Do health education initiatives assist socioeconomically disadvantaged populations? A systematic review and meta-analyses.

BACKGROUND: Health education interventions are considered critical for the prevention and management of conditions of public health concern. Although the burden of these conditions is often greatest in socio-economically disadvantaged populations, the effectiveness of interventions that target these groups is unknown. We aimed to identify and synthesize evidence of the effectiveness of health-related educational interventions in adult disadvantaged populations. METHODS: We pre-registered the study on Open Science Framework https://osf.io/ek5yg/ . We searched Medline, Embase, Emcare, and the Cochrane Register from inception to 5/04/2022 to identify studies evaluating the effectiveness of health-related educational interventions delivered to adults in socio-economically disadvantaged populations. Our primary outcome was health related behaviour and our secondary outcome was a relevant biomarker. Two reviewers screened studies, extracted data and evaluated risk of bias. Our synthesis strategy involved random-effects meta-analyses and vote-counting. RESULTS: We identified 8618 unique records, 96 met our criteria for inclusion - involving more than 57,000 participants from 22 countries. All studies had high or unclear risk of bias. For our primary outcome of behaviour, meta-analyses found a standardised mean effect of education on physical activity of 0.05 (95% confidence interval (CI) = -0.09-0.19), (5 studies, n = 1330) and on cancer screening of 0.29 (95% CI = 0.05-0.52), (5 studies, n = 2388). Considerable statistical heterogeneity was present. Sixty-seven of 81 studies with behavioural outcomes had point estimates favouring the intervention (83% (95% CI = 73%-90%), p < 0.001); 21 of 28 studies with biomarker outcomes showed benefit (75% (95%CI = 56%-88%), p = 0.002). When effectiveness was determined based on conclusions in the included studies, 47% of interventions were effective on behavioural outcomes, and 27% on biomarkers. CONCLUSIONS: Evidence does not demonstrate consistent, positive impacts of educational interventions on health behaviours or biomarkers in socio-economically disadvantaged populations. Continued investment in targeted approaches, coinciding with development of greater understanding of factors determining successful implementation and evaluation, are important to reduce inequalities in health.

Prdm6 is essential for cardiovascular development in vivo.

Members of the PRDM protein family have been shown to play important roles during embryonic development. Previous in vitro and in situ analyses indicated a function of Prdm6 in cells of the vascular system. To reveal physiological functions of Prdm6, we generated conditional Prdm6-deficient mice. Complete deletion of Prdm6 results in embryonic lethality due to cardiovascular defects associated with aberrations in vascular patterning. However, smooth muscle cells could be regularly differentiated from Prdm6-deficient embryonic stem cells and vascular smooth muscle cells were present and proliferated normally in Prdm6-deficient embryos. Conditional deletion of Prdm6 in the smooth muscle cell lineage using a SM22-Cre driver line resulted in perinatal lethality due to hemorrhage in the lungs. We thus identified Prdm6 as a factor that is essential for the physiological control of cardiovascular development.

Increased expression of BIN1 mediates Alzheimer genetic risk by modulating tau pathology.

Genome-wide association studies (GWAS) have identified a region upstream the BIN1 gene as the most important genetic susceptibility locus in Alzheimer's disease (AD) after APOE. We report that BIN1 transcript levels were increased in AD brains and identified a novel 3 bp insertion allele ∼28 kb upstream of BIN1, which increased (i) transcriptional activity in vitro, (ii) BIN1 expression levels in human brain and (iii) AD risk in three independent case-control cohorts (Meta-analysed Odds ratio of 1.20 (1.14-1.26) (P=3.8 × 10(-11))). Interestingly, decreased expression of the Drosophila BIN1 ortholog Amph suppressed Tau-mediated neurotoxicity in three different assays. Accordingly, Tau and BIN1 colocalized and interacted in human neuroblastoma cells and in mouse brain. Finally, the 3 bp insertion was associated with Tau but not Amyloid loads in AD brains. We propose that BIN1 mediates AD risk by modulating Tau pathology.

Chronic treatment with a novel γ-secretase modulator, JNJ-40418677, inhibits amyloid plaque formation in a mouse model of Alzheimer's disease.

BACKGROUND AND PURPOSE: γ-Secretase modulators represent a promising therapeutic approach for Alzheimer's disease (AD) because they selectively decrease amyloid ß 42 (Aß42), a particularly neurotoxic Aß species that accumulates in plaques in the brains of patients with AD. In the present study, we describe the in vitro and in vivo pharmacological properties of a potent novel γ-secretase modulator, 2-(S)-(3,5-bis(4-(trifluoromethyl)phenyl)phenyl)-4-methylpentanoic acid (JNJ-40418677). EXPERIMENTAL APPROACH: The potency and selectivity of JNJ-40418677 for Aß reduction was investigated in human neuroblastoma cells, rat primary neurones and after treatment with single oral doses in non-transgenic mouse brains. To evaluate the effect of JNJ-40418677 on plaque formation, Tg2576 mice were treated from 6 until 13 months of age via the diet. KEY RESULTS: JNJ-40418677 selectively reduced Aß42 secretion in human neuroblastoma cells and rat primary neurones, but it did not inhibit Notch processing or formation of other amyloid precursor protein cleavage products. Oral treatment of non-transgenic mice with JNJ-40418677 resulted in an excellent brain penetration of the compound and a dose- and time-dependent decrease of brain Aß42 levels. Chronic treatment of Tg2576 mice with JNJ-40418677 reduced brain Aß levels, the area occupied by plaques and plaque number in a dose-dependent manner compared with transgenic vehicle-treated mice. CONCLUSIONS AND IMPLICATIONS: JNJ-40418677 selectively decreased Aß42 production, showed an excellent brain penetration after oral administration in mice and lowered brain Aß burden in Tg2576 mice after chronic treatment. JNJ-40418677 therefore warrants further investigation as a potentially effective disease-modifying therapy for AD.

Immunoglobulin heavy chain locus chromosomal translocations in B-cell precursor acute lymphoblastic leukemia: rare clinical curios or potent genetic drivers?

Chromosomal translocations involving the immunoglobulin heavy chain (IGH) locus define common subgroups of B-cell lymphoma but are rare in B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Recent fluorescent in situ hybridization and molecular cloning studies have identified several novel IGH translocations involving genes that play important roles in normal hemopoiesis, including the cytokine receptor genes CRLF2 and EPOR, all members of the CCAAT enhancer-binding protein gene family, as well as genes not normally expressed in hemopoietic cells including inhibitor of DNA binding 4. IGH translocation results in deregulated target gene expression because of juxtaposition with IGH transcriptional enhancers. However, many genes targeted by IGH translocations are also more commonly deregulated in BCP-ALL as a consequence of other genetic or epigenetic mechanisms. For example, interstitial genomic deletions also result in deregulated CRLF2 expression, whereas EPOR expression is deregulated as a consequence of the ETV6-RUNX1 fusion. The possible clinical importance of many of the various IGH translocations in BCP-ALL remains to be determined from prospective studies, but CRLF2 expression is associated with a poor prognosis. Despite their rarity, IGH chromosomal translocations in BCP-ALL therefore define not only new mechanisms of B-cell transformation but also clinically important subgroups of disease and suggest new targeted therapeutic approaches.

t(6;14)(p22;q32): a new recurrent IGH@ translocation involving ID4 in B-cell precursor acute lymphoblastic leukemia (BCP-ALL).

Translocations involving the immunoglobulin heavy chain locus (IGH@) at chromosome band 14q32 are common in mature B-cell neoplasms, but are rare in B-cell precursor acute lymphoblastic leukemia (BCP-ALL). Here, we report the translocation, t(6;14)(p22;q32), involving IGH@ as a novel recurrent translocation in 13 BCP-ALL patients. Fluorescence in situ hybridization and long-distance inverse polymerase chain reaction (PCR) identified ID4 as the partner gene. Breakpoints were scattered over a 19kb region centromeric of ID4. Quantitative real-time PCR showed up-regulation of ID4 mRNA. All patients had deletions of CDKN2A and PAX5 located on the short arm of chromosome 9, frequently as a result of an isochromosome, i(9)(q10) (9/13, 69%). This study defines a new subgroup of BCP-ALL characterized by ID4 over-expression and CDKN2A and PAX5 deletions. Preliminary survival data suggest that this subgroup may be associated with a good response to therapy.

Homozygous deletions localize novel tumor suppressor genes in B-cell lymphomas.

Integrative genomic and gene-expression analyses have identified amplified oncogenes in B-cell non-Hodgkin lymphoma (B-NHL), but the capability of such technologies to localize tumor suppressor genes within homozygous deletions remains unexplored. Array-based comparative genomic hybridization (CGH) and gene-expression microarray analysis of 48 cell lines derived from patients with different B-NHLs delineated 20 homozygous deletions at 7 chromosome areas, all of which contained tumor suppressor gene targets. Further investigation revealed that only a fraction of primary biopsies presented inactivation of these genes by point mutation or intragenic deletion, but instead some of them were frequently silenced by epigenetic mechanisms. Notably, the pattern of genetic and epigenetic inactivation differed among B-NHL subtypes. Thus, the P53-inducible PIG7/LITAF was silenced by homozygous deletion in primary mediastinal B-cell lymphoma and by promoter hypermethylation in germinal center lymphoma, the proapoptotic BIM gene presented homozygous deletion in mantle cell lymphoma and promoter hypermethylation in Burkitt lymphoma, the proapoptotic BH3-only NOXA was mutated and preferentially silenced in diffuse large B-cell lymphoma, and INK4c/P18 was silenced by biallelic mutation in mantle-cell lymphoma. Our microarray strategy has identified novel candidate tumor suppressor genes inactivated by genetic and epigenetic mechanisms that substantially vary among the B-NHL subtypes.

Five members of the CEBP transcription factor family are targeted by recurrent IGH translocations in B-cell precursor acute lymphoblastic leukemia (BCP-ALL).

CCAAT enhancer-binding protein (CEBP) transcription factors play pivotal roles in proliferation and differentiation, including suppression of myeloid leukemogenesis. Mutations of CEBPA are found in a subset of acute myeloid leukemia (AML) and in some cases of familial AML. Here, using cytogenetics, fluorescence in situ hybridization (FISH), and molecular cloning, we show that 5 CEBP gene family members are targeted by recurrent IGH chromosomal translocations in BCP-ALL. Ten patients with t(8;14)(q11;q32) involved CEBPD on chromosome 8, and 9 patients with t(14;19)(q32;q13) involved CEBPA, while a further patient involved CEBPG, located 71 kb telomeric of CEBPA in chromosome band 19q13; 4 patients with inv(14)(q11q32)/t(14;14)(q11;q32) involved CEBPE and 3 patients with t(14;20)(q32;q13) involved CEBPB. In 16 patients the translocation breakpoints were cloned using long-distance inverse-polymerase chain reaction (LDI-PCR). With the exception of CEBPD breakpoints, which were scattered within a 43-kb region centromeric of CEBPD, translocation breakpoints were clustered immediately 5' or 3' of the involved CEBP gene. Except in 1 patient with t(14;14)(q11;q32), the involved CEBP genes retained germ-line sequences. Quantitative reverse transcription (RT)-PCR showed overexpression of the translocated CEBP gene. Our findings implicate the CEBP gene family as novel oncogenes in BCP-ALL, and suggest opposing functions of CEBP dysregulation in myeloid and lymphoid leukemogenesis.

Characterization of 8p21.3 chromosomal deletions in B-cell lymphoma: TRAIL-R1 and TRAIL-R2 as candidate dosage-dependent tumor suppressor genes.

Deletions of chromosome 8p are a recurrent event in B-cell non-Hodgkin lymphoma (B-NHL), suggesting the presence of a tumor suppressor gene. We have characterized these deletions using comparative genomic hybridization to microarrays, fluorescence in situ hybridization (FISH) mapping, DNA sequencing, and functional studies. A minimal deleted region (MDR) of 600 kb was defined in chromosome 8p21.3, with one mantle cell lymphoma cell line (Z138) exhibiting monoallelic deletion of 650 kb. The MDR extended from bacterial artificial chromosome (BAC) clones RP11-382J24 and RP11-109B10 and included the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor gene loci. Sequence analysis of the individual expressed genes within the MDR and DNA sequencing of the entire MDR in Z138 did not reveal any mutation. Gene expression analysis and quantitative reverse transcriptase-polymerase chain reaction (QRT-PCR) showed down-regulation of TRAIL-R1 and TRAIL-R2 receptor genes as a consistent event in B-NHL with 8p21.3 loss. Epigenetic inactivation was excluded via promoter methylation analysis. In vitro studies showed that TRAIL-induced apoptosis was dependent on TRAIL-R1 and/or -R2 dosage in most tumors. Resistance to apoptosis of cell lines with 8p21.3 deletion was reversed by restoration of TRAIL-R1 or TRAIL-R2 expression by gene transfection. Our data suggest that TRAIL-R1 and TRAIL-R2 act as dosage-dependent tumor suppressor genes whose monoallelic deletion can impair TRAIL-induced apoptosis in B-cell lymphoma.

Cloning of immunoglobulin chromosomal translocations by long-distance inverse polymerase chain reaction.

Many subtypes of B-cell malignancy are characterized by chromosomal translocations that target the immunoglobulin loci. Molecular cloning of such translocations continues to allow the identification of genes whose deregulated expression plays a pivotal role in the pathogenesis of B-cell malignancy. The clustering of breakpoints within the immunoglobulin loci has allowed the development of rapid and robust polymerase chain reaction methods for cloning. We discuss in this chapter the use of long-distance inverse polymerase chain reaction methods to clone immunoglobulin chromosomal translocation breakpoints from clinical material. These methods have been successfully applied to several other types of chromosomal translocation including those involving other genes such as BCL6, ETV6, and MYC.

Rapid amplification of immunoglobulin heavy chain switch (IGHS) translocation breakpoints using long-distance inverse PCR.

Molecular cloning of immunoglobulin heavy chain (IGH) translocation breakpoints identifies genes of biological importance in the development of normal and malignant B cells. Long-distance inverse PCR (LDI-PCR) was first applied to amplification of IGH gene translocations targeted to the joining (IGHJ) regions. We report here successful amplification of the breakpoint of IGH translocations targeted to switch (IGHS) regions by LDI-PCR. To detect IGHS translocations, Southern blot assays using 5' and 3' switch probes were performed. Illegitimate Smu rearrangements were amplified from the 5' end (5'Smu LDI-PCR) from the alternative derivative chromosome, and those of Sgamma or Salpha were amplified from the 3' end (3'Sgamma or 3'alpha LDI-PCR) from the derivative chromosome 14. Using a combination of these methods, we have succeeded in amplifying IGHS translocation breakpoints involving FGFR3/MMSET on 4p16, BCL6 on 3q27, MYC on 8q24, IRTA1 on 1q21 and PAX5 on 9p13 as well as BCL11A on 2p13 and CCND3 on 6p21. The combination of LDI-PCR for IGHJ and IGHS allows rapid molecular cloning of almost all IGH gene translocation breakpoints.

Proteomic analysis of the cell-surface membrane in chronic lymphocytic leukemia: identification of two novel proteins, BCNP1 and MIG2B.

B-cell-specific plasma-membrane proteins are potential targets for either small molecule or antibody-based therapies. We have sought to annotate proteins expressed at the cell surface membrane in patients with chronic lymphocytic leukemia (CLL) using plasma-membrane-based proteomic analysis to identify previously uncharacterized and potentially B-cell-specific proteins. Proteins from plasma-membrane fractions were separated on one-dimensional gels and trypsinized fractions subjected to high-throughput MALDI-TOF mass spectrometry. Using this method, many known B-cell surface antigens were detected, but also known proteins not previously described in this disease or in this cellular compartment, including cell surface receptors, membrane-associated enzymes and secreted proteins, and completely unknown proteins. To validate the method, we show that BLK, a B-cell-specific kinase, is located in the CLL-plasma-membrane fraction. We also describe two novel proteins (MIG2B and B-cell novel protein #1, BCNP1), which are expressed preferentially in B cells. MIG2B is in a highly conserved and defined gene family containing two plasma-membrane-binding ezrin/radixin/moesin domains and a pleckstrin homology domain; the Caenorhabditis elegans homolog (UNC-112) is a membrane-associated protein that colocalizes with integrin at cell-matrix adhesion complexes. BCNP1 is a completely unknown protein with three predicted transmembrane domains, with three alternatively spliced final exons. Proteomic analysis may thus define new potential therapeutic targets.

A comparison of the effects of lamotrigine on neuroma-induced action potential firing and normal behaviour in rat: implications for establishing a pre-clinical 'therapeutic index'.

The effects of lamotrigine on rat neuroma and behavioural paradigms were evaluated to determine a pre-clinical therapeutic index. Lamotrigine blocked neuroma-induced burst pattern firing at a free plasma concentration of 13.7+/-1.7 microM (n=5). Oral dosing of lamotrigine (50-200 mg/kg) had no significant effects on behaviour but measurements of plasma concentrations of free drug showed non-linear oral absorption and lower than predicted drug levels (5-27 microM). Given intravenously (10-100 mg/kg), lamotrigine did affect behaviour at a free plasma concentration of 42.0 microM (n=2). By comparing free plasma concentrations, a therapeutic index of 3 was calculated, which is lower than published data based on comparing oral doses. We propose that a therapeutic index should only be derived with reference to plasma drug concentrations to prevent non-linear or incomplete drug absorption from confounding accurate estimation.

Characterization of human HtrA2, a novel serine protease involved in the mammalian cellular stress response.

Human HtrA2 is a novel member of the HtrA serine protease family and shows extensive homology to the Escherichia coli HtrA genes that are essential for bacterial survival at high temperatures. HumHtrA2 is also homologous to human HtrA1, also known as L56/HtrA, which is differentially expressed in human osteoarthritic cartilage and after SV40 transformation of human fibroblasts. HumHtrA2 is upregulated in mammalian cells in response to stress induced by both heat shock and tunicamycin treatment. Biochemical characterization of humHtrA2 shows it to be predominantly a nuclear protease which undergoes autoproteolysis. This proteolysis is abolished when the predicted active site serine residue is altered to alanine by site-directed mutagenesis. In human cell lines, it is present as two polypeptides of 38 and 40 kDa. HumHtrA2 cleaves beta-casein with an inhibitor profile similar to that previously described for E. coli HtrA, in addition to an increase in beta-casein turnover when the assay temperature is raised from 37 to 45 degrees C. The biochemical and sequence similarities between humHtrA2 and its bacterial homologues, in conjunction with its nuclear location and upregulation in response to tunicamycin and heat shock suggest that it is involved in mammalian stress response pathways.

A human homolog of angiotensin-converting enzyme. Cloning and functional expression as a captopril-insensitive carboxypeptidase.

A novel human zinc metalloprotease that has considerable homology to human angiotensin-converting enzyme (ACE) (40% identity and 61% similarity) has been identified. This metalloprotease (angiotensin-converting enzyme homolog (ACEH)) contains a single HEXXH zinc-binding domain and conserves other critical residues typical of the ACE family. The predicted protein sequence consists of 805 amino acids, including a potential 17-amino acid N-terminal signal peptide sequence and a putative C-terminal membrane anchor. Expression in Chinese hamster ovary cells of a soluble, truncated form of ACEH, lacking the transmembrane and cytosolic domains, produces a glycoprotein of 120 kDa, which is able to cleave angiotensin I and angiotensin II but not bradykinin or Hip-His-Leu. In the hydrolysis of the angiotensins, ACEH functions exclusively as a carboxypeptidase. ACEH activity is inhibited by EDTA but not by classical ACE inhibitors such as captopril, lisinopril, or enalaprilat. Identification of the genomic sequence of ACEH has shown that the ACEH gene contains 18 exons, of which several have considerable size similarity with the first 17 exons of human ACE. The gene maps to chromosomal location Xp22. Northern blotting analysis has shown that the ACEH mRNA transcript is approximately 3. 4 kilobase pairs and is most highly expressed in testis, kidney, and heart. This is the first report of a mammalian homolog of ACE and has implications for our understanding of cardiovascular and renal function.

Expression, purification, and functional analysis of the human serine protease HtrA2.

HumHtrA2 or Omi is a recently described member of a novel family of mammalian serine proteases homologous to the Escherichia coli htrA gene product. Although the physiological function of members of this new family is unclear, the current understanding is that as well as being involved with the degradation aberrantly folded proteins during conditions of cellular stress, they may possess a chaperone-like role under normal conditions. In this report we describe the overexpression of humHtrA2 in two heterologous systems comparing the merits of each. We found that molecular analysis of processing events in Sf9 cells allowed us to revisit E. coli expression systems which were initially unsuccessful. Using E. coli we were able to produce milligram amounts of >90% pure recombinant enzyme as determined by SDS-PAGE gels. By means of fluorescently labeled substrates alpha- and beta-casein and zymography, the proteolytic activity of recombinant HumHtrA2 was also demonstrated.

Fractionation and characterization of oligomeric, protofibrillar and fibrillar forms of beta-amyloid peptide.

The beta-amyloid (Abeta) peptide, a major component of senile plaques in Alzheimer's disease brain, has been shown previously to undergo a process of polymerization to produce neurotoxic forms of amyloid. Recent literature has attempted to define precisely the form of Abeta responsible for its neurodegenerative properties. In the present study we describe a novel density-gradient centrifugation method for the isolation and characterization of structurally distinct polymerized forms of Abeta peptide. Fractions containing protofibrils, fibrils, sheet structures and low molecular mass oligomers were prepared. The fractionated forms of Abeta were characterized structurally by transmission electron microscopy. The effects on cell viability of these fractions was determined in the B12 neuronal cell line and hippocampal neurons. Marked effects on cell viability in the cells were found to correspond to the presence of protofibrillar and fibrillar structures, but not to monomeric peptide or sheet-like structures of polymerized Abeta. Biological activity correlated with a positive reaction in an immunoassay that specifically detects protofibrillar and fibrillar Abeta; those fractions that were immunoassay negative had no effect on cell viability. These data suggest that the effect of Abeta on cell viability is not confined to a single conformational form but that both fibrillar and protofibrillar species have the potential to be active in this assay.

Development of Neoepitope Antibodies Against the ß-Secretase Cleavage Site in the Amyloid Precursor Protein.

A detailed understanding of the biochemical events leading to the proteolytic excision of the ß-amyloid peptide (A ß) from the amyloid precursor protein (APP) has eluded many researchers. This is largely because the measurement of the various APP processing products is technically challenging owing to their low levels of production in in vitro and in vivo test systems. Sequence analysis of products in cell cultures, cerebrospinal fluid (CSF), and amyloid plaques has been used to predict the major cleavage sites resulting from the ß- and γ-secretase proteolytic activities that release the Aß peptide from APP (1 -3). More routine identification of the secretase activities has relied on the specificity and sensitivity of antibodies raised to the predicted cleavage products and has been impeded by the difficulties associated with the generation of such reagents.

Cleavage of Alzheimer's amyloid precursor protein by alpha-secretase occurs at the surface of neuronal cells.

The amyloid precursor protein (APP) is proteolytically processed predominantly by alpha-secretase to release the ectodomain (sAPPalpha). In this study, we have addressed the cellular location of the constitutive alpha-secretase cleavage of endogenous APP in a neuronal cell line. Incubation of the neuroblastoma cell line IMR32 at 20 degrees C prevented the secretion into the medium of soluble wild-type APP cleaved by alpha-secretase as revealed by both immunoelectrophoretic blot analysis with a site-specific antibody and immunoprecipitation following metabolic labeling of the cells. No sAPPalpha was detected in the cell lysates following incubation of the cells at 20 degrees C, indicating that alpha-secretase does not cleave APP in the secretory pathway prior to or within the trans-Golgi network. Parallel studies using an antibody that recognizes specifically the neoepitope revealed on soluble APP cleaved by beta-secretase indicated that this enzyme was acting intracellularly. alpha-Secretase is a zinc metalloproteinase susceptible to inhibition by hydroxamate-based compounds such as batimastat [Parvathy, S., et al. (1998) Biochemistry 37, 1680-1685]. Incubation of the cells with a cell-impermeant, biotinylated hydroxamate inhibitor inhibited the release of sAPPalpha by >92%, indicating that alpha-secretase is cleaving APP almost exclusively at the cell surface. The observation that alpha-secretase cleaves APP at the cell surface, while beta-secretase can act earlier in the secretory pathway within the neuronal cell line indicates that there must be strict control mechanisms in place to ensure that APP is normally cleaved primarily by alpha-secretase in the nonamyloidogenic pathway to produce the neuroprotective sAPPalpha.

Alzheimer's disease: correlation of the suppression of beta-amyloid peptide secretion from cultured cells with inhibition of the chymotrypsin-like activity of the proteasome.

Peptide aldehyde inhibitors of the chymotrypsin-like activity of the proteasome (CLIP) such as N-acetyl-Leu-Leu-Nle-H (or ALLN) have been shown previously to inhibit the secretion of beta-amyloid peptide (A beta) from cells. To evaluate more fully the role of the proteasome in this process, we have tested the effects on A beta formation of a much wider range of peptide-based inhibitors of CLIP than published previously. The inhibitors tested included several peptide boronates, some of which proved to be the most potent peptide-based inhibitors of beta-amyloid production reported so far. We found that the ability of the peptide aldehyde and boronate inhibitors to suppress A beta formation from cells correlated extremely well with their potency as CLIP inhibitors. Thus, we conclude that the proteasome may be involved either directly or indirectly in A beta formation.