EquiPrEP: An implementation science protocol for promoting equitable access and uptake of long-acting injectable HIV pre-exposure prophylaxis (LAI-PrEP)

BACKGROUND

Long-acting injectable HIV pre-exposure prophylaxis (LAI-PrEP) was approved by the U.S. Food and Drug Administration in December 2021. This initial phase of implementation represents a prime opportunity to ensure equitable LAI-PrEP provision to communities often underrepresented in PrEP care before disparities in access and uptake emerge. Herein, we describe the EquiPrEP Project which utilizes an equity-oriented implementation science framework to optimize LAI-PrEP rollout in an urban safety-net clinic in New York City.

METHODS

The primary objectives of this project are to: (1) increase LAI-PrEP initiation overall; (2) increase uptake among groups disproportionately impacted by the HIV epidemic; (3) preserve high PrEP retention while expanding use; and (4) identify barriers and facilitators to LAI-PrEP use. EquiPrEP will enroll 210 PrEP-eligible participants into LAI-PrEP care with planned follow-up for one year. We will recruit from the following priority populations: Black and/or Latine men who have sex with men, Black and/or Latine cisgender women, and transgender women and nonbinary individuals. To evaluate implementation of LAI-PrEP, we will utilize equity-focused iterations of the Reach, Effectiveness, Adoption, Implementation, Maintenance (RE-AIM) framework and the Consolidated Framework for Implementation Research (CFIR), in addition to longitudinal surveys and qualitative interviews.

DISCUSSION

Novel LAI-PrEP formulations carry tremendous potential to revolutionize the field of HIV prevention. Implementation strategies rooted in equity are needed to ensure that marginalized populations have access to LAI-PrEP and to address the structural factors that hinder initiation and retention in care.

Critical Elements of an Mpox Vaccination Model at the Largest Public Health Hospital System in the United States

In the spring of 2022, mpox spread to non-endemic countries, including the United States. In New York City (NYC), vaccine demand grew as quickly as case counts. With the leadership of the Regional Emerging Special Pathogens Treatment Center (RESPTC) at NYC Health and Hospitals/Bellevue (NYC H+H)-part of the largest public hospital system in the United States-an innovative vaccination model was established that overcame challenges involving health inequities, inadequate access, and lack of vaccine uptake, to successfully administer JYNNEOS vaccines to over 12,000 patients. Transmission has slowed since its peak in August 2022, which has been attributed to successful vaccination campaigns, infection-induced immunity, and behavioral changes among those at highest risk; however, a Centers for Disease Control and Prevention (CDC) assessment released on 4 April 2023 suggests jurisdictions with low vaccination levels (<35%) remain at risk for an mpox resurgence. Here, we summarize the critical aspects of our mpox vaccination model in NYC, which include integration into routine clinical care, prioritization of health equity, and reutilization of COVID-19 vaccination systems, to provide valuable insights for healthcare institutions as we move into the next stage of this ongoing outbreak.

Understanding the Relationship Between Antiviral Prescription Data and COVID-19 Incidence in New York City: A Retrospective Cohort Study

The coronavirus disease 2019 (COVID-19) pandemic has caused more than 675 million confirmed cases and nearly 7 million deaths worldwide [1]. While testing for COVID-19 was initially centered in health care facilities, with required reporting to health departments, it is increasingly being performed in the home with rapid antigen testing [2]. Most at-home tests are self-interpreted and not reported to a provider or health department, which could lead to delayed reporting or underreporting of cases [3]. As such, there is a strong possibility that reported cases may become a less reliable indicator of transmission over time.

The Role of a Tertiary Level Safety Net Hospital in New York City's 2022 Mpox Outbreak

Similar to the early phases of the COVID-19 pandemic, New York City was the national epicenter of the ongoing 2022 mpox (formerly monkeypox) outbreak. Cases quickly began to rise in July 2022, primarily in gay, bisexual, or other men who have sex with men. Tools in the form of a reliable diagnostic test, an effective vaccine, and a viable treatment option have been available from the onset, although logistically complex to roll out. The special pathogens program at NYC Health + Hospitals/Bellevue, the flagship facility for the largest public hospital system in the United States, collaborated with multiple departments within Bellevue, the hospital system, and the NYC Department of Health and Mental Hygiene, to swiftly establish ambulatory testing, immunizations, patient-centered inpatient care, and outpatient therapeutics. With the ongoing mpox outbreak, hospitals and local health departments must prepare a systemwide response to identify and isolate patients and provide high-quality care. Findings from our experience can help guide institutions in developing a multipronged, comprehensive response to the ongoing mpox outbreak.

1901. Utilizing Antiviral Prescription Data as a Predictor of Increasing COVID-19 Incidence: A Retrospective Study of Citywide Data

Background

COVID-19 has caused over 6 million deaths worldwide. While testing was initially centered in healthcare facilities with automatic reporting to health departments, it is increasingly being performed in the home with rapid antigen testing. Many at-home tests are self-interpreted and not typically reported.

In December 2021, nirmatrelvir/ritonavir and molnupiravir were authorized for the treatment of COVID-19 in high-risk patients. In New York City (NYC), these antivirals are available for free via pickup or home delivery, allowing for early expanded access. We sought to identify if prescribing of antivirals might act as an early indicator of increasing COVID-19 incidence in the setting of decreased case reporting.

Methods

Confirmed and probable COVID-19 tests are reported to the NYC Health Department. All pharmacies participating in the federal COVID-19 therapeutics program are required to report daily utilization data, which are made available to jurisdictions through the Tiberius platform. From December 27, 2021 to April 18, 2022, we analyzed citywide weekly case counts, using patients 65 years and over as a proxy for high-risk eligible patients, and weekly oral therapeutic prescription fills. We calculated weekly case rates and prescribing rates per 100,000 residents. Weekly case rates and prescription fill rates were trended to assess for concordance over time.

Results

During this period, 17,522 prescriptions were filled. Prescription fills and case rates were concordant until the weeks of February 28 and March 7, when an increase in fill rate was noted from the week prior (1.76 to 2.34 to 4.10), while reported case incidence continued to decrease (6.16 to 5.08 to 4.61). This discordance coincided with the emergence of the BA.2 subvariant in NYC. After these weeks, an uptick in case incidence was noted for the remainder of the study period, in concordance with prescription data.

Conclusion

Increasing rates of oral therapeutic prescribing could be an early indicator of increasing COVID-19 transmission. Limitations include the unclear impact of public and prescriber education efforts on prescribing trends. Next steps include exploring the addition of prescription data into modeling to predict trends in transmission as reported cases becomes a less reliable indicator.

Disclosures

Gabriel M. Cohen, MD, Daybreak Health: Advisor/Consultant|Daybreak Health: Board Member|Daybreak Health: Ownership Interest Andrew B. Wallach, MD, Pfizer: Advisor/Consultant.

HIV Diagnosis and the Clinical Course of COVID-19 Among Patients Seeking Care Within the New York City Public Hospital System During the Initial Pandemic Peak

Reports conflict on how HIV infection influences the clinical course of COVID-19. The New York City (NYC) public hospital system provides care for over 14,000 people with HIV, was central in responding to the COVID-19 pandemic, and is therefore in a unique position to evaluate the intersection of these concurrent infections. Retrospective chart review of patients presenting to NYC Health and Hospitals (NYC H+H) diagnosed with COVID-19 infection from March 1, 2020, through April 28, 2020, compared people living with HIV (PLWH) and a propensity-matched (PM) control group of patients without HIV to evaluate associations between HIV status and COVID-19 outcomes. Two hundred thirty-four PLWH presented for COVID-19 testing and 110 (47%) were diagnosed with COVID-19. Among 17,413 patients with COVID-19 and without HIV, 1:n nearest neighbor propensity score matching identified 194 patients matched on age, sex, race, and any comorbidity. In the sample with COVID-19 (N = 304), PLWH (9.1%) had lower rates of mortality than controls [19.1%; PM odds ratio (PM-OR): 0.41, 95% confidence interval (CI): 0.19-0.86]. Among hospitalized COVID-19 patients (N = 179), HIV infection was associated with lower rates of mechanical ventilation (PM-OR: 0.31, 95% CI: 0.11-0.84) and mortality (PM-OR: 0.40, 95% CI: 0. 17-0.95). In the extended pandemic period through April 2021, aggregate data by HIV status suggested elevated hospitalization and mortality rates in PLWH versus people without HIV. These results suggest that the direct biological impacts of the HIV virus do not negatively influence COVID-19-related outcomes when controlling for comorbidity and demographic variables.

Comorbidity and clinical factors associated with COVID-19 critical illness and mortality at a large public hospital in New York City in the early phase of the pandemic (March-April 2020)

BACKGROUND

Despite evidence of socio-demographic disparities in outcomes of COVID-19, little is known about characteristics and clinical outcomes of patients admitted to public hospitals during the COVID-19 outbreak.

OBJECTIVE

To assess demographics, comorbid conditions, and clinical factors associated with critical illness and mortality among patients diagnosed with COVID-19 at a public hospital in New York City (NYC) during the first month of the COVID-19 outbreak.

DESIGN

Retrospective chart review of patients diagnosed with COVID-19 admitted to NYC Health + Hospitals / Bellevue Hospital from March 9th to April 8th, 2020.

RESULTS

A total of 337 patients were diagnosed with COVID-19 during the study period. Primary analyses were conducted among those requiring supplemental oxygen (n = 270); half of these patients (135) were admitted to the intensive care unit (ICU). A majority were male (67.4%) and the median age was 58 years. Approximately one-third (32.6%) of hypoxic patients managed outside the ICU required non-rebreather or non-invasive ventilation. Requirement of renal replacement therapy occurred in 42.3% of ICU patients without baseline end-stage renal disease. Overall, 30-day mortality among hypoxic patients was 28.9% (53.3% in the ICU, 4.4% outside the ICU). In adjusted analyses, risk factors associated with mortality included dementia (adjusted risk ratio (aRR) 2.11 95%CI 1.50-2.96), age 65 or older (aRR 1.97, 95%CI 1.31-2.95), obesity (aRR 1.37, 95%CI 1.07-1.74), and male sex (aRR 1.32, 95%CI 1.04-1.70).

CONCLUSION

COVID-19 demonstrated severe morbidity and mortality in critically ill patients. Modifications in care delivery outside the ICU allowed the hospital to effectively care for a surge of critically ill and severely hypoxic patients.

2542. ID-Psych Addiction Rounds: A New Model to Address Opioid Use Disorder For Patients on the Infectious Disease Consult Service

Background

ID physicians often treat the infectious sequelae of opioid use disorder (OUD) and are uniquely poised to link hospitalized patients to substance use resources. In a large safety net hospital, we launched a multi-disciplinary initiative to ensure that patients on the ID consult service with OUD were always offered medication-assisted treatment (MAT). We used infections as “sentinel” events to identify patients with OUD and described the clinical characteristics of the high-risk patient population jointly consulted by ID and Psychiatry teams. This healthcare workforce initiative aimed to expand the role of ID providers in the opioid epidemic and decrease barriers to buprenorphine prescribing.

Methods

Every 2 weeks, ID fellows identified patients on their consult lists with infectious complications of OUD. Focused discussions were then held with the Psychiatry service and discussion of each patient continued at subsequent case conferences with attention paid to re-engaging those lost to follow-up. We performed chart abstraction of demographic and clinical characteristics as part of a quality improvement initiative.

Results

From October 2018 to March 2019, 23 patients were discussed at 10 case conferences with input from attendings, fellows, housestaff, social workers, and representatives from a novel Primary Care Safety Net program. The average patient age was 43 (range 24–50). Patients were predominantly male (65%), heroin users (90%) with high rates of HIV (22%) and untreated HCV (40%). ID-related infections included endocarditis (39%), osteomyelitis (31%), skin and soft-tissue infections (17%) and spinal abscesses (17%). The median time for a patient to be presented at an ID-Psych Addiction Rounds was 7 days (IQR 4.5–11.5). The mean length of hospitalization was 30 days (range 2–112). MAT was initiated in 75% of patients (41% buprenorphine; 59% methadone). The 30-day lost to follow-up rate was exceedingly high, with 80% of post-hospital appointments being missed.

Conclusion

ID physicians can effectively link hospitalized patients with OUD to substance use resources. A multi-disciplinary approach is key to addressing the opioid epidemic. Future work should explore how to create effective post-hospital transitions to decrease those lost to follow-up.

Disclosures

All authors: No reported disclosures.

High CIP2A levels correlate with an antiapoptotic phenotype that can be overcome by targeting BCL-XL in chronic myeloid leukemia

Cancerous inhibitor of protein phosphatase 2A (CIP2A) is a predictive biomarker of disease progression in many malignancies, including imatinib-treated chronic myeloid leukemia (CML). Although high CIP2A levels correlate with disease progression in CML, the underlying molecular mechanisms remain elusive. In a screen of diagnostic chronic phase samples from patients with high and low CIP2A protein levels, high CIP2A levels correlate with an antiapoptotic phenotype, characterized by downregulation of proapoptotic BCL-2 family members, including BIM, PUMA and HRK, and upregulation of the antiapoptotic protein BCL-XL. These results suggest that the poor prognosis of patients with high CIP2A levels is due to an antiapoptotic phenotype. Disrupting this antiapoptotic phenotype by inhibition of BCL-XL via RNA interference or A-1331852, a novel, potent and BCL-XL-selective inhibitor, resulted in extensive apoptosis either alone or in combination with imatinib, dasatinib or nilotinib, both in cell lines and in primary CD34(+) cells from patients with high levels of CIP2A. These results demonstrate that BCL-XL is the major antiapoptotic survival protein and may be a novel therapeutic target in CML.

The transrepression arm of glucocorticoid receptor signaling is protective in mutant huntingtin-mediated neurodegeneration

The unfolded protein response (UPR) occurs following the accumulation of unfolded proteins in the endoplasmic reticulum (ER) and orchestrates an intricate balance between its prosurvival and apoptotic arms to restore cellular homeostasis and integrity. However, in certain neurodegenerative diseases, the apoptotic arm of the UPR is enhanced, resulting in excessive neuronal cell death and disease progression, both of which can be overcome by modulating the UPR. Here, we describe a novel crosstalk between glucocorticoid receptor signaling and the apoptotic arm of the UPR, thus highlighting the potential of glucocorticoid therapy in treating neurodegenerative diseases. Several glucocorticoids, but not mineralocorticoids, selectively antagonize ER stress-induced apoptosis in a manner that is downstream of and/or independent of the conventional UPR pathways. Using GRT10, a novel selective pharmacological modulator of glucocorticoid signaling, we describe the importance of the transrepression arm of the glucocorticoid signaling pathway in protection against ER stress-induced apoptosis. Furthermore, we also observe the protective effects of glucocorticoids in vivo in a Drosophila model of Huntington's disease (HD), wherein treatment with different glucocorticoids diminished rhabdomere loss and conferred neuroprotection. Finally, we find that growth differentiation factor 15 has an important role downstream of glucocorticoid signaling in antagonizing ER stress-induced apoptosis in cells, as well as in preventing HD-mediated neurodegeneration in flies. Thus, our studies demonstrate that this novel crosstalk has the potential to be effectively exploited in alleviating several neurodegenerative disorders.

Diagnostic delays and clinical decision making with centralized Xpert MTB/RIF testing in Durban, South Africa

SETTING

We conducted a retrospective study among HIV-infected adult suspects (≥18 years) with pulmonary tuberculosis (TB), who underwent Xpert MTB/RIF (Xpert) testing at McCord Hospital and its adjoining HIV clinic in Durban, South Africa.

OBJECTIVE

To determine if Xpert testing performed at a centralized laboratory accelerated time to TB diagnosis.

DESIGN

We obtained data on sputum smear microscopy [acid-fast bacilli (AFB)], Xpert, and the rationale for treatment initiation from medical records. The primary outcome was "total diagnostic time," defined as time from sputum collection to clinicians' receipt of results. A linear mixed-effect model compared the duration of steps in the diagnostic pathway across testing modalities.

RESULTS

Among 403 participants, the median "total diagnostic time" for AFB and Xpert was 3.3 and 6.4 days, respectively (P < 0.001). When compared with AFB, the median delay for Xpert "laboratory processing" was 1.4 days (P < 0.001) and "result transfer to clinic" was 1.7 days (P < 0.001). Among 86 Xpert-positive participants who initiated treatment, 49 (57%) started treatment based on clinical suspicion or AFB-positive results, whereas only 32 (37%) started treatment based on Xpert-positive results.

CONCLUSIONS

In our setting, Xpert results took twice as long as AFB results to reach clinicians. Replacing AFB with centralized Xpert may delay TB diagnoses in some settings.

Role of Education in HIV Clinical Outcomes in a Tuberculosis Endemic Setting

This study evaluated how educational attainment impacts clinical outcomes of HIV-positive patients in Durban, South Africa. The authors conducted a prospective study of 466 adult HIV-positive patients initiating antiretroviral therapy (ART) at an urban TB-HIV clinic from October 2004 to June 2007. The level of educational attainment (highest grade completed) was assessed at ART initiation. The authors measured tuberculosis treatment outcomes as well as death, lost to follow-up, viral suppression (HIV RNA <400 copies/mL), and immunologic response (CD4 ≥200 cells/mm(3)) at 6, 12, and 24 months after ART initiation. After 24 months of ART initiation, there were 43 deaths; viral suppression and immunologic response were observed in 88% and 83% of the remaining patients, respectively. The authors found no association between level of educational attainment and mortality (P = .12), loss to follow-up (P = .85), virologic response (P = .51), or immunologic response (P = .63). Similar findings were observed at 6 and 12 months post-ART initiation.

Contraception and pregnancy in microbicide trials

The distinctive feature of the human immunodeficiency virus (HIV) epidemic in Sub-Saharan Africa is the burden on women, in particular young women of reproductive age. Consequently, most late-phase effectiveness microbicide clinical trials are conducted in sub-Saharan Africa where fertility rates are high. Because late-phase clinical trials are conducted over prolonged periods of time, women participating in these trials may fall pregnant during the trial. Their unborn babies may be exposed to a drug whose teratogenic potential is unknown if the investigational drug is not withdrawn. High pregnancy rates in such trials may compromise statistical integrity, as women will be withdrawn from the study drug for the duration of the pregnancy. It is therefore imperative for microbicide trials to implement effective contraceptive and pregnancy management programmes that maintain low pregnancy rates and the safety of unborn babies while not compromising the conduct and statistical integrity of the trial.

P73 and caspase-cleaved p73 fragments localize to mitochondria and augment TRAIL-induced apoptosis

The p73 protein, a member of the p53 family, has both developmental and tumorigenic functions. Here we show that p73 is cleaved by caspase-3 and -8 both in vitro and in vivo during apoptosis elicited by DNA-damaging drugs and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor ligation. TAp73 and some of its cleavage products are localized to mitochondria. siRNA-mediated downregulation of p73 expression induced a small but significant change in the susceptibility of HCT116 cells to TRAIL-induced apoptosis. A transcription-deficient mutant of TAp73 enhanced TRAIL-induced apoptosis suggesting that p73 protein has transcription-independent functions during death receptor-mediated apoptosis. Additionally, recombinant p73 protein induced cytochrome c release from isolated mitochondria providing evidence that nonnuclear p73 may have additional functions in the progression of apoptosis.

Downregulation of Mcl-1 potentiates HDACi-mediated apoptosis in leukemic cells

Mcl-1 is an antiapoptotic Bcl-2 family member, whose degradation is supposedly required for the induction of apoptosis. However, histone deacetylase inhibitors (HDACi) induce apoptosis primarily through the Bak/Mcl-1/Noxa and Bim pathways without decreasing Mcl-1. To investigate this discrepancy, we examined the role of Mcl-1 on HDACi-mediated apoptosis. Inhibition of either class I or class II HDAC by selective HDACi caused an upregulation of Mcl-1 mRNA and protein. Downregulation of Mcl-1 by three structurally unrelated cyclin-dependent kinase inhibitors potentiated HDACi-mediated apoptosis in primary chronic lymphocytic leukemic (CLL) cells and K562 cells. Sensitivity to HDACi-induced apoptosis was increased approximately 10-fold by the cyclin-dependent kinase inhibitors. Nanomolar concentrations of HDACi, approximately 300-fold lower than that required to induce apoptosis alone, sensitized cells to TRAIL, emphasizing that the mechanism(s) whereby HDACi induce apoptosis is clearly distinct from those by which they sensitize to TRAIL. Furthermore, knockdown of Mcl-1-potentiated HDACi-mediated apoptosis in K562 cells. Thus, HDACi-mediated Mcl-1 upregulation plays an important antiapoptotic regulatory role in limiting the efficacy of HDACi-induced apoptosis, which can be overcome by combination with an agent that downregulates Mcl-1. Thus, a clinical trial in some cancers is warranted using a combination of an HDACi with agents that downregulate Mcl-1.

Apoptosis induced by histone deacetylase inhibitors in leukemic cells is mediated by Bim and Noxa

Several histone deacetylase inhibitors (HDACi), which have recently entered early clinical trials, exert their anticancer activity in part through the induction of apoptosis although the precise mechanism of this induction is not known. Induction of apoptosis by structurally diverse HDACi in primary cells from patients with chronic lymphocytic leukemia (CLL) and different leukemic cell lines was mediated by the Bcl-2 regulated intrinsic pathway and demonstrated a requirement for de novo protein synthesis. A marked time-dependent induction of the pro-apoptotic BH3-only proteins, Bim, Noxa and Bmf was observed, which preceded the induction of apoptosis. A key role for both Bim and Noxa was proposed in HDACi-mediated apoptosis based on our findings that siRNA for Bim and Noxa but not Bmf largely prevented the HDACi-induced loss in mitochondrial membrane potential, caspase processing and phosphatidylserine externalization. Noxa, induced by HDACi, in CLL cells and tumor cell lines, bound extensively to Mcl-1, a major anti-apoptotic Bcl-2 family member present in CLL cells. Our data strongly suggests that HDACi induce apoptosis primarily through inactivation of anti-apoptotic Bcl-2 family members by increases in Bim and Noxa and highlights these increases as a potential clinical target for CLL/lymphoma therapy.

Downregulation of Bcr-Abl in K562 cells restores susceptibility to apoptosis: characterization of the apoptotic death

We examined the susceptibility of a variety of human leukemic cell lines to the induction of apoptosis. K562, a chronic myelogenous leukemic cell line which expresses the bcr-abl fusion gene, was found to be extremely resistant to apoptosis, irrespective of the inducing agent. This resistance can be attributed to the deregulated Abl kinase activity of bcr-abl, as downregulation of its expression using antisense oligodeoxynucleotides targeted to the beginning of the abl sequence in this chimeric gene rendered these cells susceptible to cytotoxic drug-induced apoptosis. Examination of the morphological and biochemical features of apoptosis in K562 cells revealed the typical membrane blebbing and chromatin condensation associated with this form of cell death. In situ TdT-mediated end labeling of the DNA revealed the presence of strand breaks in the treated cells and field inversion gel electrophoresis revealed the presence of large 10-50 kb fragments. However there was an absence of oligonucleosomal DNA fragmentation, whether or not Bcr-Abl was expressed. Thus, while inhibition of expression of Bcr-Abl renders K562 cells susceptible to apoptosis, the absence of oligonucleosomal DNA fragmentation in these cells is independent of the function of this molecule.

Histone deacetylase inhibitors potentiate TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis in lymphoid malignancies

New therapies are required for chronic lymphocytic leukemia (CLL), an incurable disease characterized by failure of mature lymphocytes to undergo apoptosis. Activation of cell surface death receptors, such as via TRAIL receptor ligation, may provide a novel therapeutic target for various malignancies. However, CLL and other lymphoid malignancies are resistant to TRAIL. We report that low concentrations of histone deacetylase (HDAC) inhibitors, such as depsipeptide, which alone failed to induce apoptosis, markedly sensitize CLL cells and other primary lymphoid malignancies to TRAIL-induced apoptosis. These combinations caused little or no toxicity to normal lymphocytes. HDAC inhibitors sensitized resistant cells to TRAIL-induced apoptosis by facilitating formation of an active death-inducing signalling complex (DISC), leading to the rapid activation of caspase-8. The facilitated DISC formation also occurred in the absence of TRAIL-R2 upregulation. Thus, the combination of HDAC inhibitors and TRAIL may be valuable in the treatment of various hemopoietic malignancies.

Chronic lymphocytic leukemic cells exhibit apoptotic signaling via TRAIL-R1

Clinical trials have been initiated with Apo2L/TRAIL (Genentech) and agonistic mAbs to TRAIL receptors, -R1 and -R2 (Human Genome Sciences). The apoptosis-inducing ability of these mAbs and different TRAIL preparations, in the presence or absence of histone deacetylase inhibitors (HDACi), varied markedly against primary chronic lymphocytic leukaemia (CLL) cells and various tumor cell lines, demonstrating an unanticipated preferential apoptotic signaling via either TRAIL-R1 or -R2. Contrary to literature reports that TRAIL-induced apoptosis occurs primarily via signaling through TRAIL-R2, CLL cells, in the presence of HDACi, undergo predominantly TRAIL-R1-mediated apoptosis. Consequently, Apo2L/TRAIL, which signals primarily through TRAIL-R2, is virtually devoid of activity against CLL cells. To maximize therapeutic benefit, it is essential to ascertain whether a primary tumor signals via TRAIL-R1/-R2, prior to initiating therapy. Thus combination of an agonistic TRAIL-R1 Ab and an HDACi, such as the anticonvulsant sodium valproate, could be of value in treating CLL.

Increased sensitivity to TRAIL-induced apoptosis occurs during the adenoma to carcinoma transition of colorectal carcinogenesis

The death ligand TRAIL (Apo2L) has potential for cancer therapy, since tumour cells are thought to be more sensitive than normal cells. We investigated whether sensitivity to TRAIL increases during the adenoma to carcinoma transition of colorectal carcinogenesis. Under the same culture conditions, we compared the extent of TRAIL-induced apoptosis in four premalignant adenoma and three carcinoma cell lines. Although TRAIL induced some apoptosis in adenoma cultures, the carcinoma cell lines were significantly more sensitive (P<0.001). This finding was recapitulated in an in vitro model of tumour progression in which conversion of the adenoma cell line AA/C1 to a tumorigenic phenotype was associated with increased TRAIL sensitivity (P<0.001). Increased TRAIL sensitivity during colorectal carcinogenesis has been previously attributed to changes in the balance between TRAIL receptors TRAIL-R1 and -R2 and ‘decoy’ receptors TRAIL-R3 and -R4 during malignant progression. To address this, cell surface receptor expression was measured by flow cytometry. In summary, during colorectal carcinogenesis, there is a marked increase in sensitivity to TRAIL-induced apoptosis associated with progression from benign to malignant tumour that could be exploited for colon cancer therapy, but alterations in cell surface TRAIL receptor expression may not be the primary reason for this change.

CDDO induces apoptosis via the intrinsic pathway in lymphoid cells

The peroxisome-proliferator-activated receptor (PPAR) gamma agonist, CDDO, is under investigation for use in various malignancies. The mechanisms by which CDDO induces apoptosis are controversial. We have therefore sought to determine these mechanisms using primary chronic lymphocyte leukemic (CLL) cells and Jurkat cell lines with defined apoptotic abnormalities. In these cells, CDDO induced-apoptosis involved caspase-independent loss in mitochondrial membrane potential followed by caspase processing. The pattern of CDDO-induced caspase processing, defined by use of a caspase inhibitor, strongly suggested that caspase-9 was the apical caspase. Moreover, CDDO induced apoptosis in caspase-8 and FADD-deficient but not in Bcl-xL overexpressing Jurkat cells. In CLL cells, CDDO induced an early release of mitochondrial cytochrome c and Smac that preceded apoptosis. Thus, in both cell types, CDDO induced apoptosis primarily by the intrinsic pathway with caspase-9 as the apical caspase. This has important implications in the design of novel agents for the treatment of CLL and other malignancies.

Apoptosis in human monocytic THP.1 cells involves several distinct targets of N-tosyl-L-phenylalanyl chloromethyl ketone (TPCK)

N-Tosyl-L-phenylalanyl chloromethyl ketone (TPCK), a chymotrypsin-like serine protease inhibitor, affected apoptosis in human monocytic THP.1 cells differently dependent on both the concentration used and the apoptotic stimulus. TPCK (50 - 75 microM) induced both biochemical and ultrastructural changes characteristic of apoptosis, including proteolysis of poly (ADP-ribose) polymerase (PARP) and lamins together with formation of large kilobase pair fragments of DNA, particularly of 30 - 50 and 200 - 300 kilobase pairs in length but without internucleosomal cleavage of DNA. The induction of apoptosis by TPCK also involved the processing of CPP32 and Mch 3 to their catalytically active subunits. Benzyloxycarbonyl-Val-Ala-Asp (OMe) fluoromethyl ketone (Z-VAD.FMK), an ICE-like protease inhibitor, completely prevented all the biochemical and morphological changes induced by TPCK demonstrating the involvement of ICE-like proteases in the execution phase of apoptosis. Lower concentrations of TPCK (5 - 20 microM) prevented internucleosomal cleavage of DNA induced by other apoptotic stimuli. TPCK (10 microM) inhibited cell death induced by etoposide but potentiated that induced by cycloheximide demonstrating that it differentially affected apoptosis in THP.1 cells dependent on the stimulus used. These results are consistent with at least three distinct TPCK targets, one being important for cell survival, the second in facilitating internucleosomal cleavage of DNA and the third in the modulation of apoptosis induced by different apoptotic stimuli.

Bisindolylmaleimide IX is a potent inducer of apoptosis in chronic lymphocytic leukaemic cells and activates cleavage of Mcl-1

New agents are required for the treatment of chronic lymphocytic leukaemia (CLL). We show here that a protein kinase C inhibitor, bisindolylmaleimide IX, is a potent inducer of apoptosis in CLL cells, and investigate the mechanisms by which this is induced. Bisindolylmaleimide IX induced a conformational change and subcellular redistribution of Bax from the cytosol to the mitochondria, resulting in the release of the proapoptotic mediators cytochrome c, Smac and Omi/HtrA2 from the mitochondrial inner membrane space. This was followed by the activation of caspase-9 as the apical caspase and subsequent activation of effector caspases. CLL cells undergoing apoptosis showed a rapid caspase-mediated cleavage of Mcl-1, an antiapoptotic member of the Bcl-2 family implicated in CLL survival and poor prognosis. This cleavage was mediated primarily by caspase-3. Cleavage of Mcl-1 may provide a feed-forward amplification loop, resulting in the rapid induction of apoptosis. Bisindolylmaleimide IX or a related derivative may be of clinical use in the treatment of CLL.

Macrophage-mediated clearance of cells undergoing caspase-3-independent death

Little is known of the functions of caspases in mediating the surface changes required for phagocytosis of dying cells. Here we investigate the role played by the effector caspase, caspase-3 in this process using the caspase-3-defective MCF-7 breast carcinoma line and derived caspase-3-expressing transfectants. Our results indicate that, while certain typical features of apoptosis induced by etoposide--namely classical morphological changes and the ability to degrade DNA into oligonucleosomal fragments - are caspase-3-dependent, loss of cell adhesion to plastic and the capacity to interact with, and to be phagocytosed by, human monocyte-derived macrophages - both by CD14-dependent and CD14-independent mechanisms--do not require caspase-3. Furthermore, both etoposide-induced caspase-3-positive and -negative MCF-7 cells suppressed proinflammatory cytokine release by macrophages. These results demonstrate directly that cell surface changes that are sufficient for anti-inflammatory clearance by human macrophages can be regulated independently of stereotypical features of the apoptosis programme that require caspase-3.

XIAP inhibition of caspase-3 preserves its association with the Apaf-1 apoptosome and prevents CD95- and Bax-induced apoptosis

Ligation of death receptors or formation of the Apaf-1 apoptosome results in the activation of caspases and execution of apoptosis. We recently demonstrated that X-linked inhibitor-of-apoptosis protein (XIAP) associates with the apoptosome in vitro. By utilizing XIAP mutants, we now report that XIAP binds to the 'native' apoptosome complex via a specific interaction with the small p12 subunit of processed caspase-9. Indeed, we provide the first direct evidence that XIAP can simultaneously bind active caspases-9 and -3 within the same complex and that inhibition of caspase-3 by the Linker-BIR2 domain prevents disruption of BIR3-caspase-9 interactions. Recent studies suggest that inhibition of caspase-3 is dispensable for its anti-apoptotic effects. However, we clearly demonstrate that inhibition of caspase-3 is required to inhibit CD95 (Fas/Apo-1)-mediated apoptosis, whereas inhibition of either caspase-9 or caspase-3 prevents Bax-induced cell death. Finally, we illustrate for the first time that XIAP mutants, which are incapable of binding to caspases-9 and -3 are completely devoid of anti-apoptotic activity. Thus, XIAP's capacity to maintain inhibition of caspase-9 within the Apaf-1 apoptosome is influenced by its ability to simultaneously inhibit active caspase-3, and depending upon the apoptotic stimulus, inhibition of caspase-9 or 3 is essential for XIAP's anti-apoptotic activity.

The proteasome: a novel target for cancer chemotherapy

The ubiquitin-proteasome system is an important regulator of cell growth and apoptosis. The potential of specific proteasome inhibitors to act as novel anti-cancer agents is currently under intensive investigation. Several proteasome inhibitors exert anti-tumour activity in vivo and potently induce apoptosis in tumour cells in vitro, including those resistant to conventional chemotherapeutic agents. By inhibiting NF-kappaB transcriptional activity, proteasome inhibitors may also prevent angiogenesis and metastasis in vivo and further increase the sensitivity of cancer cells to apoptosis. Proteasome inhibitors also exhibit some level of selective cytotoxicity to cancer cells by preferentially inducing apoptosis in proliferating or transformed cells or by overcoming deficiencies in growth-inhibitory or pro-apoptotic molecules. High expression of oncogene products like c-Myc also makes cancer cells more susceptible to proteasome inhibitor-induced apoptosis. The induction of apoptosis by proteasome inhibitors varies between cell types but often occurs following an initial accumulation of short-lived proteins such as p53, p27, pro-apoptotic Bcl-2 family members or activation of the stress kinase JNK. These initial events often result in a perturbation of mitochondria with concomitant release of cytochrome c and activation of the Apaf-1 containing apoptosome complex. This results in activation of the apical caspase-9 followed by activation of effector caspases-3 and -7, which are responsible for the biochemical and morphological changes associated with apoptosis.

Physiological concentrations of K+ inhibit cytochrome c-dependent formation of the apoptosome

In many forms of apoptosis, cytochrome c released from mitochondria induces the oligomerization of Apaf-1 to form a caspase-activating apoptosome complex. Activation of lysates in vitro with dATP and cytochrome c results in the formation of an active caspase-processing approximately 700-kDa apoptosome complex, which predominates in apoptotic cells, and a relatively inactive approximately 1.4-MDa complex. We now demonstrate that assembly of the active complex is suppressed by normal intracellular concentrations of K(+). Using a defined apoptosome reconstitution system with recombinant Apaf-1 and cytochrome c, K(+) also inhibits caspase activation by abrogating Apaf-1 oligomerization and apoptosome assembly. Once assembled, the apoptosome is relatively insensitive to the effects of ionic strength and processes/activates effector caspases. The inhibitory effects of K(+) on apoptosome formation are antagonized in a concentration-dependent manner by cytochrome c. These studies support the hypothesis that the normal intracellular concentrations of K(+) act to safeguard the cell against inappropriate formation of the apoptosome complex, caused by the inadvertent release of small amounts of cytochrome c. Thus, the assembly and activation of the apoptosome complex in the cell requires the rapid and extensive release of cytochrome c to overcome the inhibitory effects of normal intracellular concentrations of K(+).

Interleukin-5 inhibits translocation of Bax to the mitochondria, cytochrome c release, and activation of caspases in human eosinophils

The apoptosis and subsequent clearance of eosinophils without histotoxic mediator release is thought to be crucial in the resolution of airway inflammation in asthma. Interleukin-5 (IL-5) is a potent suppressor of eosinophil apoptosis. The mechanism by which IL-5 inhibits spontaneous eosinophil apoptosis was investigated. Freshly isolated eosinophils constitutively expressed the conformationally active form of Bax in the cytosol and nucleus. During spontaneous and staurosporine-induced apoptosis, Bax underwent a caspase-independent translocation to the mitochondria, which was inhibited by IL-5. Eosinophil apoptosis was associated with the release of cytochrome c from the mitochondria, which was also inhibited by IL-5. IL-5 and the cell-permeable caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-(OMe) fluoromethyl ketone (z-VAD.fmk), prevented phosphatidylserine (PS) externalization, although only IL-5 inhibited loss of mitochondrial membrane potential (DeltaPsim). Peripheral blood eosinophils endogenously expressed "initiator" caspase-8 and -9, and "effector" caspase-3, -6, and -7. Spontaneous eosinophil apoptosis was associated with processing of caspase-3, -6, -7, -8, and -9. IL-5 and z-VAD.fmk prevented caspase activation in spontaneous apoptosis. The results suggest that spontaneous eosinophil apoptosis involves Bax translocation to the mitochondria, cytochrome c release, caspase-independent perturbation of the mitochondrial membrane, and subsequent activation of caspases. IL-5 inhibits spontaneous eosinophil apoptosis at a site upstream of Bax translocation.

Modulation of tumor necrosis factor apoptosis-inducing ligand- induced NF-kappa B activation by inhibition of apical caspases

Tumor necrosis factor (TNF) apoptosis-inducing ligand (TRAIL), a member of the TNF family, induces apoptosis in many transformed cells. We report TRAIL-induced NF-kappaB activation, concomitant with production of the pro-inflammatory cytokine Interleukin-8 in the relatively TRAIL-insensitive cell line, HEK293. In contrast, TRAIL-induced NF-kappaB activation occurred in HeLa cells only upon pretreatment with the caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-(OMe) fluoromethyl ketone (z-VAD.fmk), indicating that this was due to a caspase-sensitive component of TRAIL-induced NF-kappaB activation. NF-kappaB activation was mediated by the death receptors, TRAIL-R1 and -R2, but not by TRAIL-R3 or -R4 and was only observed in HeLa cells in the presence of z-VAD.fmk. Receptor-interacting protein, an obligatory component of TNF-alpha-induced NF-kappaB activation, was cleaved during TRAIL-induced apoptosis. We show that receptor-interacting protein is recruited to the native TRAIL death-inducing signaling complex (DISC) and that recruitment is enhanced in the presence of z-VAD.fmk, thus providing an explanation for the potentiation of TRAIL-induced NF-kappaB activation by z-VAD.fmk in TRAIL-sensitive cell lines. Examination of the TRAIL DISC in sensitive and resistant cells suggests that a high ratio of c-FLIP to caspase-8 may partially explain cellular resistance to TRAIL-induced apoptosis. Sensitivity to TRAIL-induced apoptosis was also modulated by inhibition or activation of NF-kappaB. Thus, in some contexts, modulation of NF-kappaB activation possibly at the level of apical caspase activation at the DISC may be a key determinant of sensitivity to TRAIL-induced apoptosis.

Proteasome inhibitor-induced apoptosis of B-chronic lymphocytic leukaemia cells involves cytochrome c release and caspase activation, accompanied by formation of an approximately 700 kDa Apaf-1 containing apoptosome complex

Proteasome inhibitors, including lactacystin and MG132 (carbobenzoxyl-leucinyl-leucinyl-leucinal), potently induce apoptosis in leukaemic B cells from patients with B cell chronic lymphocytic leukaemia (B-CLL). This pro-apoptotic effect occurs in cells from patients at all stages of the disease, including those resistant to conventional chemotherapy, suggesting that proteasome inhibitors may be useful for treatment of B-CLL. Following initial inhibition of proteasomal activity, these agents induce mitochondrial cytochrome c release and caspase-dependent apoptosis, involving cleavage/activation of caspases -2, -3, -7, -8 and -9. Pre-treatment with the cell permeable caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp (OMe)fluoromethyl ketone (Z-VAD.fmk), did not prevent the release of cytochrome c or partial processing of caspase-9 but prevented activation of effector caspases and the induction of apoptosis. These results suggest that the release of cytochrome c is caspase independent and that caspase-9 is the initiator caspase in proteasome inhibitor-induced apoptosis of B-CLL cells. Activation of B-CLL lysates with dATP results in the formation of an approximately 700 kDa caspase-activating apoptosome complex containing Apaf-1. We describe for the first time the formation of a similar approximately 700 kDa caspase-activating apoptosome complex in B-CLL cells induced to undergo apoptosis by proteasome inhibitors.

Elevated extracellular [K+] inhibits death-receptor- and chemical-mediated apoptosis prior to caspase activation and cytochrome c release

Efflux of intracellular K(+) and cell shrinkage are features of apoptosis in many experimental systems, and a regulatory role has been proposed for cytoplasmic [K(+)] in initiating apoptosis. We have investigated this in both death-receptor-mediated and chemical-induced apoptosis. Using Jurkat T cells pre-loaded with the K(+) ion surrogate (86)Rb(+), we have demonstrated an efflux of intracellular K(+) during apoptosis that was concomitant with, but did not precede, other apoptotic changes, including phosphatidylserine externalization, mitochondrial depolarization and cell shrinkage. To further clarify the role of K(+) ions in apoptosis, cytoprotection by elevated extracellular [K(+)] was studied. Induction of apoptosis by diverse death-receptor and chemical stimuli in two cell lines was inhibited prior to phosphatidylserine externalization, mitochondrial depolarization, cytochrome c release and caspase activation. Using a cell-free system, we have demonstrated a novel mechanism by which increasing [K(+)] inhibited caspase activation. In control dATP-activated lysates, Apaf-1 oligomerized to a biologically active caspase processing approximately 700 kDa complex and an inactive approximately 1.4 MDa complex. Increasing [K(+)] inhibited caspase activation by preventing formation of the approximately 700 kDa complex, but not of the inactive complex. Thus intracellular and extracellular [K(+)] markedly affect caspase activation and the initiation of apoptosis induced by both death-receptor ligation and chemical stress.

Apoptotic death sensor: an organelle's alter ego?

Caspases are intracellular cysteine proteases that are primarily responsible for the stereotypic morphological and biochemical changes that are associated with apoptosis. Caspases are often activated by the apoptotic protease-activating factor 1 (APAF-1) apoptosome, a complex that is formed following mitochondrial release of cytochrome c in response to many death-inducing stimuli. Both pro- and anti-apoptotic BCL-2 family members regulate apoptosis, primarily by their effects on mitochondria, whereas many inhibitor of apoptosis proteins (IAPs) regulate apoptosis by directly inhibiting distinct caspases. Exposure of cells to chemicals and radiation, as well as loss of trophic stimuli, perturb cellular homeostasis and, depending on the type of cellular stress, particular or multiple organelles appear to 'sense' the damage and signal the cell to undergo apoptosis by stimulating the formation of unique and/or common caspase-activating complexes.

"Have you seen this?" Diffuse hepatic apoptosis

One important cell death pathway involves binding of the cell surface receptor Fas, which recruits and activates specific initiator and effector caspases. In this study Balb/c mice were injected with monoclonal antibody to Fas either alone or followed by the tripeptide caspase inhibitor Z-VAD.fmk. At four hours mice were killed along with concurrent controls and tissues processed for histological examination and immunocytochemical staining for cleaved caspase-3. The livers in all animals treated with Fas alone showed massive apoptosis and positive staining for cleaved caspase-3 whereas those treated with Fas and Z-VAD.fmk or controls showed little or no apoptosis or staining for cleaved caspase-3. These features suggest that massive apoptosis may be important in fulminant liver disease.

Caspase-3 cleaves Apaf-1 into an approximately 30 kDa fragment that associates with an inappropriately oligomerized and biologically inactive approximately 1.4 MDa apoptosome complex

Cytochrome c and dATP/ATP induce oligomerization of Apaf-1 into two distinct apoptosome complexes: an approximately 700 kDa complex, which recruits and activates caspases-9, -3 and -7, and an approximately 1.4 MDa complex, which recruits and processes caspase-9, but does not efficiently activate effector caspases. While searching for potential inhibitors of the approximately 1.4 MDa apoptosome complex, we observed an approximately 30 kDa Apaf-1 immunoreactive fragment that was associated exclusively with the inactive complex. We subsequently determined that caspase-3 cleaved Apaf-1 within its CED-4 domain (SVTD(271) downward arrowS) in both dATP-activated lysates and apoptotic cells to form a prominent approximately 30 kDa (p30) N-terminal fragment. Purified recombinant Apaf-1 p30 fragment weakly inhibited dATP-dependent activation of caspase-3 in vitro. However, more importantly, prevention of endogenous formation of the p30 fragment did not stimulate latent effector caspase processing activity in the large complex. Similarly, the possibility that XIAP, an inhibitor of apoptosis protein (IAP), was responsible for the inactivity of the approximately 1.4 MDa complex was excluded as immunodepletion of this caspase inhibitor failed to relieve the inhibition. However, selective proteolytic digestion of the approximately 1.4 MDa and approximately 700 kDa complexes showed that Apaf-1 was present in conformationally distinct forms in these two complexes. Therefore, the inability of the approximately 1.4 MDa apoptosome complex to process effector caspases most likely results from inappropriately folded or oligomerized Apaf-1.

Economic impact of influenza vaccination in preschool children

OBJECTIVE

The economic impact of routine vaccination of preschool children with inactivated influenza vaccine was investigated.

DESIGN

A decision analysis was performed using data from the literature. Direct and indirect costs of each vaccination strategy were calculated and compared with a strategy of not vaccinating.

SETTING

Two settings were evaluated: a setting in which vaccination was available during flexible hours and a setting in which vaccination was available only during usual work hours (8:00 am-5:00 pm).

RESULTS

Vaccination resulted in a net cost savings in both settings. The net savings per vaccine recipient were $21.28 in the flexible setting and $1.20 in the restricted setting. Although the analysis was performed for the inactivated vaccine, sensitivity analysis showed that the nasal vaccine could also result in a net cost savings depending on the price of the cold-adapted vaccine when it is licensed.

CONCLUSION

Vaccinating preschool children is economically advantageous. Serious consideration should be given to recommending vaccination in this age group.

Heat-shock protein 70 inhibits apoptosis by preventing recruitment of procaspase-9 to the Apaf-1 apoptosome

The cellular-stress response can mediate cellular protection through expression of heat-shock protein (Hsp) 70, which can interfere with the process of apoptotic cell death. Stress-induced apoptosis proceeds through a defined biochemical process that involves cytochrome c, Apaf-1 and caspase proteases. Here we show, using a cell-free system, that Hsp70 prevents cytochrome c/dATP-mediated caspase activation, but allows the formation of Apaf-1 oligomers. Hsp70 binds to Apaf-1 but not to procaspase-9, and prevents recruitment of caspases to the apoptosome complex. Hsp70 therefore suppresses apoptosis by directly associating with Apaf-1 and blocking the assembly of a functional apoptosome.

A reappraisal of the role of Zn2+ in TGF-beta1-induced apoptosis in primary hepatocytes

There is now a wealth of information regarding the apoptotic mode of cell death and its importance in toxicological studies in many mammalian organs including the liver. In this study, we investigated the modulatory effects of the heavy metal Zn2+ on transforming growth factor-beta1 (TGF-beta1)-induced apoptosis in primary rat hepatocytes. Apoptosis induced by TGF-beta1 (1 ng/ml) in hepatocytes was accompanied by nuclear condensation as assessed morphologically by staining with Hoechst 33258 and DNA cleavage as detected biochemically by in situ end-labeling, field inversion and conventional gel electrophoresis. Pretreatment with 100 micromol/L Zn2+ abrogated the nuclear condensation, in situ end-labeling, and DNA laddering in TGF-beta1-treated hepatocytes. Surprisingly, Zn2+ did not inhibit the formation of high-molecular-weight DNA fragments (30-50 kbp to 250-300 kbp). These data provide evidence that Zn2+ exerts its effects on the endonucleases that act downstream in the execution phase of TGF-beta1-induced apoptosis in hepatocytes.

JNK (c-Jun N-terminal kinase) and p38 activation in receptor-mediated and chemically-induced apoptosis of T-cells: differential requirements for caspase activation

Activation of the stress-activated mitogen-activated protein kinases (MAP kinases), c-Jun N-terminal kinase (JNK) and p38, is necessary for the induction of apoptosis in neuronal cells; however, in other cell types their involvement may be stimulus-dependent. In the present study we investigate the activation of JNK and p38 in a single non-neuronal cell type, undergoing receptor-mediated (tumour necrosis factor-related apoptosis-inducing ligand and CD95) or chemically-induced (lactacystin) apoptosis. In Jurkat T-cells, receptor-mediated and chemically-induced apoptosis resulted in a time-dependent activation of the initiator caspases-8 and -9, respectively. Both types of stimuli resulted in a significant activation of JNK and p38, which closely paralleled the time-dependent induction of apoptosis. The caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-(OMe) fluoromethyl ketone (z-VAD.FMK) inhibited receptor-mediated apoptosis and suppressed JNK and p38 activation. In contrast, inhibition of lactacystin-induced apoptosis with z-VAD.FMK, as assessed by phosphatidylserine exposure and poly(ADP-ribose) polymerase cleavage, did not inhibit activation of JNK or p38, demonstrating that during chemically-induced apoptosis, activation of JNK and p38 is independent of effector caspases. The role of p38 in apoptosis was assessed using the specific p38 inhibitor, SB203580. No effect on the induction of apoptosis or caspase activation was observed, although activation of mitogen-activated protein kinase-activated protein kinase-2 (MAPKAPK-2), an immediate downstream target of p38, was inhibited. Therefore neither p38 activation nor activation of MAPKAPK-2 is critical for induction of either receptor- or chemically-induced apoptosis. Thus, within a single cell type, (1) the mechanism of p38 and JNK activation during apoptosis is stimulus-dependent and (2) activation of the p38 pathway is not required for caspase activation or apoptosis, assessed by phosphatidylserine exposure, but may still be required to elicit other features of the apoptotic phenotype.

Protein complexes activate distinct caspase cascades in death receptor and stress-induced apoptosis

Caspases play a central role in the execution phase of apoptosis and are responsible for many of the morphological features normally associated with this form of cell death. Caspases can activate one another and consequently can initiate specific caspase cascades. Caspases-8 and -9 appear to be the apical caspases activated in death receptor- and mitochondrial stress-induced apoptosis, respectively. The role of large protein complexes in mediating these pathways is discussed.

Apaf-1 oligomerizes into biologically active approximately 700-kDa and inactive approximately 1.4-MDa apoptosome complexes

Apaf-1, by binding to and activating caspase-9, plays a critical role in apoptosis. Oligomerization of Apaf-1, in the presence of dATP and cytochrome c, is required for the activation of caspase-9 and produces a caspase activating apoptosome complex. Reconstitution studies with recombinant proteins have indicated that the size of this complex is very large in the order of approximately 1.4 MDa. We now demonstrate that dATP activation of cell lysates results in the formation of two large Apaf-1-containing apoptosome complexes with M(r) values of approximately 1.4 MDa and approximately 700 kDa. Kinetic analysis demonstrates that in vitro the approximately 700-kDa complex is produced more rapidly than the approximately 1.4 MDa complex and exhibits a much greater ability to activate effector caspases. Significantly, in human tumor monocytic cells undergoing apoptosis after treatment with either etoposide or N-tosyl-l-phenylalanyl chloromethyl ketone (TPCK), the approximately 700-kDa Apaf-1 containing apoptosome complex was predominately formed. This complex processed effector caspases. Thus, the approximately 700-kDa complex appears to be the correctly formed and biologically active apoptosome complex, which is assembled during apoptosis.

Distinguished Scientists Lecture Series. HIV-associated nephropathy

HIV-associated nephropathy is manifested by heavy proteinuria and renal insufficiency and characterized pathologically by the collapsing variant of focal and segmental glomerulosclerosis with acute tubular necrosis and mild interstitial inflammation. Untreated, it may result in end-stage renal disease in as little as 4 months. It may present in patients with any manifestation of HIV infection, and affects predominantly black individuals. Insights into pathogenesis have come from a transgenic mouse model, renal cell cultures, and from study of human biopsy material. Although the pathogenesis is not completely understood, current considerations revolve around the role of HIV or protein in renal epithelium and the effects of cytokines, including transforming growth factor-beta and basic fibroblast growth factor, on renal structures. Therapy with zidovudine, corticosteroids, or angiotensin-converting enzyme inhibitors has met with modest success; to date, protease inhibitors have not been assessed.

Caspase activation involves the formation of the aposome, a large (approximately 700 kDa) caspase-activating complex

In mammals, apoptotic protease-activating factor 1 (Apaf-1), cytochrome c, and dATP activate caspase-9, which initiates the postmitochondrial-mediated caspase cascade by proteolytic cleavage/activation of effector caspases to form active approximately 60-kDa heterotetramers. We now demonstrate that activation of caspases either in apoptotic cells or following dATP activation of cell lysates results in the formation of two large but different sized protein complexes, the "aposome" and the "microaposome". Surprisingly, most of the DEVDase activity in the lysate was present in the aposome and microaposome complexes with only small amounts of active caspase-3 present as its free approximately 60-kDa heterotetramer. The larger aposome complex (M(r) = approximately 700,000) contained Apaf-1 and processed caspase-9, -3, and -7. The smaller microaposome complex (M(r) = approximately 200,000-300,000) contained active caspase-3 and -7 but little if any Apaf-1 or active caspase-9. Lysates isolated from control THP.1 cells, prior to caspase activation, showed striking differences in the distribution of key apoptotic proteins. Apaf-1 and procaspase-7 may be functionally complexed as they eluted as an approximately 200-300-kDa complex, which did not have caspase cleavage (DEVDase) activity. Procaspase-3 and -9 were present as separate and smaller 60-90-kDa (dimer) complexes. During caspase activation, Apaf-1, caspase-9, and the effector caspases redistributed and formed the aposome. This resulted in the processing of the effector caspases, which were then released, possibly bound to other proteins, to form the microaposome complex.