Liver-specific deficiency of serine palmitoyltransferase subunit 2 decreases plasma sphingomyelin and increases apolipoprotein E levels

Sphingomyelin (SM) is one of the major lipid components of plasma lipoproteins. Serine palmitoyltransferase (SPT) is the key enzyme in SM biosynthesis. Mice totally lacking in SPT are embryonic lethal. The liver is the major site for plasma lipoprotein biosynthesis, secretion, and degradation, and in this study we utilized a liver-specific knock-out approach for evaluating liver SPT activity and also its role in plasma SM and lipoprotein metabolism. We found that a deficiency of liver-specific Sptlc2 (a subunit of SPT) decreased liver SPT protein mass and activity by 95 and 92%, respectively, but had no effect on other tissues. Liver Sptlc2 deficiency decreased plasma SM levels (in both high density lipoprotein and non-high density lipoprotein fractions) by 36 and 35% (p < 0.01), respectively, and increased phosphatidylcholine levels by 19% (p < 0.05), thus increasing the phosphatidylcholine/SM ratio by 77% (p < 0.001), compared with controls. This deficiency also decreased SM levels in the liver by 38% (p < 0.01) and in the hepatocyte plasma membranes (based on a lysenin-mediated cell lysis assay). Liver-specific Sptlc2 deficiency significantly increased hepatocyte apoE secretion and thus increased plasma apoE levels 3.5-fold (p < 0.0001). Furthermore, plasma from Sptlc2 knock-out mice had a significantly stronger potential for promoting cholesterol efflux from macrophages than from wild-type mice (p < 0.01) because of a greater amount of apoE in the circulation. As a result of these findings, we believe that the ability to control liver SPT activity could result in regulation of lipoprotein metabolism and might have an impact on the development of atherosclerosis.

Macrophage sphingomyelin synthase 2 deficiency decreases atherosclerosis in mice

RATIONALE

Sphingomyelin synthase (SMS)2 contributes to de novo sphingomyelin (SM) biosynthesis and plasma membrane SM levels. SMS2 deficiency in macrophages diminishes nuclear factor kappaB and mitogen-activated protein kinase activation induced by inflammatory stimuli.

OBJECTIVE

The effects of SMS2 deficiency on the development of atherosclerosis are investigated.

METHODS AND RESULTS

We measured cholesterol efflux from macrophages of wild-type (WT) and SMS2 knockout (KO) mice. We transplanted SMS2 KO mouse bone marrow into low-density lipoprotein (LDL) receptor (LDLr) knockout mice (SMS2(-/-)-->LDLr(-/-)), creating a mouse model of SMS2 deficiency in the macrophages. We found that SMS2 deficiency caused significant induction of cholesterol efflux in vitro and in vivo. Moreover, we found that SMS2 KO mice had less interleukin-6 and tumor necrosis factor alpha in the circulation before and after endotoxin stimulation, compared with controls. More importantly, after 3 months on a western-type diet, SMS2(-/-)-->LDLr(-/-) mice showed decreased atherosclerotic lesions in the aortic arch, root (57%, P<0.001), and the entire aorta (42%, P<0.01), compared with WT-->LDLr(-/-) mice. Analysis of plaque morphology revealed that SMS2(-/-)-->LDLr(-/-) mice had significantly less necrotic core area (71%, P<0.001), less macrophage content (37%, P<0.01), and more collagen content (35%, P<0.05) in atherosclerotic lesions. We also found that SMS2(-/-)-->LDLr(-/-) mice had significantly lower free cholesterol and cholesteryl ester levels in the brachiocephalic artery than WT-->LDLr(-/-) mice (33 and 52%, P<0.01 and P<0.001, respectively).

CONCLUSIONS

SMS2 deficiency in the macrophages reduces atherosclerosis in mice. Macrophage SMS2 is thus a potential therapeutic target for treatment of this disease.

Sphingomyelin synthase 2 is one of the determinants for plasma and liver sphingomyelin levels in mice

BACKGROUND

It has been proposed that plasma sphingomyelin (SM) plays a very important role in plasma lipoprotein metabolism and atherosclerosis. Sphingomyelin synthase (SMS) is the last enzyme for SM de novo biosynthesis. Two SMS genes, SMS1 and SMS2, have been cloned and characterized.

METHODS AND RESULTS

To evaluate the in vivo role of SMS2 in SM metabolism, we prepared SMS2 knockout (KO) and SMS2 liver-specific transgenic (LTg) mice and studied their plasma SM and lipoprotein metabolism. On a chow diet, SMS2 KO mice showed a significant decrease in plasma SM levels (25%, P<0.05), but no significant changes in total cholesterol, total phospholipids, or triglyceride, compared with wild-type (WT) littermates. On a high-fat diet, SMS2 KO mice showed a decrease in plasma SM levels (28%, P<0.01), whereas SMS2LTg mice showed a significant increase in those levels (29%, P<0.05), but no significant changes in other lipids, compared with WT littermates. Atherogenic lipoproteins from SMS2LTg mice displayed a significantly stronger tendency toward aggregation after mammalian sphingomyelinase treatment, compared with controls. Moreover, SMS2 deficiency significantly increased plasma apoE levels (2.0-fold, P<0.001), whereas liver-specific SMS2 overexpression significantly decreased those levels (1.8-fold, P<0.01). Finally, SMS2 KO mouse plasma promoted cholesterol efflux from macrophages, whereas SMS2LTg mouse plasma prevented it.

CONCLUSIONS

We therefore believe that regulation of liver SMS2 activity could become a promising treatment for atherosclerosis.

Needle sticks injury among nurses involved in patient care: a study in two medical college hospitals of West Bengal

A hospital-based retrospective study on a sample of 228 nurses involved in patient care, in two medical college hospitals of West Bengal, showed that 61.4% of them sustained at least one Needle Stick Injury (NSI) in last 12 months. The risk of such injuries per 1000 nurses per year was found to be 3,280. Out of the most recent injuries among 140 nurses, 92.9% remained unreported to appropriate authorities; in 52.9% events hand gloves were worn by the nurses; only 5% of those nurses received hepatitis B vaccine, 2.1% hepatitis B immunoglobulin and none of them received post exposure prophylaxis for HIV.

Septic abortions: a descriptive study in a teaching hospital at North Bengal, Darjeeling

A hospital based cross sectional study for one year done among 57 diagnosed and admitted septic abortion cases, revealed that 71.9% septic abortions were performed by untrained persons, 63.2% mothers were illiterate, 22.8% mothers were in adolescent age group. Exploratory Laparotomy was needed in 46.3% cases and important complications for referring were severe anaemia and septic shock.

Expression and processing of the Hepatitis E virus ORF1 nonstructural polyprotein

Background

The ORF1 of hepatitis E virus (HEV) encodes a nonstructural polyprotein of ~186 kDa that has putative domains for four enzymes: a methyltransferase, a papain-like cysteine protease, a RNA helicase and a RNA dependent RNA polymerase. In the absence of a culture system for HEV, the ORF1 expressed using bacterial and mammalian expression systems has shown an ~186 kDa protein, but no processing of the polyprotein has been observed. Based on these observations, it was proposed that the ORF1 polyprotein does not undergo processing into functional units. We have studied ORF1 polyprotein expression and processing through a baculovirus expression vector system because of the high level expression and post-translational modification abilities of this system.

Results

The baculovirus expressed ORF1 polyprotein was processed into smaller fragments that could be detected using antibodies directed against tags engineered at both ends. Processing of this ~192 kDa tagged ORF1 polyprotein and accumulation of lower molecular weight species took place in a time-dependent manner. This processing was inhibited by E-64d, a cell-permeable cysteine protease inhibitor. MALDI-TOF analysis of a 35 kDa processed fragment revealed 9 peptide sequences that matched the HEV methyltransferase (MeT), the first putative domain of the ORF1 polyprotein. Antibodies to the MeT region also revealed an ORF1 processing pattern identical to that observed for the N-terminal tag.

Conclusion

When expressed through baculovirus, the ORF1 polyprotein of HEV was processed into smaller proteins that correlated with their proposed functional domains. Though the involvement of non-cysteine protease(s) could not be be ruled out, this processing mainly depended upon a cysteine protease.

In vivo enhancement of nucleopolyhedrovirus of oriental Armyworm, Mythimna separata using spindles from Helicoverpa armigera entomopoxvirus

When the third instar larvae of M. separata were exposed to eight varying concentrations of polyhedral occlusion bodies (POB's) of nucleopolyhedrovirus of M. separata (MsNPV) ranging from 2.6 x 10(-1) to 2.6 x 10(8) POB's/ml, the percent mortality and incubation period ranged from 16-100% and 14 to 9 days respectively. On the other hand when the same third instar larvae of M. separata were exposed to only five varying concentration of POB's of MsNPV ranging from 2.6 x 10(2) to 2.6 x 10(6), POB's/ml along with a constant dose of entomopox viral spindles from Helicoverpa armigera, the per cent mortality ranged from 63 to 100% with reduction in incubation period from 7 to 4 days respectively. The enhancement index (log10) of the virus was 2.76 or reduction of more than 500 times in LC50. The ability and the mechanism of the spindles from H. armigera entomopoxvirus to enhance the infectivity of MsNPV has been discussed.

Par-4 drives trafficking and activation of Fas and Fasl to induce prostate cancer cell apoptosis and tumor regression

Prostate cancer cells are generally resistant to apoptosis by conventional therapy. During a search for molecules that may overcome prostate cancer cell survival mechanisms, we identified the prostate apoptosis response-4 (Par-4) gene. Par-4 induced apoptosis of selective prostate cancer cells PC-3, DU-145, and TSU-Pr and caused tumor regression by inhibition of NF-kappaB activity and cell membrane trafficking of Fas and FasL that leads to the activation of the Fas-Fas-associated death domain-caspase-8 pro-death pathway. Neither Fas pathway activation alone nor inhibition of NF-kappaB activity with IkappaB-super repressor was sufficient to induce apoptosis of prostate cancer cells. Coregulation of these two pathways was essential and sufficient for Par-4 to induce apoptosis. On the other hand, prostate cancer cells LNCaP or normal prostatic epithelial cells that were resistant to apoptosis by Par-4 did not show Fas or FasL trafficking. These findings identify a mechanism of apoptosis by Par-4 and suggest that Par-4 may have therapeutic potential.

Beneficial effects of continuous subcutaneous insulin infusion in older patients with long-standing type 1 diabetes

OBJECTIVE

To assess the effect of continuous subcutaneous insulin infusion (CSII) on glycemic control, hypoglycemia, and daily insulin requirements in five older patients with long-standing type 1 diabetes previously treated with multiple-dose insulin injections (MDII).

METHODS

We undertook a retrospective analysis of five older patients (three women and two men) with type 1 diabetes and a mean age of 66.4 years (range, 57 to 76). The mean duration of disease was 33 years (range, 18 to 49), and all patients had suboptimal glycemic control (glycosylated hemoglobin or HbA(1c) >8.0%), presence of microvascular complications, and unacceptably frequent hypoglycemia during MDII therapy. A diabetes care team monitored their clinical course after their treatment was changed to a CSII regimen. Data pertaining to HbA(1c), severe hypoglycemia, and insulin dose before and after conversion to CSII were compared with use of paired t tests.

RESULTS

After initiation of CSII therapy, the mean HbA(1c) value decreased from 9.16% to 7.6% (P<0.0025), the rate of severe hypoglycemia decreased from 3.2 episodes to 0.4 episode per year (P<0.02), and the mean total daily insulin dose was reduced from 44.9 IU to 32.4 IU (P<0.05) during a mean duration of 12.6 months of CSII therapy.

CONCLUSION

Insulin pump therapy can prove highly beneficial in older patients with type 1 diabetes by improving glycemic control, reducing hypoglycemic episodes and insulin dosage, and possibly increasing treatment satisfaction. These changes can potentially prevent morbidity and prove to be cost-effective. For implementation of pump conversion to be safe and successful, careful patient selection, proper education, and ongoing support through a comprehensive diabetes education and management program are imperative. Future reports of experience with CSII in elderly patients should help to elucidate its promising advantages in this patient population and provide guidelines for use.

Increased risk of antituberculosis drug-induced hepatotoxicity in individuals with glutathione S-transferase M1 'null' mutation

BACKGROUND

Pathogenesis and genetic factors influencing predisposition to antituberculosis drug (ATD)-induced hepatotoxicity are not clear. Polymorphism at the genetic locus of a drug and xenobiotic compound metabolizing enzyme, N-acetyltransferase type 2 (NAT2), is reported to be associated with the excess generation of toxic reactive metabolites. Polymorphisms at the glutathione S-transferase (GST) loci (GSTM1 and GSTT1) are involved in the detoxification of these toxic metabolites in the human body to a lesser extent. We have examined whether polymorphisms at these loci are associated with the risk of ATD-induced hepatotoxicity.

METHODS

In this case-control study, 33 pulmonary tuberculosis patients with ATD-induced hepatotoxicity and 33 pulmonary tuberculosis patients receiving ATD drugs without any evidence of hepatotoxicity were considered as cases and controls, respectively. Point mutations at NAT2 and homozygous 'null' mutations at GSTM1 and GSTT1 genes were looked into genomic DNA, isolated from peripheral blood mononuclear cells by using polymerase chain reaction (PCR).

RESULTS

The frequency of homozygous 'null' mutation at the GSTM1 gene was significantly higher among cases (n = 17, 52%) than controls (n = 8, 24%) (P < 0.05, relative risk 2.13, 95% CI: 1.25-3.10). Frequencies of mutations at GSTT1 and NAT2 genes did not differ significantly between cases and controls.

CONCLUSION

Homozygous 'null' mutation at the GSTM1 gene might predispose an individual to ATD-induced hepatotoxicity.

Ethnic differences in distributions of GSTM1 and GSTT1 homozygous "null" genotypes in India

We estimated the frequencies of GSTM1 and GSTT1 "null" homozygotes in 10 different ethnic populations of India by a genotyping method based on polymerase chain reaction. These populations, inhabiting diverse geographical locations and occupying various positions in the sociocultural hierarchy, were represented by a sample of 299 unrelated individuals. Frequencies of GSTM1 and GSTT1 "null" homozygotes varied from 20% to 79% and 3% to 39%, respectively, across the study populations. Maximum frequencies of GSTM1 and GSTT1 "null" homozygotes (79% and 39%, respectively) have been observed in the same population (Jamatia). Frequencies of homozygous "null" genotypes at the GSTM1 and GSTT1 loci show a significant positive correlation in these populations, which is contrary to expectations. A possible implication is that the two enzymes are working in tandem, instead of working in a complementary way.

Coupling of nerve growth factor to its receptor: inhibition by anti-GM3 ganglioside antibody

1. Normal differentiation of PC 12 cells and dorsal root ganglionic neurons in culture need nerve growth factor (NGF) for their neurite outgrowth. 2. An antibody against GM3 ganglioside was found to inhibit the nerve growth factor mediated neurite formation of both the cells in vitro significantly. 3. Further analysis revealed that the binding of 125I-NGF to live PC 12 cells could be markedly inhibited by anti-GM3 antibody in a dose dependent manner. 4. Scatchard analysis revealed that in the presence of anti-GM3 antibody only some low affinity binding sites were available for NGF-high affinity binding sites were totally blocked. 5. These results further strengthen the hypothesis that anti-GM3 antibody affects neuronal cell growth by interfering with the coupling of growth factors to their cell surface receptors.

Clinical and immune responses in resected colon cancer patients treated with anti-idiotype monoclonal antibody vaccine that mimics the carcinoembryonic antigen

PURPOSE

We generated an anti-idiotype antibody, designated CeaVac, that is an internal image of the carcinoembryonic antigen (CEA). We previously demonstrated that the majority of patients with advanced colorectal cancer generate specific anti-CEA responses. The purpose of the current study was to treat patients with surgically resected colon cancer with CeaVac to determine the immune response and clinical outcome to treatment with vaccine. We also compared the immune responses between patients treated with fluorouracil (5-FU) chemotherapy regimens plus vaccine versus vaccine alone.

PATIENTS AND METHODS

Thirty-two patients with resected Dukes' B, C, and D, and incompletely resected Dukes' D disease were treated with 2 mg of CeaVac every other week for four injections and then monthly until tumor recurrence or progression. Fourteen patients were treated concurrently with 5-FU chemotherapy regimens.

RESULTS

All 32 patients entered onto this trial generated high-titer immunoglobulin G and T-cell proliferative immune responses against CEA. The 5-FU regimens did not have a qualitative or quantitative effect on the immune response. Three of 15 patients with Dukes' B and C disease progressed at 19, 24, and 35 months. Seven of eight patients with completely resected Dukes' D disease remained on study from 12 to 33 months; one patient with resected Dukes' D disease relapsed at 9 months. One patient with incompletely resected Dukes' D disease remained on study at 14 months without evidence of progression; eight experienced disease progression at 6 to 31 months.

CONCLUSION

CeaVac consistently generated a potent anti-CEA humoral and cellular immune response in all 32 patients entered onto this trial. A number of very high-risk patients continue on study. 5-FU regimens, which are the standard of care for patients with Dukes' C disease, did not affect the immune response. These data warrant a phase III trial for patients with resected colon cancer.

Variation at 4 short tandem repeat loci in 8 population groups of India

We have determined the nature and extent of variation at 4 STR loci (CSF1P0, TPOX, TH01, VWA) in 8 caste and tribal population groups of eastern and northern India. Large differences in allele frequencies among the groups were found. Average heterozygosities in all populations were high (approximately 80%). The overall extent of gene differentiation among the 8 groups was high (GST = 0.04). The nature of genomic affinities based on these 4 STR loci does not completely agree with our earlier finding based on classical genetic markers that geographic proximity of habitat has a greater influence on genetic similarity between populations than sociocultural proximity does.

Human-specific insertion/deletion polymorphisms in Indian populations and their possible evolutionary implications

DNA samples from 396 unrelated individuals belonging to 14 ethnic populations of India, inhabiting various geographical locations and occupying various positions in the socio-cultural hierarchy, were analysed in respect of 8 human-specific polymorphic insertion/deletion loci. All loci, except Alu CD4, were found to be highly polymorphic in all populations. The levels of average heterozygosities were found to be very high in all populations and, in most populations, also higher than those predicted by the island model of population structure. The coefficient of gene differentiation among Indian populations was found to be higher than populations in most other global regions, except Africa. These results are discussed in the light of two possible scenarios of evolution of Indian populations in the broader context of human evolution.

Antibody responses in melanoma patients immunized with an anti-idiotype antibody mimicking disialoganglioside GD2

We initiated a clinical trial for patients with advanced malignant melanoma treated with an anti-idiotype antibody that mimics the disialoganglioside GD2. We report the clinical and immune responses of the first 12 patients entered into this trial. Patients received 1-, 2-, 4-, or 8-mg doses of the anti-idiotype antibody mixed with 100 microg of QS-21 adjuvant every other week, four times, and then monthly. Twelve patients have been on trial for 2-23 months, and all of them have generated immune responses. Patients were removed from the study if they demonstrated disease progression. Hyperimmune sera from all 12 patients revealed an anti-anti-idiotypic Ab3 response, as demonstrated by the inhibition of Ab2 binding to Ab1 by patients' immune sera. To further test the anti-anti-idiotypic response, patients' Ab3 antibodies were affinity purified on Sepharose 4B columns containing adsorbed immunizing anti-idiotype immunoglobulin. Purified Ab3 of all patients studied inhibited binding of Ab1 to a GD2-positive cell line. Purified Ab3 also inhibited binding of Ab1 to purified GD2, in a manner comparable to equal quantities of purified Ab1. The patient Ab3 was truly an Ab1' because it specifically bound to purified disialoganglioside GD2. The isotypic specificity of the Ab3 antibody was predominantly IgG, with only minimal IgM. The predominant IgG subclass was IgG1, with approximately equal quantities of IgG2, IgG3, and IgG4. These Ab3 antibodies reacted specifically with tumor cells expressing GD2 by immune flow cytometry and immunoperoxidase assays. Five patients' Ab3 antibodies studied for antibody-dependent cellular cytotoxicity were positive. One patient had a complete clinical response, with resolution of soft tissue disease, and six patients had stable disease, ranging from 9 to 23 months, and are being continued on vaccine therapy. Toxicity consisted of local reaction at the site of the injection, including induration and pain that generally resolved within a few days. Mild fever and chills were observed in 75% of the patients but rarely required acetaminophen. There was no additional toxicity, including abdominal pain that was previously seen with infusion of murine monoclonal anti-GD2 antibody. Current trials include patients with stage III melanoma and small cell lung cancer. Future trials will attempt to enhance the antitumor response by the addition of interleukin 2, granulocyte macrophage colony-stimulating factor, and other cytokines, together with the 1A7 vaccine.

Molecular mimicry of carcinoembryonic antigen by peptides derived from the structure of an anti-idiotype antibody

Our goal was to use carcinoembryonic antigen (CEA) as a target for immunotherapy in CEA-positive cancer patients who are all immune tolerant to the native antigen. We isolated and characterized an anti-idiotype monoclonal antibody 3H1, which mimics a distinct and specific epitope of the Mr 180,000 CEA and can be used as a surrogate for CEA. In Phase Ib clinical trials in a group of 23 advanced colorectal cancer patients, 3H1 induced both humoral and cellular anti-3H1 responses, as well as anti-CEA immunity. To study the cellular immunity invoked by 3H1 at the molecular level, we have cloned and sequenced the cDNAs encoding the variable heavy and light chains of 3H1 and deduced the amino acid sequences of the encoded proteins. To identify any cross-reactive peptides of 3H1 and CEA, we compared the amino acid sequences of 3H1 with those of CEA and found several regions of homology in 3H1 heavy and light chain variable domains, as well as in the framework regions. To search for potential cross-reactive T-cell epitopes, a number of peptides were synthesized based on 3H1/CEA homology and were used as stimulants in cell proliferation assays, using peripheral blood mononuclear cells from a group of 3H1-immunized CEA-positive cancer patients in the adjuvant setting. Two partially homologous peptides, designated LCD-2 (from 3H1) and CEA-B (from CEA), were identified in 10 of 21 adjuvant patients by strong proliferation responses (stimulation index, 3-50-fold), which were extensively studied in five of these individuals over an extended period of time (12-24 months). We saw no correlation with the MHC class I haplotype of the patients. Analysis of the subtype of the responding T cells demonstrated that primarily CD4+ T cells were stimulated by both 3H1 and 3H1-derived peptides. Interleukin 2, interleukin 4, and IFN-gamma were assayed in the culture medium of peripheral blood mononuclear cells stimulated with 3H1, CEA, and LCD-2 to determine the T-cell helper subset induced by these stimulants. The in vitro responses were mainly associated with secretion of IFN-gamma, which suggested that the induced T cells were most likely CD4+ Th1 type. Future studies will include the design of second-generation LCD-2 and CEA peptides to further enhance antigenicity, to characterize the responding T-cell populations more fully, and to test refined peptides for immunogenicity.

Frequency of homozygous null mutation at the glutathione-s-transferase M1 locus in some populations of Orissa, India

GSTM1, one of the mu type glutathione-s-transferase isozymes in human, has been observed to be inherited dominantly, and the polymorphism of this gene can be detected by polymerase chain reaction (PCR). In this report we have determined the frequency of a homozygous deletion mutation of the GSTM1 gene in some populations of the Sundergarh District in Orissa, India. About 24% of unrelated individuals (n = 72) were detected to carry this deletion mutation in homozygous form. Possible implications of this homozygous deletion are discussed.

Induction of IgG antibodies by an anti-idiotype antibody mimicking disialoganglioside GD2

The anti-idiotype (Id) monoclonal antibody (mAb) 1A7 immunoglobulin G1 (IgG1, kappa), raised in syngeneic mice against the murine anti-ganglioside GD2 mAb 14G2a mimics a carbohydrate epitope on GD2 and serves as a surrogate protein antigen for this disialoganglioside. Immunization of allogeneic C57BL/6 mice and rabbits with 1A7 induced anti-GD2 antibodies of IgG isotype that recognize purified GD2 by enzyme-linked immunosorbent assay (ELISA) and GD2-positive human melanoma cells (M21/P6) by fluorescence-activated cell sorter (FACS) analysis. The specificity of the antisera for GD2 was further confirmed by dot-blot analysis. These antisera also specifically lyse GD2-positive M21/P6 target cells in an antibody-dependent cellular cytotoxicity assay. Taken together, these results suggest that the anti-Id 1A7 can induce GD2-specific IgG antibodies that can recognize cell surface-associated as well as soluble disialoganglioside GD2.