Activation of intestinal immunity by pathogen effector-triggered aggregation of lysosomal TIR-1/SARM1

TIR-domain proteins with enzymatic activity are essential for immunity in plants, animals, and bacteria. However, it is not known how these proteins function in pathogen sensing in animals. We discovered that a TIR-domain protein (TIR-1/SARM1) is strategically expressed on the membranes of a lysosomal sub-compartment, which enables intestinal epithelial cells in the nematode C. elegans to survey for pathogen effector-triggered host damage. We showed that a redox active virulence effector secreted by the bacterial pathogen Pseudomonas aeruginosa alkalinized and condensed a specific subset of lysosomes by inducing intracellular oxidative stress. Concentration of TIR-1/SARM1 on the surface of these organelles triggered its multimerization, which engages its intrinsic NADase activity, to activate the p38 innate immune pathway and protect the host against microbial intoxication. Thus, lysosomal TIR-1/SARM1 is a sensor for oxidative stress induced by pathogenic bacteria to activate metazoan intestinal immunity.

Transcriptional suppression of sphingolipid catabolism controls pathogen resistance in C. elegans

Sphingolipids are required for diverse biological functions and are degraded by specific catabolic enzymes. However, the mechanisms that regulate sphingolipid catabolism are not known. Here we characterize a transcriptional axis that regulates sphingolipid breakdown to control resistance against bacterial infection. From an RNAi screen for transcriptional regulators of pathogen resistance in the nematode C. elegans, we identified the nuclear hormone receptor nhr-66, a ligand-gated transcription factor homologous to human hepatocyte nuclear factor 4. Tandem chromatin immunoprecipitation-sequencing and RNA sequencing experiments revealed that NHR-66 is a transcriptional repressor, which directly targets sphingolipid catabolism genes. Transcriptional de-repression of two sphingolipid catabolic enzymes in nhr-66 loss-of-function mutants drives the breakdown of sphingolipids, which enhances host susceptibility to infection with the bacterial pathogen Pseudomonas aeruginosa. These data define transcriptional control of sphingolipid catabolism in the regulation of cellular sphingolipids, a process that is necessary for pathogen resistance.

A C. elegans neuron both promotes and suppresses motor behavior to fine tune motor output

How neural circuits drive behavior is a central question in neuroscience. Proper execution of motor behavior requires precise coordination of many neurons. Within a motor circuit, individual neurons tend to play discrete roles by promoting or suppressing motor output. How exactly neurons function in specific roles to fine tune motor output is not well understood. In C. elegans, the interneuron RIM plays important yet complex roles in locomotion behavior. Here, we show that RIM both promotes and suppresses distinct features of locomotion behavior to fine tune motor output. This dual function is achieved via the excitation and inhibition of the same motor circuit by electrical and chemical neurotransmission, respectively. Additionally, this bi-directional regulation contributes to motor adaptation in animals placed in novel environments. Our findings reveal that individual neurons within a neural circuit may act in opposing ways to regulate circuit dynamics to fine tune behavioral output.

Non-canonical pattern recognition of a pathogen-derived metabolite by a nuclear hormone receptor identifies virulent bacteria in C. elegans

Distinguishing infectious pathogens from harmless microorganisms is essential for animal health. The mechanisms used to identify infectious microbes are not fully understood, particularly in metazoan hosts that eat bacteria as their food source. Here, we characterized a non-canonical pattern-recognition system in Caenorhabditis elegans (C. elegans) that assesses the relative threat of virulent Pseudomonas aeruginosa (P. aeruginosa) to activate innate immunity. We discovered that the innate immune response in C. elegans was triggered by phenazine-1-carboxamide (PCN), a toxic metabolite produced by pathogenic strains of P. aeruginosa. We identified the nuclear hormone receptor NHR-86/HNF4 as the PCN sensor in C. elegans and validated that PCN bound to the ligand-binding domain of NHR-86/HNF4. Activation of NHR-86/HNF4 by PCN directly engaged a transcriptional program in intestinal epithelial cells that protected against P. aeruginosa. Thus, a bacterial metabolite is a pattern of pathogenesis surveilled by nematodes to identify a pathogen in its bacterial diet.

NHR-49/PPAR-α and HLH-30/TFEB cooperate for C. elegans host defense via a flavin-containing monooxygenase

The model organism Caenorhabditis elegans mounts transcriptional defense responses against intestinal bacterial infections that elicit overlapping starvation and infection responses, the regulation of which is not well understood. Direct comparison of C. elegans that were starved or infected with Staphylococcus aureus revealed a large infection-specific transcriptional signature, which was almost completely abrogated by deletion of transcription factor hlh-30/TFEB, except for six genes including a flavin-containing monooxygenase (FMO) gene, fmo-2/FMO5. Deletion of fmo-2/FMO5 severely compromised infection survival, thus identifying the first FMO with innate immunity functions in animals. Moreover, fmo-2/FMO5 induction required the nuclear hormone receptor, NHR-49/PPAR-α, which controlled host defense cell non-autonomously. These findings reveal an infection-specific host response to S. aureus, identify HLH-30/TFEB as its main regulator, reveal FMOs as important innate immunity effectors in animals, and identify the mechanism of FMO regulation through NHR-49/PPAR-α during S. aureus infection, with implications for host defense and inflammation in higher organisms.

Transcription factors NHR-49/PPARα and HLH-30/TFEB promote host defense in C. elegans via a flavin-containing monooxygenase

During bacterial infection, the host is confronted with multiple overlapping signals that are integrated at the organismal level to produce defensive host responses. How multiple infection signals are sensed by the host and how they elicit the transcription of host defense genes is much less understood at the whole-animal level than at the cellular level. The model organism Caenorhabditis elegans is known to mount transcriptional defense responses against intestinal bacterial infections that elicit overlapping starvation and infection responses, but the regulation of such responses is not well understood. Direct comparison of C. elegans that were starved or infected with Staphylococcus aureus revealed a large infection-specific transcriptional signature. This signature was almost completely abrogated by the deletion of transcription factor hlh-30/TFEB, except for six genes including a flavin-containing monooxygenase (FMO) gene, fmo-2/FMO5. Deletion of fmo-2/FMO5 severely compromised infection survival, thus identifying the first FMO with innate immunity functions in animals. Further, fmo-2/FMO5 was specifically induced by Gram-positive pathogens and Gram-positive natural microbiota of C. elegans. Moreover, the mechanism of fmo-2/FMO5 induction required the nuclear receptor, NHR-49/PPARα, which induced fmo-2/FMO5 and host defense cell non-autonomously. These findings for the first time reveal an infection-specific host response to S. aureus, identify HLH-30/TFEB as its main regulator, reveal that FMOs are important innate immunity effectors in animals, and identify the mechanism of FMO regulation through NHR-49/PPARα in C. elegans, with important implications for innate host defense in higher organisms.

Nervous system control of intestinal host defense in C. elegans

Interplay between the nervous and immune systems is critical for homeostasis, and its dysfunction underlies pathologies such as multiple sclerosis, autism, leukemia, and inflammation. The nematode Caenorhabditis elegans provides an opportunity to define evolutionarily conserved mechanisms of regulation of host innate immunity and inflammation in a genetically tractable whole-animal system. In the past few years, the C. elegans nervous system has emerged as an integral part of host defense against pathogens, acting through diverse mechanisms to repress or induce protective transcriptional responses to infection in distal tissues. In this review, we discuss current knowledge of the mechanisms through which the C. elegans nervous system controls the expression of host defense genes in the intestinal epithelium. Although still incomplete, the insights derived from such work have broad implications for neural regulation of epithelial function at mucosal barriers in higher organisms in health and disease.

A Nutrition-Longevity Tradeoff Enforced by Innate Immunity

Dietary restriction (DR) extends lifespan in multiple animal species, but the underlying molecular mechanisms remain poorly understood. A recent study published in Cell Metabolism by Wu et al. (2019) shows that DR represses an evolutionarily conserved p38 MAPK pathway involved in innate immunity, leading to diminished expression of p38 MAPK-regulated genes and extended lifespan.

Intestinal Epithelial Wnt Signaling Mediates Acetylcholine-Triggered Host Defense against Infection

Regulated antimicrobial peptide expression in the intestinal epithelium is key to defense against infection and to microbiota homeostasis. Understanding the mechanisms that regulate such expression is necessary for understanding immune homeostasis and inflammatory disease and for developing safe and effective therapies. We used Caenorhabditis elegans in a preclinical approach to discover mechanisms of antimicrobial gene expression control in the intestinal epithelium. We found an unexpected role for the cholinergic nervous system. Infection-induced acetylcholine release from neurons stimulated muscarinic signaling in the epithelium, driving downstream induction of Wnt expression in the same tissue. Wnt induction activated the epithelial canonical Wnt pathway, resulting in the expression of C-type lectin and lysozyme genes that enhanced host defense. Furthermore, the muscarinic and Wnt pathways are linked by conserved transcription factors. These results reveal a tight connection between the nervous system and the intestinal epithelium, with important implications for host defense, immune homeostasis, and cancer.

Promoter methylation and gene polymorphism are two independent events in regulation of GSTP1 gene expression

Breast carcinogenesis is a multistep process, involving both genetic and epigenetic modification process of genes, involved in diverse pathways ranging from DNA repair to metabolic processes. This study was undertaken to assess the role of promoter methylation of GSTP1 gene, a member of glutathione-S-transferase family of enzymes, in relation to its expression, polymorphism, and clinicopathological parameters. Tissue samples were taken from breast cancer patients and paired with their normal adjacent tissues. A total of 51 subjects were studied, in which the frequency of promoter methylation in cancerous tissue was 37.25% as against 11% in the normal tissues ( p ≤ 0.001). The hypermethylated status of the gene was significantly associated with the loss of the protein expression ( r = −0.449, p = 0.001, odds ratio = 7.42, 95% confidence interval = 2.05–26.92). Furthermore, when compared with the clinical parameters, the significant association was found between the promoter hypermethylation and lymph node metastasis ( p ≤ 0.001), tumor stage ( p = 0.039), tumor grade ( p = 0.028), estrogen receptor status ( p = 0.018), and progesterone receptor status ( p = 0.046). Our study is the first of its kind in Kashmiri population, which indicates that GSTP1 shows aberrant methylation pattern in the breast cancer with the consequent loss in the protein expression. Furthermore, it also shows that the gene polymorphism (Ile105Val) at codon 105 is not related to the promoter methylation and two are the independent events in breast cancer development.

Past experience resets behavior: CaMK takes the heat

How past experiences reshape behavior is not well understood. In this issue, two studies (Schild et al., 2014; Yu et al., 2014) dissected the molecular mechanisms underlying experience-dependent plasticity in thermosensory behavior. They show that Ca(2+)/calmodulin-dependent kinase I (CaMKI) regulates thermal preferences according to past experience.

Epigenetic silencing of TSHR gene in thyroid cancer patients in relation to their BRAF V600E mutation status

Promoter hypermethylation of multiple genes have been identified to play a role in thyroid cancers and most prominent among them is TSHR gene promoter hypermethylation in particular showing a close association with BRAF gene-altered status. Thus, the aim of this study was to analyze the TSHR gene promoter hypermethylation in a series of thyroid tumor tissues in the backdrop of their BRAF gene mutational status. Methylation-specific PCR (MS-PCR) was used for detection of promoter methylation while BRAF gene mutational status was analyzed by PCR followed by DNA sequencing in the same series of 60 thyroid tumor tissues. The promoter region of TSHR gene was found to be methylated in 25 % (15 of 60) of the thyroid cancer patients. Patients having elevated TSH levels showed strong association with methylation (OR = 4.0, P = 0.02). BRAF V600E mutation was found in 25 % (15 of 60) patients and among them TSHR promoter was methylated in 73.3 % (11 of 15) patients and only 26.7 % (4 of 15) patients with mutated BRAF showed the absence of TSHR promoter methylation. We found a significant association between the presence of methylation in TSHR with the BRAF V600E mutation-positive cases (P < 0.05). In conclusion, our study showed a high implication of TSHR gene methylation and its significant association with BRAF V600E mutation in thyroid tumors, depicting a positive connection between TSHR pathway and MAP Kinase pathway.

Impact of molecular alterations of BRAF in the pathogenesis of thyroid cancer

BRAF alterations represent a novel indicator of the progression and aggressiveness of thyroid carcinogenesis. So, the main aim of the study was to elucidate the involvement of BRAF gene mutations and its expression in Kashmiri (North India) patients and investigate their association with clinico-pathological characteristics. Mutational analysis of BRAF gene was performed by polymerase chain reaction followed by DNA sequencing, whereas analysis of BRAF protein expression was done by western blotting. Overall mutations in BRAF was found to be 25% (15 of 60) and all of them were transversions (T>A) affecting codon 600 (valine to glutamine), restricted only to papillary thyroid cancer and well-differentiated grade. Patients with well-differentiated disease and in particular elevated thyroid-stimulating hormone levels were significantly associated with BRAF mutations (P < 0.05). Overall, 90% (54 of 60) of thyroid cancer cases showed increased expression of BRAF and non-smokers being significantly associated with BRAF over-expression. Totally, 86.7% (13 of 15) of BRAF mutation-positive patients were having over-expression of BRAF protein, whereas 91.2% (41 of 45) of patients with wild-type BRAF status were having over-expressed BRAF protein (P > 0.05). We conclude that both mutational events as well as over-expression of BRAF gene is highly implicated in pathogenesis of thyroid cancer and the BRAF protein over-expression is independent of the BRAF mutational status of thyroid cancer patients.

Association between p16, hMLH1 and E-cadherin promoter hypermethylation and intake of local hot salted tea and sun-dried foods in Kashmiris with gastric tumors

The aim of this study was to evaluate the methylation status of three important cancer related genes viz. p16, E-cadherin and hMLH1 promoters and to associate the findings with specific dietary habits in Kashmiris, a culturally distinct population in India, with gastric cancer. The study subjects were divided into three age groups viz. 0-30 yrs (1st), 31-60 yrs (2nd) and 61-90 yrs (3rd). A highly significant association between the intake of local hot salted tea in 2nd (p=0.001) and 3rd (p=0.009) age groups was observed with the promoter hypermethylation of E cadherin. Again a highly significant association between the aberrant methylation of hMLH1 (p=0.000) and p16 (p=0.000) promoters and the intake of local hot salted tea was observed in the 2nd age group of gastric cancer patients. The intake of sun-dried food was also significantly associated with the promoter hypermethylation of E cadherin (p=0.003) and p16 (p=0.015) genes in 3rd age group. The results of the present study suggest a close association between the aberrant methylation of p16, E-cadherin and hMLH1 promoters and the intake of local hot salted tea and sun-dried foods in Kashmiri population.

D1 dopamine receptor signaling is modulated by the R7 RGS protein EAT-16 and the R7 binding protein RSBP-1 in Caenoerhabditis elegans motor neurons

Dopamine signaling modulates voluntary movement and reward-driven behaviors by acting through G protein-coupled receptors in striatal neurons, and defects in dopamine signaling underlie Parkinson's disease and drug addiction. Despite the importance of understanding how dopamine modifies the activity of striatal neurons to control basal ganglia output, the molecular mechanisms that control dopamine signaling remain largely unclear. Dopamine signaling also controls locomotion behavior in Caenorhabditis elegans. To better understand how dopamine acts in the brain we performed a large-scale dsRNA interference screen in C. elegans for genes required for endogenous dopamine signaling and identified six genes (eat-16, rsbp-1, unc-43, flp-1, grk-1, and cat-1) required for dopamine-mediated behavior. We then used a combination of mutant analysis and cell-specific transgenic rescue experiments to investigate the functional interaction between the proteins encoded by two of these genes, eat-16 and rsbp-1, within single cell types and to examine their role in the modulation of dopamine receptor signaling. We found that EAT-16 and RSBP-1 act together to modulate dopamine signaling and that while they are coexpressed with both D1-like and D2-like dopamine receptors, they do not modulate D2 receptor signaling. Instead, EAT-16 and RSBP-1 act together to selectively inhibit D1 dopamine receptor signaling in cholinergic motor neurons to modulate locomotion behavior.

Secondary tuberculosis of breast: case report

Tuberculosis of breast is a rare disease which is difficult to differentiate from carcinoma of breast. The involvement of breast can be primary or secondary to some focus in body. A case of secondary tuberculosis of right breast in a 21-year-old female from Kashmir, India, is being reported. Presentation was as a painless discharging sinus of right breast. A tubercular foci of rib was the affecting source of disease. No other evidence of tuberculosis was present in the body. Resection of involved rib segment, along with the discharging sinus, was performed. The patient had antitubercular therapy for 9 months, with no recurrence seen in followup.

Peritoneal hydatidosis in a young girl

We report a case of peritoneal hydatidosis that occurred post laparotomy. Patient was diagnosed nine months after she had laparotomy for suspected acute appendicitis. The whole peritoneal cavity was studded with cysts. In view of diffuse involvement, patient was managed conservatively and showed response to medical therapy.

Molecular gate keepers succumb to gene aberrations in colorectal cancer in Kashmiri population, revealing a high incidence area

BACKGROUND/AIM

Colorectal cancer (CRC) is one of the leading malignancies worldwide and has been reported to show geographical variation in its incidence, even within areas of ethnic homogeneity. The aim of this study was to identify p53 and K-ras gene mutations in CRC patients in a Kashmiri population, and to assess whether these mutations are linked with clinicopathological parameters.

MATERIALS AND METHODS

Paired tumor and normal tissue samples from a consecutive series of 53 patients undergoing resective surgery for CRC were prospectively studied for p53 and K-ras gene mutations by PCR/single strand conformation polymorphism (SSCP).

RESULTS

Less than half (45%, 19/42) of the patients presented mutations in the p53 gene. Twenty eight mutations were found in the p53 gene, which comprised of 23 substitutions (17 transitions + 6 transversions), and five insertions. The 23 substitutions constituted 18 missense mutations, two nonsense mutations, and three silent mutations. Of the 28 mutations (7.14%) observed in this study, 2 were not previously reported for CRC samples and were identified as novel p53 mutations. A few patients (22.64%, 12/53) presented with mutations in K-ras, constituting 13 missense mutations, out of which 11 were G-->A transitions, one was a G-->C transversion, and one a G-->T transversion. More than half (61.5%) of the mutations occurred in codon 12 whereas a few (38.5%) occurred in codon 13. One tumor contained missense mutations in both codons. Comparison of the mutation profiles of our patients with those of other ethnic populations and regions reflected both differences and similarities, indicating co-exposure to a unique set of risk factors.

CONCLUSION

Mutations of the p53 and K-ras genes are some of the most common genetic changes in the development of human CRC. The high frequency of p53 gene mutations implicates p53 as a predominant factor for CRC in the high-risk ethnic Kashmiri population.

Extended spectrum B-lactamase mediated resistance in Escherichia coli in a tertiary care hospital

BACKGROUND

ESBL occur mostly in Enterobacteriaceae e.g. Escherichia coli. ESBLs are clinically important because they destroy cephalosporin's, work horse hospital antibiotics, given as first line agents to many severely ill patients. Delayed recognition and inappropriate treatment of severe infections caused by ESBL producers with cephalosporin has been associated with increased mortality. ESBL-mediated resistance is not always obvious in vitro to all cephalosporin. Many ESBL producers are multi -resistant to non-B-Lactam antibiotics such as quinolones and amino glycosides, narrowing treatment options. Some producers achieve outbreak status spreading among patients and locals, perhaps owing to particular pathogenicity traits.

METHODS

A total of 221 Escherichia coli isolates from different clinical specimens during the period of August 2005 to July 2007, were screened for potential ESBL activity. These strains were isolated from different clinical specimens like urine, blood, sputum, pus and other body fluids which were received in the bacteriological division of microbiology.

RESULTS

Two hundred and twenty one Escherichia coli isolates were isolated from different clinical specimens like urine, blood, sputum, pus and other body fluids submitted for both in and out-patients of the hospital during the period August2005 to July2007. All of them were subjected to screening by using ceftazidime, cefotaxime or ceftriaxone. Two hundred and eleven were positive for potential ESBL producers out of 221. 95.4%of E. coli (211/221) were screen positive which were subjected to confirmatory tests

CONCLUSION

Maximum number of ESBLs was from in-patients followed by out-patients. The out-patient presence of ESBL is of main concern as it is now come to the alert of the physician that ESBL is spreading fast in the community and responsible for community-acquired ESBLs and maximum number being from urine specimen.

Haemosuccus pancreaticus: a clinical challenge

BACKGROUND

Haemosuccus pancreaticus is a rare complication of pancreatitis. It is a diagnostic problem for even the most astute clinician and a challenge for the expert endoscopist. We report a 25-year-old male patient who had all the features usually seen in haemosuccus pancreaticus patients: recurrent obscure upper gastrointestinal bleeding, pancreatitis, pseudocyst formation, ductal disruption, fistula and pancreatic ascites. The patient was treated by subtotal pancreatectomy, splenectomy and drainage of the pseudocyst. Although pancreatic duct communication with the surrounding vasculature could not be ascertained, we strongly believe the patient had haemosuccus pancreaticus because, over a follow-up period of 3 years, the patient was not only ascites free, but did not experience any further upper gastrointestinal bleeding. We believe that in evaluating patients with recurrent obscure gastrointestinal bleeding, one should always remember that the pancreas is a part of the gastrointestinal tract and, like other organs, is prone to blood loss.

The ideal treatment of the typhoid enteric perforation - resection anastomosis

Eighty-one cases of typhoid enteric perforation were studied prospectively after separating them into four groups. Group A patients were treated with resection anastomosis, group B by debridement of margins of the perforation/wedge excision and simple closure, group C by simple closure and group D by ileostomy of perforated ileum or simple peritoneal drainage. A copious lavage of the peritoneal cavity with normal saline was performed in all four groups. The complication and mortality rates for group A patients were 37.50% and 21.47%, respectively, very much less than that observed in the other three groups. The ideal treatment for typhoid enteric perforation was found to be resection-anastomosis with copious peritoneal lavage.