasal complex

This study describes the ultrastructural localization of nitric oxide synthase (NOS) immunoreactivity in the cat ventrobasal complex. NOS immunoreactivity was found in the cell bodies and dendrites of local circuit neurons and in vesicle-containing profiles. The vesicle-containing profiles could be divided into two classes, those of dendritic origin (presynaptic dendrite boutons) and those of axonal origin. The NOS labelled axon terminals varied in size and packing density and were principally located in the extra-glomerular neuropil. These boutons presented a range of morphologies and it was not possible to determine the probable source based on morphological criteria. The NOS immunoreactive presynaptic dendrite boutons were found both within and outside glomeruli and established both pre- and post-synaptic relationships with other elements. Post-embedding GABA immunocytochemistry showed that some NOS immunoreactive axonal boutons and presynaptic dendrites were also immunopositive for GABA. This finding suggests that some of the NOS labelled axonal boutons are of local circuit neuron origin. These results suggest that local circuit neurons in the cat ventrobasal complex might be involved in specific, short range interactions using GABA and longer, more global interactions using nitric oxide.

Induction of apoptosis in peripheral blood lymphocytes following treatment in vitro with hydroxychloroquine

OBJECTIVE

Defective regulation of apoptosis may be central to the development of autoimmune disorders. This study investigated the possibility that the antirheumatic effect of hydroxycholoroquine (HCQ) may be achieved by up-regulation of apoptosis.

METHODS

Peripheral blood lymphocytes collected from normal controls and patients with systemic lupus erythematosus (SLE) were cultured in the presence or absence of a range of concentrations of HCQ. Cells undergoing apoptosis were identified by several standard methods, including morphologic changes, DNA fragmentation, and flow cytometry. For some experiments, lymphocytes were simultaneously stained with antibodies to T cell surface markers and with propidium iodide for dual-stain flow cytometric studies.

RESULTS

HCQ was able to induce apoptosis in peripheral blood lymphocytes in a dose- and time-dependent manner. HCQ induced these changes in all T cell subpopulations studied. There was no significant difference between the controls and patients with SLE in terms of the percentage of apoptotic cells detected following treatment with HCQ.

CONCLUSION

The present study demonstrated that HCQ induces apoptosis in peripheral blood lymphocytes, which leads to the speculation that HCQ may exert its antirheumatic effect through this mechanism.

Noradrenergic input to nociceptive modulatory neurons in the rat rostral ventromedial medulla

Within the rostral ventromedial medulla (RVM), there are two classes of putative pain modulation neurons: ON cells and OFF cells, which respectively burst or pause prior to withdrawal reflexes elicited by noxious stimulation. Alpha-adrenergic agonists injected into the RVM produce changes in the latency of spinal nocifensive reflexes and, when iontophoretically applied, alter the firing of RVM ON but not OFF cells. To provide further information about the contribution of norepinephrine to RVM neuron function, we analyzed the distribution of tyrosine hydroxylase immunoreactive (TH-ir) appositions upon RVM ON and OFF cells. In the lightly anesthetized rat, seven ON and five OFF cells were identified by changes in their discharge rate in relation to nociceptive withdrawal reflexes and were labeled by intracellular injection of neurobiotin. Sections containing labeled cells were visualized by using avidin conjugated to a Texas Red fluorophore. Tissue with labeled cells was subsequently processed for TH-ir by using a Bodipy fluorophore conjugated secondary antibody. The distribution of the Bodipy-labeled fibers and terminals upon the Texas Red-labeled neurons was mapped using a confocal laser-scanning microscope. All the labeled neurons exhibited close TH-ir appositions. Appositions were of two types: swellings and fibers. Although the numbers and density of appositions varied among the cells, there were no consistent differences that correlated with physiological properties. Thus the overall density of appositions for ON cells (29.0 +/- 22.2 x 10(4) microns2) did not differ significantly from that for OFF cells (25.4 +/- 22.2 x 10(4) microns2). Tyrosine hydroxylase immunoreactive (TH-ir) appositions upon ON and OFF cells varied with their location along the dorso-ventral axis with more ventral neurons having a greater density of TH-ir swelling-type appositions. In a separate study, TH-ir and dopamine-beta-hydroxylase-like immunoreactivity (DBH-ir) were mapped in the same sections by using confocal microscopy. Nearly 97% of the TH-ir profiles co-localized with DBH-ir. These observations provide evidence that both ON and OFF cells in the RVM are targeted by noradrenergic inputs.

Transneuronal changes of the inhibitory circuitry in the macaque somatosensory thalamus following lesions of the dorsal column nuclei

The inhibitory circuitry of the ventroposterolateral nucleus (VPL) of the macaque somatosensory thalamus was analyzed in normal animals and in those surviving for a few days or several weeks following a unilateral lesion of the cuneate nucleus, the source of medial lemniscal (ML) axons carrying information from the contralateral upper extremity. Inhibitory synaptic terminals in the VPL were defined as those that contain flattened or pleomorphic synaptic vesicles and that can be shown to be immunoreactive for gamma-aminobutyric acid (GABA). There are two types of these profiles: F axon terminals that arise from neurons of the thalamic reticular nucleus, and perhaps from VPL local circuit neurons (LCNs); and the dendritic appendages of LCNs that form presynaptic dendrites (PSDs). ML terminals normally have extensive synaptic interactions with PSDs but not with F axon terminals. Electron microscopic analyses revealed that cuneatus lesions resulted in a rapid loss of ML terminals and a statistically significant reduction in both F and PSD synaptic profiles. Confocal scanning microscopy also demonstrated a profound loss of GABA immunoreactivity in the deafferented VPL. These changes persisted for more than 20 weeks, without any evidence of reactive synaptogenesis of surviving sensory afferents or of inhibitory synapses. The changes in GABA circuitry are transneuronal, and the possible mechanisms that may underlie them are discussed. It is suggested that the altered GABAergic circuitry of the VPL in the monkey may serve as a model for understanding changes in somatic sensation in the human following peripheral or central deafferentation.

Nitric oxide synthase immunoreactivity distinguishes a sub-population of GABA-immunoreactive neurons in the ventrobasal complex of the cat

This study describes the presence of nitric oxide synthase (NOS-ir) immunoreactive neurons in the thalamic ventrobasal complex of the cat. NOS-ir is co-localized with gamma-aminobutyric acid (GABA-ir) in a subset of small neurons identified as local circuit neurons in previous studies. The double labeled neurons are further identified by a larger soma diameter when compared to GABA-ir only neurons. All NOS-ir somata exhibit GABA-ir but none exhibit immunoreactivity to calbindin.

Mast cells expressing chymase but not tryptase can be derived by culturing human progenitors in conditioned medium obtained from a human mastocytosis cell strain with c-kit ligand

Human mast cells (MC) were derived from umbilical cord blood and bone marrow progenitors cultured in the presence of a conditioned medium from a human mastocytosis cell strain and recombinant human kit ligand. MCs were studied using a sequential double immunoenzymatic analysis to determine the heterogeneity of expression of tryptase and chymase, two MC-specific proteases. The conditioned medium and kit ligand promoted the development of distinct MC subtypes from bone marrow and umbilical cord blood progenitors. kit ligand induced MC from umbilical cord blood predominantly of two immunophenotypes, MCT positive for tryptase but negative for chymase, and MCTC positive for tryptase and chymase. In contrast, the conditioned medium induced MC subtype MCTC and a third subtype, MCC, positive for chymase but negative for tryptase from both bone marrow and umbilical cord blood progenitors. In situ hybridization analyses confirmed the existence of a chymase-positive, tryptase-negative human MC in the culture. In umbilical cord blood cultures supplemented with both conditioned medium and kit ligand, the number of MCC cells was up-regulated from 2.7 to 34.0% of the total cells in the culture. In contrast, the number of MCT cells declined from 54.3 to 21.5% on day 49 of culture. In bone marrow cultures supplemented with conditioned medium alone, the MCC subtype represented 100% of the MCs on day 10 of culture. This study clearly demonstrates that a third type of MC, MCC, expressing chymase without concomitant expression of tryptase can be induced in vitro from normal human progenitors. In addition, it shows that tryptase and chymase, two MC-specific proteases, can be differentially expressed in in vitro derived human MCs by changing the cytokine combination of the culture.