Identification of highly selective SIK1/2 inhibitors that modulate innate immune activation and suppress intestinal inflammation

The salt-inducible kinases (SIK) 1-3 are key regulators of pro- versus anti-inflammatory cytokine responses during innate immune activation. The lack of highly SIK-family or SIK isoform-selective inhibitors suitable for repeat, oral dosing has limited the study of the optimal SIK isoform selectivity profile for suppressing inflammation in vivo. To overcome this challenge, we devised a structure-based design strategy for developing potent SIK inhibitors that are highly selective against other kinases by engaging two differentiating features of the SIK catalytic site. This effort resulted in SIK1/2-selective probes that inhibit key intracellular proximal signaling events including reducing phosphorylation of the SIK substrate cAMP response element binding protein (CREB) regulated transcription coactivator 3 (CRTC3) as detected with an internally generated phospho-Ser329-CRTC3-specific antibody. These inhibitors also suppress production of pro-inflammatory cytokines while inducing anti-inflammatory interleukin-10 in activated human and murine myeloid cells and in mice following a lipopolysaccharide challenge. Oral dosing of these compounds ameliorates disease in a murine colitis model. These findings define an approach to generate highly selective SIK1/2 inhibitors and establish that targeting these isoforms may be a useful strategy to suppress pathological inflammation.

Identification of a new Corin atrial natriuretic peptide-converting enzyme substrate: Agouti-signaling protein (ASIP)

Corin is a transmembrane tethered enzyme best known for processing the hormone atrial natriuretic peptide (ANP) in cardiomyocytes to control electrolyte balance and blood pressure. Loss of function mutations in Corin prevent ANP processing and lead to hypertension. Curiously, Corin loss of function variants also result in lighter coat color pigmentation in multiple species. Corin pigmentation effects are dependent on a functional Agouti locus encoding the agouti-signaling protein (ASIP) based on a genetic interaction. However, the nature of this conserved role of Corin has not been defined. Here we report that ASIP is a direct proteolytic substrate of the Corin enzyme.

Endothelial ARHGEF26 is an angiogenic factor promoting VEGF signalling

AIMS

Genetic studies have implicated the ARHGEF26 locus in the risk of coronary artery disease (CAD). However, the causal pathways by which DNA variants at the ARHGEF26 locus confer risk for CAD are incompletely understood. We sought to elucidate the mechanism responsible for the enhanced risk of CAD associated with the ARHGEF26 locus.

METHODS AND RESULTS

In a conditional analysis of the ARHGEF26 locus, we show that the sentinel CAD-risk signal is significantly associated with various non-lipid vascular phenotypes. In human endothelial cell (EC), ARHGEF26 promotes the angiogenic capacity, and interacts with known angiogenic factors and pathways. Quantitative mass spectrometry showed that one CAD-risk coding variant, rs12493885 (p.Val29Leu), resulted in a gain-of-function ARHGEF26 that enhances proangiogenic signalling and displays enhanced interactions with several proteins partially related to the angiogenic pathway. ARHGEF26 is required for endothelial angiogenesis by promoting macropinocytosis of Vascular Endothelial Growth Factor Receptor 2 (VEGFR2) on cell membrane and is crucial to Vascular Endothelial Growth Factor (VEGF)-dependent murine vessel sprouting ex vivo. In vivo, global or tissue-specific deletion of ARHGEF26 in EC, but not in vascular smooth muscle cells, significantly reduced atherosclerosis in mice, with enhanced plaque stability.

CONCLUSIONS

Our results demonstrate that ARHGEF26 is involved in angiogenesis signaling, and that DNA variants within ARHGEF26 that are associated with CAD risk could affect angiogenic processes by potentiating VEGF-dependent angiogenesis.

Single-nucleus profiling of human dilated and hypertrophic cardiomyopathy

Heart failure encompasses a heterogeneous set of clinical features that converge on impaired cardiac contractile function1,2 and presents a growing public health concern. Previous work has highlighted changes in both transcription and protein expression in failing hearts3,4, but may overlook molecular changes in less prevalent cell types. Here we identify extensive molecular alterations in failing hearts at single-cell resolution by performing single-nucleus RNA sequencing of nearly 600,000 nuclei in left ventricle samples from 11 hearts with dilated cardiomyopathy and 15 hearts with hypertrophic cardiomyopathy as well as 16 non-failing hearts. The transcriptional profiles of dilated or hypertrophic cardiomyopathy hearts broadly converged at the tissue and cell-type level. Further, a subset of hearts from patients with cardiomyopathy harbour a unique population of activated fibroblasts that is almost entirely absent from non-failing samples. We performed a CRISPR-knockout screen in primary human cardiac fibroblasts to evaluate this fibrotic cell state transition; knockout of genes associated with fibroblast transition resulted in a reduction of myofibroblast cell-state transition upon TGFβ1 stimulation for a subset of genes. Our results provide insights into the transcriptional diversity of the human heart in health and disease as well as new potential therapeutic targets and biomarkers for heart failure.

TAILS Identifies Candidate Substrates and Biomarkers of ADAMTS7, a Therapeutic Protease Target in Coronary Artery Disease

Loss-of-function mutations in the secreted enzyme ADAMTS7 (a disintegrin and metalloproteinase with thrombospondin motifs 7) are associated with protection for coronary artery disease. ADAMTS7 catalytic inhibition has been proposed as a therapeutic strategy for treating coronary artery disease; however, the lack of an endogenous substrate has hindered the development of activity-based biomarkers. To identify ADAMTS7 extracellular substrates and their cleavage sites relevant to vascular disease, we used TAILS (terminal amine isotopic labeling of substrates), a method for identifying protease-generated neo-N termini. We compared the secreted proteome of vascular smooth muscle and endothelial cells expressing either full-length mouse ADAMTS7 WT, catalytic mutant ADAMTS7 E373Q, or a control luciferase adenovirus. Significantly enriched N-terminal cleavage sites in ADAMTS7 WT samples were compared to the negative control conditions and filtered for stringency, resulting in catalogs of high confidence candidate ADAMTS7 cleavage sites from our three independent TAILS experiments. Within the overlap of these discovery sets, we identified 24 unique cleavage sites from 16 protein substrates, including cleavage sites in EFEMP1 (EGF-containing fibulin-like extracellular matrix protein 1/Fibulin-3). The ADAMTS7 TAILS preference for EFEMP1 cleavage at the amino acids 123.124 over the adjacent 124.125 site was validated using both endogenous EFEMP1 and purified EFEMP1 in a binary in vitro cleavage assay. Collectively, our TAILS discovery experiments have uncovered hundreds of potential substrates and cleavage sites to explore disease-related biological substrates and facilitate activity-based ADAMTS7 biomarker development.

Rare, Damaging DNA Variants in CORIN and Risk of Coronary Artery Disease: Insights From Functional Genomics and Large-Scale Sequencing Analyses

BACKGROUND

Corin is a protease expressed in cardiomyocytes that plays a key role in salt handling and intravascular volume homeostasis via activation of natriuretic peptides. It is unknown if Corin loss-of-function (LOF) is causally associated with risk of coronary artery disease (CAD).

METHODS

We analyzed all coding CORIN variants in an Italian case-control study of CAD. We functionally tested all 64 rare missense mutations in Western Blot and Mass Spectroscopy assays for proatrial natriuretic peptide cleavage. An expanded rare variant association analysis for Corin LOF mutations was conducted in whole exome sequencing data from 37 799 CAD cases and 212 184 controls.

RESULTS

We observed LOF variants in CORIN in 8 of 1803 (0.4%) CAD cases versus 0 of 1725 controls (P, 0.007). Of 64 rare missense variants profiled, 21 (33%) demonstrated <30% of wild-type activity and were deemed damaging in the 2 functional assays for Corin activity. In a rare variant association study that aggregated rare LOF and functionally validated damaging missense variants from the Italian study, we observed no association with CAD-21 of 1803 CAD cases versus 12 of 1725 controls with adjusted odds ratio of 1.61 ([95% CI, 0.79-3.29]; P=0.17). In the expanded sequencing dataset, there was no relationship between rare LOF variants with CAD was also observed (odds ratio, 1.15 [95% CI, 0.89-1.49]; P=0.30). Consistent with the genetic analysis, we observed no relationship between circulating Corin concentrations with incident CAD events among 4744 participants of a prospective cohort study-sex-stratified hazard ratio per SD increment of 0.96 ([95% CI, 0.87-1.07], P=0.48).

CONCLUSIONS

Functional testing of missense mutations improved the accuracy of rare variant association analysis. Despite compelling pathophysiology and a preliminary observation suggesting association, we observed no relationship between rare damaging variants in CORIN or circulating Corin concentrations with risk of CAD.

Discovery of a First-in-Class Inhibitor of the PRMT5-Substrate Adaptor Interaction

PRMT5 and its substrate adaptor proteins (SAPs), pICln and Riok1, are synthetic lethal dependencies in MTAP-deleted cancer cells. SAPs share a conserved PRMT5 binding motif (PBM) which mediates binding to a surface of PRMT5 distal to the catalytic site. This interaction is required for methylation of several PRMT5 substrates, including histone and spliceosome complexes. We screened for small molecule inhibitors of the PRMT5-PBM interaction and validated a compound series which binds to the PRMT5-PBM interface and directly inhibits binding of SAPs. Mode of action studies revealed the formation of a covalent bond between a halogenated pyridazinone group and cysteine 278 of PRMT5. Optimization of the starting hit produced a lead compound, BRD0639, which engages the target in cells, disrupts PRMT5-RIOK1 complexes, and reduces substrate methylation. BRD0639 is a first-in-class PBM-competitive inhibitor that can support studies of PBM-dependent PRMT5 activities and the development of novel PRMT5 inhibitors that selectively target these functions.

Coronary Disease Association With ADAMTS7 Is Due to Protease Activity

[Figure: see text].

Multimodal small-molecule screening for human prion protein binders

Prion disease is a rapidly progressive neurodegenerative disorder caused by misfolding and aggregation of the prion protein (PrP), and there are currently no therapeutic options. PrP ligands could theoretically antagonize prion formation by protecting the native protein from misfolding or by targeting it for degradation, but no validated small-molecule binders have been discovered to date. We deployed a variety of screening methods in an effort to discover binders of PrP, including 19F-observed and saturation transfer difference (STD) NMR spectroscopy, differential scanning fluorimetry (DSF), DNA-encoded library selection, and in silico screening. A single benzimidazole compound was confirmed in concentration-response, but affinity was very weak (Kd > 1 mm), and it could not be advanced further. The exceptionally low hit rate observed here suggests that PrP is a difficult target for small-molecule binders. Whereas orthogonal binder discovery methods could yield high-affinity compounds, non-small-molecule modalities may offer independent paths forward against prion disease.

Abstract 021: ARHGEF26 is a Novel Genetic Risk Factor for Vascular Inflammation and Coronary Artery Disease

Vascular inflammation drives the initiation and progression of coronary artery disease (CAD). However, the underlying genetic factors are not well understood. We performed a genome-wide association study in UK Biobank testing 9 million DNA variants for association with CAD (4,831 cases, 115,455 controls), followed by a meta-analysis with previous results. We identified ARHGEF26 (Rho guanine nucleotide exchange factor 26) as a novel locus significantly associated with CAD (combined OR=1.08, 95% CI 1.06-1.11, P=1.02 х 10 –9 ). We hypothesized that ARHGEF26 regulates vascular inflammation by affecting the function of vascular cells. Focusing on the haplotype tagged by the lead variant rs12493885 (ARHGEF26 p.Val29Leu), we performed eQTL and allele-specific expression analyses. There is no significant ARHGEF26 transcription alteration or allelic imbalance associated with the risk allele in human coronary artery samples. Promoter luciferase assay showed no significant difference between the reference and alternative haplotypes. In contrast, expression of exogenous Leu29 mutant after depletion of endogenous ARHGEF26 led to rescued phenotypes consistently exceeding those observed with overexpression of wild-type ARHGEF26, including increased leukocyte transendothelial migration, leukocyte adhesion on endothelial cells, and smooth muscle cell proliferation. These data suggest that the CAD-risk allele (Leu29) may lead to a gain of protein function in vascular cells. To identify the molecular mechanism, we compared the nucleotide-exchange activity between the wild-type and mutant proteins and found no significant difference. Evaluation of ARHGEF26 protein stability by cycloheximide chase showed the Leu29 mutant displayed longer half-life than wild-type ARHGEF26, suggesting the gain-of-function phenotypes of Leu29 in cells may be secondary to its resistance to degradation. Quantitative proteomics revealed differential protein interaction between the wild-type and Leu29 ARHGEF26 in endothelial cells, highlighting critical inflammatory pathways impacted by the CAD-risk allele. In summary, our work identified a novel genetic risk factor for CAD, and enabled discovery of novel CAD-causing pathways in vascular inflammation.

Genetic analysis in UK Biobank links insulin resistance and transendothelial migration pathways to coronary artery disease

UK Biobank is among the world’s largest repositories for phenotypic and genotypic information in individuals of European ancestry¹. We performed a genome-wide association study in UK Biobank testing ~9 million DNA sequence variants for association with coronary artery disease (4,831 cases; 115,455 controls) and carried out meta-analysis with previously published results. We identified fifteen novel loci, bringing the total number of coronary artery disease-associated loci to 95. Phenome-wide association scanning revealed that CCDC92 likely affects coronary artery disease through insulin resistance pathways whereas experimental analysis suggests that ARHGEF26 impacts the transendothelial migration of leukocytes.

Point mutations at the catalytic site of PCSK9 inhibit folding, autoprocessing, and interaction with the LDL receptor

Circulating low-density lipoprotein cholesterol (LDLc) is regulated by membrane-bound LDL receptor (LDLr). Upon LDLc and LDLr interaction the complex is internalized by the cell, leading to LDLc degradation and LDLr recycling back to the cell surface. The proprotein convertase subtilisin/kexin type 9 (PCSK9) protein regulates this cycling. PCSK9 is secreted from the cell and binds LDLr. When the complex is internalized, PCSK9 prevents LDLr from shuttling back to the surface and instead targets it for degradation. PCSK9 is a serine protease expressed as a zymogen that undergoes autoproteolysis, though the two resulting protein domains remain stably associated as a heterodimer. This PCSK9 autoprocessing is required for the protein to be secreted from the cell. To date, direct analysis of PCSK9 autoprocessing has proven challenging, as no catalytically active zymogen has been isolated. A PCSK9 loss-of-function point mutation (Q152H) that reduces LDLc levels two-fold was identified in a patient population. LDLc reduction was attributed to a lack of PCSK9(Q152H) autoprocessing preventing secretion of the protein. We have isolated a zymogen form of PCSK9, PCSK9(Q152H), and a related mutation (Q152N), that can undergo slow autoproteolysis. We show that the point mutation prevents the formation of the mature form of PCSK9 by hindering folding, reducing the rate of autoproteolysis, and destabilizing the heterodimeric form of the protein. In addition, we show that the zymogen form of PCSK9 adopts a structure that is distinct from the processed form and is unable to bind a mimetic peptide based on the EGF-A domain of the LDLr.

Single Diastereomer of a Macrolactam Core Binds Specifically to Myeloid Cell Leukemia 1 (MCL1)

A direct binding screen of 100 000 sp(3)-rich molecules identified a single diastereomer of a macrolactam core that binds specifically to myeloid cell leukemia 1 (MCL1). A comprehensive toolbox of biophysical methods was applied to validate the original hit and subsequent analogues and also established a binding mode competitive with NOXA BH3 peptide. X-ray crystallography of ligand bound to MCL1 reveals a remarkable ligand/protein shape complementarity that diverges from previously disclosed MCL1 inhibitor costructures.

New hypotheses about the structure-function of proprotein convertase subtilisin/kexin type 9: analysis of the epidermal growth factor-like repeat A docking site using WaterMap

LDL cholesterol (LDL-C) is cleared from plasma via cellular uptake and internalization processes that are largely mediated by the low-density lipoprotein cholesterol receptor (LDL-R). LDL-R is targeted for lysosomal degradation by association with proprotein convertase subtilisin-kexin type 9 (PCSK9). Gain of function mutations in PCSK9 can result in excessive loss of receptors and dyslipidemia. On the other hand, receptor-sparing phenomena, including loss-of-function mutations or inhibition of PCSK9, can lead to enhanced clearance of plasma lipids. We hypothesize that desolvation and resolvation processes, in many cases, constitute rate-determining steps for protein-ligand association and dissociation, respectively. To test this hypothesis, we analyzed and compared the predicted desolvation properties of wild-type versus gain-of-function mutant Asp374Tyr PCSK9 using WaterMap, a new in silico method for predicting the preferred locations and thermodynamic properties of water solvating proteins ("hydration sites"). We compared these results with binding kinetics data for PCSK9, full-length LDL-R ectodomain, and isolated EGF-A repeat. We propose that the fast k(on) and entropically driven thermodynamics observed for PCSK9-EGF-A binding stem from the functional replacement of water occupying stable PCSK9 hydration sites (i.e., exchange of PCSK9 H-bonds from water to polar EGF-A groups). We further propose that the relatively fast k(off) observed for EGF-A unbinding stems from the limited displacement of solvent occupying unstable hydration sites. Conversely, the slower k(off) observed for EGF-A and LDL-R unbinding from Asp374Tyr PCSK9 stems from the destabilizing effects of this mutation on PCSK9 hydration sites, with a concomitant increase in the persistence of the bound complex.

JNK1 phosphorylates SIRT1 and promotes its enzymatic activity

SIRT1 is a NAD-dependent deacetylase that regulates a variety of pathways including the stress protection pathway. SIRT1 deacetylates a number of protein substrates, including histones, FOXOs, PGC-1α, and p53, leading to cellular protection. We identified a functional interaction between cJUN N-terminal kinase (JNK1) and SIRT1 by coimmunoprecipitation of endogenous proteins. The interaction between JNK1 and SIRT1 was identified under conditions of oxidative stress and required activation of JNK1 via phosphorylation. Modulation of SIRT1 activity or protein levels using nicotinamide or RNAi did not modify JNK1 activity as measured by its ability to phosphorylate cJUN. In contrast, human SIRT1 was phosphorylated by JNK1 on three sites: Ser27, Ser47, and Thr530 and this phosphorylation of SIRT1 increased its nuclear localization and enzymatic activity. Surprisingly, JNK1 phosphorylation of SIRT1 showed substrate specificity resulting in deacetylation of histone H3, but not p53. These findings identify a mechanism for regulation of SIRT1 enzymatic activity in response to oxidative stress and shed new light on its role in the stress protection pathway.

Mice deleted for fatty acid transport protein 5 have defective bile acid conjugation and are protected from obesity

BACKGROUND & AIMS

Fatty Acid Transport Protein 5 (FATP5) is a liver-specific member of the FATP/Slc27 family, which has been shown to exhibit both fatty acid transport and bile acid-CoA ligase activity in vitro. Here, we investigate its role in bile acid metabolism and body weight homeostasis in vivo by using a novel FATP5 knockout mouse model.

METHODS

Bile acid composition was analyzed by mass spectroscopy. Body weight, food intake, energy expenditure, and fat absorption were determined in animals fed either a low- or a high-fat diet.

RESULTS

Although total bile acid concentrations were unchanged in bile, liver, urine, and feces of FATP5 knockout mice, the majority of gallbladder bile acids was unconjugated, and only a small percentage was conjugated. Primary, but not secondary, bile acids were detected among the remaining conjugated forms in FATP5 deletion mice, suggesting a specific requirement for FATP5 in reconjugation of bile acids during the enterohepatic recirculation. Fat absorption in FATP5 deletion mice was largely normal, and only a small increase in fecal fat was observed on a high-fat diet. Despite normal fat absorption, FATP5 deletion mice failed to gain weight on a high-fat diet because of both decreased food intake and increased energy expenditure.

CONCLUSIONS

Our findings reveal an important role for FATP5 in bile acid conjugation in vivo and an unexpected function in body weight homeostasis, which will require further analysis. FATP5 deletion mice provide a new model to study the intersection of bile acid metabolism, lipid metabolism, and body weight regulation.

AMPK as a metabolic switch in rat muscle, liver and adipose tissue after exercise

An increasing body of evidence has revealed that activation of adenosine monophosphate (AMP)-activated protein kinase (AMPK)-activated protein kinase increases fatty acid oxidation by lowering the concentration of malonyl coenzyme A (CoA), an inhibitor of carnitine palmitoyl transferase 1. Studies carried out primarily in skeletal muscle suggest that AMPK modulates the concentration of malonyl CoA by concurrently phosphorylating and inhibiting acetyl CoA carboxylase (ACC), the rate limiting enzyme in malonyl CoA synthesis, and phosphorylating and activating malonyl CoA decarboxylase (MCD), an enzyme involved in its degradation. We have recently observed that AMPK and MCD activities are increased and ACC activity diminished in skeletal muscle, liver and, surprisingly, in adipose tissue 30 min following exercise (treadmill run) in normal rats. In liver and adipose tissue these changes were associated with a decrease in the activity of glycerol-3-phosphate acyltransferase (GPAT), which catalyses the first committed reaction in glycerolipid synthesis and, which like ACC, is phosphorylated and inhibited by AMPK. Similar changes in ACC, MCD and GPAT were observed following the administration of 5-aminoimidazole 4-carboxamide-riboside (AICAR), further indicating that the exercise-induced alterations in these enzymes were AMPK-mediated.

CONCLUSIONS

(1) AMPK plays a major role in regulating lipid metabolism in multiple tissues following exercise. (2) The net effect of its activation is to increase fatty acid oxidation and diminish glycerolipid synthesis. (3) The relevance of these findings to the regulation of muscle glycogen repletion in the post-exercise state and to the demonstrated ability of AMPK activation to decrease adiposity and increase insulin sensitivity in rodents remains to be determined.

Substrate-based design of the first class of angiotensin-converting enzyme-related carboxypeptidase (ACE2) inhibitors

Angiotensin-converting enzyme-related carboxypeptidase (ACE2) is a recently identified zinc metalloprotease with carboxypeptidase activity that was identified using our genomics platform. We implemented a rational design approach to identify potent and selective ACE2 inhibitors. To this end, picomolar inhibitors of ACE2 were designed and synthesized.

Coordinate regulation of malonyl-CoA decarboxylase, sn-glycerol-3-phosphate acyltransferase, and acetyl-CoA carboxylase by AMP-activated protein kinase in rat tissues in response to exercise

Changes in the concentration of malonyl-CoA in many tissues have been related to alterations in the activity of acetyl-CoA carboxylase (ACC), the rate-limiting enzyme in its formation. In contrast, little is known about the physiological role of malonyl-CoA decarboxylase (MCD), an enzyme responsible for malonyl-CoA catabolism. In this study, we examined the effects of voluntary exercise on MCD activity in rat liver, skeletal muscle, and adipose tissue. In addition, the activity of sn-glycerol-3-phosphate acyltransferase (GPAT), which like MCD and ACC can be regulated by AMP-activated protein kinase (AMPK), was assayed. Thirty min after the completion of a treadmill run, MCD activity was increased approximately 2-fold, malonyl-CoA levels were reduced, and ACC and GPAT activities were diminished by 50% in muscle and liver. These events appeared to be mediated via activation of AMPK since: 1) AMPK activity was concurrently increased by exercise in both tissues; 2) similar findings were observed after the injection of 5-amino 4 imidazole carboxamide, an AMPK activator; 3) changes in the activity of GPAT and ACC paralleled that of MCD; and 4) the increase in MCD activity in muscle was reversed in vitro by incubating immunoprecipitated enzyme from the exercised muscle with protein phosphatase 2A, and it was reproduced by incubating immunopurified MCD from resting muscle with purified AMPK. An unexpected finding was that exercise caused similar changes in the activities of ACC, MCD, GPAT, and AMPK and the concentration of malonyl-CoA in adipose tissue.

IN CONCLUSION

MCD, GPAT, and ACC are coordinately regulated by AMPK in liver and adipose tissue in response to exercise, and except for GPAT, also in muscle. The results suggest that AMPK activation plays a major role in regulating lipid metabolism in many cells following exercise. They also suggest that in each of them, it acts to increase fatty acid oxidation and decrease its esterification.

Regulation of fatty acid oxidation and glucose metabolism in rat soleus muscle: effects of AICAR

Previous studies have shown that 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), a cell-permeable activator of AMP-activated protein kinase, increases the rate of fatty acid oxidation in skeletal muscle of fed rats. The present study investigated the mechanism by which this occurs and, in particular, whether changes in the activity of malonyl-CoA decarboxylase (MCD) and the beta-isoform of acetyl-CoA carboxylase (ACC beta) are involved. In addition, the relationship between changes in fatty acid oxidation induced by AICAR and its effects on glucose uptake and metabolism was examined. In incubated soleus muscles isolated from fed rats, AICAR (2 mM) increased fatty acid oxidation (90%) and decreased ACC beta activity (40%) and malonyl-CoA concentration (50%); however, MCD activity was not significantly altered. In soleus muscles from overnight-fasted rats, AICAR decreased ACC beta activity (40%), as it did in fed rats; however, it had no effect on the already high rate of fatty acid oxidation or the low malonyl-CoA concentration. In keeping with its effect on fatty acid oxidation, AICAR decreased glucose oxidation by 44% in fed rats but did not decrease glucose oxidation in fasted rats. It had no effect on glucose oxidation when fatty acid oxidation was inhibited by 2-bromopalmitate. Surprisingly, AICAR did not significantly increase glucose uptake or assayable AMP-activated protein kinase activity in incubated soleus muscles from fed or fasted rats. These results indicate that, in incubated rat soleus muscle, 1) AICAR does not activate MCD or stimulate glucose uptake as it does in extensor digitorum longus and epitrochlearis muscles, 2) the ability of AICAR to increase fatty acid oxidation and diminish glucose oxidation and malonyl-CoA concentration is dependent on the nutritional status of the rat, and 3) the ability of AICAR to diminish assayable ACC activity is independent of nutritional state.

Genotoxic effect of ammonia exposure on workers in a fertilizer factory

Cytogenetic investigations carried out on 22 workers exposed to ammonia in a fertilizer factory showed increased frequency of chromosome aberrations (2.00) and sister chromatid exchanges (5.21). Effect of smoking and/or drinking habits coupled with exposure to ammonia showed higher values of mitotic index, satellite associations and micronuclei in the exposed workers (6.50, 17.4 and 2.20 respectively) as compared to the controls (4.34, 8.11 and 0.14 respectively). The results indicate the genotoxic potential of ammonia gas in the ambient air of the work place.

Effect of sulphur dioxide exposure on human chromosomes

The genotoxic effects of an average concentration of 41.7 mg/m3 of SO2 exposure on 42 workers of a fertilizer factory were investigated. Mitotic index (MI), chromosomal aberrations (CAs), sister-chromatid exchanges (SCEs) and satellite associations (SA) were observed. In SO2-exposed workers, a higher mitotic index (7.09) was recorded in comparison to controls (4.34). The MI, however, declined with duration of exposure. Satellite associations showed a two-fold increase (17.1) as compared to controls (8.11). Among chromosomes, D-G group associations were the highest (7.43%), while 3D type associations were the lowest (0.4%). There was a significant difference (p < 0.05) in the mean frequency of CAs per cell in the exposed workers (3.262%) and the controls (0.833%). The mean frequency of SCEs per cell increased from 3.32 +/- 0.1 in controls to 7.72 +/- 0.19 in the exposed group. The difference was significant (p < 0.05). In smokers, alcoholics and smoker-alcoholics, the frequency of CAs and SCEs per cell was significantly higher than the non-smokers and non-alcoholics, both in the controls and the SO2-exposed workers and showed a correlation with the duration of exposure. SO2 is therefore a clastogenic and genotoxic agent for which necessary precautions must be taken.

Polycyclic aromatic hydrocarbons in C8 isomer aromatic feed: analysis by GC, GC/MS, and GC/FTIR techniques

Polycyclic aromatic hydrocarbons (PAHs), apart from their carcinogenic and mutagenic nature, create many problems in the petrochemical industry due to their tendency toward carbonization. Compounds in C8 aromatic isomer feed are analyzed by means of sample concentration, followed by separation of individual compounds by gas chromatography on a stainless steel OV-101 phase capillary column and identification by gas chromatography/mass spectrometry and gas chromatography/Fourier transform infrared spectroscopy. Various compounds belonging to different classes (mainly monocyclic, dicyclic, and tricyclic aromatics), oxygenated aromatics, and aliphatic saturates are quantified in the concentrated hydrocarbon residue of C8 isomer feed. Both unsubstituted and alkyl substituted ring type compounds are present. Concentrations obtained for PAH compounds in the C8 isomer feed range from 0.2 to 0.42 micrograms/mL.