A diet of oxidative stress-adapted bacteria improves stress resistance and lifespan in C. elegans via p38-MAPK

Organisms across taxa face stresses including variable temperature, redox imbalance, and xenobiotics. Successfully responding to stress and restoring homeostasis are crucial for survival. Aging is associated with a decreased stress response and alterations in the microbiome, which contribute to disease development. Animals and their microbiota share their environment; however, microbes have short generation time and can rapidly evolve and potentially affect host physiology during stress. Here, we leverage Caenorhabditis elegans and its simplified bacterial diet to demonstrate how microbial adaptation to oxidative stress affects the host's lifespan and stress response. We find that worms fed stress-evolved bacteria exhibit enhanced stress resistance and an extended lifespan. Through comprehensive genetic and metabolic analysis, we find that iron in stress-evolved bacteria enhances worm stress resistance and lifespan via activation of the mitogen-activated protein kinase pathway. In conclusion, our study provides evidence that understanding microbial stress-mediated adaptations could be used to slow aging and alleviate age-related health decline.

Dietary Iron Is Necessary to Support Proliferative Regeneration after Intestinal Injury

BACKGROUND

Tissue repair and regeneration in the gastrointestinal system are crucial for maintaining homeostasis, with the process relying on intricate cellular interactions and affected by micro- and macro-nutrients. Iron, essential for various biological functions, plays a dual role in tissue healing by potentially causing oxidative damage and participating in anti-inflammatory mechanisms, underscoring its complex relationship with inflammation and tissue repair.

OBJECTIVE

The study aimed to elucidate the role of low dietary iron in gastrointestinal tissue repair.

METHODS

We utilized quantitative iron measurements to assess iron levels in inflamed regions of patients with ulcerative colitis and Crohn's disease. In addition, 3 mouse models of gastrointestinal injury/repair (dextran sulfate sodium-induced colitis, radiation injury, and wound biopsy) were used to assess the effects of low dietary iron on tissue repair.

RESULTS

We found that levels of iron in inflamed regions of both patients with ulcerative colitis and Crohn's disease are elevated. Similarly, during gastrointestinal repair, iron levels were found to be heightened, specifically in intestinal epithelial cells across the 3 injury/repair models. Mice on a low-iron diet showed compromised tissue repair with reduced proliferation. In standard diet, epithelial cells and the stem cell compartment maintain adequate iron stores. However, during a period of iron deficiency, epithelial cells exhaust their iron reserves, whereas the stem cell compartments maintain their iron pools. During injury, when the stem compartment is disrupted, low iron levels impair proliferation and compromise repair mechanisms.

CONCLUSIONS

Low dietary iron impairs intestinal repair through compromising the ability of epithelial cells to aid in intestinal proliferation.

Recharacterization of RSL3 reveals that the selenoproteome is a druggable target in colorectal cancer

Ferroptosis is an iron-dependent, non-apoptotic form of cell death resulting from the accumulation of lipid peroxides. Colorectal cancer (CRC) accumulates high levels of intracellular iron and reactive oxygen species (ROS), thereby sensitizing cells to ferroptosis. The selenoprotein glutathione peroxidase (GPx4) is a key enzyme in the detoxification of lipid peroxides and can be inhibited by the compound (S)-RSL3 ([1S,3R]-RSL3). However, the stereoisomer (R)-RSL3 ([1R,3R]-RSL3), which does not inhibit GPx4, exhibits equipotent activity to (S)-RSL3 across a panel of CRC cell lines. Utilizing CRC cell lines with an inducible knockdown of GPx4, we demonstrate that (S)-RSL3 sensitivity does not align with GPx4 dependency. Subsequently, a biotinylated (S)-RSL3 was then synthesized to perform affinity purification-mass spectrometry (AP-MS), revealing that (S)-RSL3 acts as a pan-inhibitor of the selenoproteome, targeting both the glutathione and thioredoxin peroxidase systems as well as multiple additional selenoproteins. To investigate the therapeutic potential of broadly disrupting the selenoproteome as a therapeutic strategy in CRC, we employed further chemical and genetic approaches to disrupt selenoprotein function. The findings demonstrate that the selenoprotein inhibitor Auranofin can induce ferroptosis and/or oxidative cell death both in-vitro and in-vivo. Consistent with this data we observe that AlkBH8, a tRNA-selenocysteine methyltransferase required for the translational incorporation of selenocysteine, is essential for CRC growth. In summary, our research elucidates the complex mechanisms underlying ferroptosis in CRC and reveals that modulation of the selenoproteome provides multiple new therapeutic targets and opportunities in CRC.

Activation of Intestinal HIF2α Ameliorates Iron-Refractory Anemia

In clinics, hepcidin levels are elevated in various anemia-related conditions, particularly in iron-refractory anemia and in high inflammatory states that suppress iron absorption, which remains an urgent unmet medical need. To identify effective treatment options for various types of iron-refractory anemia, the potential effect of hypoxia and pharmacologically-mimetic drug FG-4592 (Roxadustat) are evaluated, a hypoxia-inducible factor (HIF)-prolyl hydroxylase (PHD) inhibitor, on mouse models of iron-refractory iron-deficiency anemia (IRIDA), anemia of inflammation and 5-fluorouracil-induced chemotherapy-related anemia. The potent protective effects of both hypoxia and FG-4592 on IRIDA as well as other 2 tested mouse cohorts are found. Mechanistically, it is demonstrated that hypoxia or FG-4592 could stabilize duodenal Hif2α, leading to the activation of Fpn transcription regardless of hepcidin levels, which in turn results in increased intestinal iron absorption and the amelioration of hepcidin-activated anemias. Moreover, duodenal Hif2α overexpression fully rescues phenotypes of Tmprss6 knockout mice, and Hif2α knockout in the gut significantly delays the recovery from 5-fluorouracil-induced anemia, which can not be rescued by FG-4592 treatment. Taken together, the findings of this study provide compelling evidence that targeting intestinal hypoxia-related pathways can serve as a potential therapeutic strategy for treating a broad spectrum of anemia, especially iron refractory anemia.

Renal-specific loss of ferroportin disrupts iron homeostasis and attenuates recovery from acute kidney injury

Chronic kidney disease is increasing at an alarming rate and correlates with the increase in diabetes, obesity, and hypertension that disproportionately impact socioeconomically disadvantaged communities. Iron plays essential roles in many biological processes including oxygen transport, mitochondrial function, cell proliferation, and regeneration. However, excess iron induces the generation and propagation of reactive oxygen species, which lead to oxidative stress, cellular damage, and ferroptosis. Iron homeostasis is regulated in part by the kidney through iron resorption from the glomerular filtrate and exports into the plasma by ferroportin (FPN). Yet, the impact of iron overload in the kidney has not been addressed. To test more directly whether excess iron accumulation is toxic to kidneys, we generated a kidney proximal tubule-specific knockout of FPN. Despite significant intracellular iron accumulation in FPN mutant tubules, basal kidney function was not measurably different from wild type kidneys. However, upon induction of acute kidney injury (AKI), FPN mutant kidneys exhibited significantly more damage and failed recovery, evidence for ferroptosis, and increased fibrosis. Thus, disruption of iron export in proximal tubules, leading to iron overload, can significantly impair recovery from AKI and can contribute to progressive renal damage indicative of chronic kidney disease. Understanding the mechanisms that regulate iron homeostasis in the kidney may provide new therapeutic strategies for progressive kidney disease and other ferroptosis-associated disorders.NEW & NOTEWORTHY Physiological iron homeostasis depends in part on renal resorption and export into the plasma. We show that specific deletion of iron exporters in the proximal tubules sensitizes cells to injury and inhibits recovery. This can promote a chronic kidney disease phenotype. Our paper demonstrates the need for iron balance in the proximal tubules to maintain and promote healthy recovery after acute kidney injury.

Myeloid Hif2α is not essential to maintain systemic iron homeostasis

Dietary consumption serves as the primary source of iron uptake, and erythropoiesis acts as a major regulator of systemic iron demand. In addition to intestinal iron absorption, macrophages play a crucial role in recycling iron from senescent red blood cells. The kidneys are responsible for the production of erythropoietin (Epo), which stimulates erythropoiesis, whereas the liver plays a central role in producing the iron-regulatory hormone hepcidin. The transcriptional regulator hypoxia-inducible factor (HIF)2α has a central role in the regulation of Epo, hepcidin, and intestinal iron absorption and therefore plays a crucial role in coordinating the tissue crosstalk to maintain systemic iron demands. However, the precise involvement of Hif2α in macrophages in terms of iron homeostasis remains uncertain. Our study demonstrates that deleting Hif2α in macrophages does not disrupt the expression of iron transporters or basal erythropoiesis. Mice lacking Hif2α in myeloid cells exhibited no discernible differences in hemodynamic parameters, including hemoglobin concentrations and erythrocyte count, when compared with littermate controls. This similarity was observed under conditions of both dietary iron deficiency and acute erythropoietic demand. Notably, we observed a significant increase in the expression of iron transporters in the duodenum during iron deficiency, indicating heightened iron absorption. Therefore, our findings suggest that the disruption of Hif2α in myeloid cells does not significantly impact systemic iron homeostasis under normal physiologic conditions. However, its disruption induces adaptive physiologic changes in response to elevated iron demand, potentially serving as a mechanism to sustain increased erythropoietic demand.

PTEN-induced kinase PINK1 supports colorectal cancer growth by regulating the labile iron pool

Mitophagy is a cargo-specific autophagic process that recycles damaged mitochondria to promote mitochondrial turnover. PTEN-induced putative kinase 1 (PINK1) mediates the canonical mitophagic pathway. However, the role of PINK1 in diseases where mitophagy has been purported to play a role, such as colorectal cancer, is unclear. Our results here demonstrate that higher PINK1 expression is positively correlated with decreased colon cancer survival, and mitophagy is required for colon cancer growth. We show that doxycycline-inducible knockdown (KD) of PINK1 in a panel of colon cancer cell lines inhibited proliferation, whereas disruption of other mitophagy receptors did not impact cell growth. We observed that PINK KD led to a decrease in mitochondrial respiration, membrane hyperpolarization, accumulation of mitochondrial DNA, and depletion of antioxidant glutathione. In addition, mitochondria are important hubs for the utilization of iron and synthesizing iron-dependent cofactors such as heme and iron sulfur clusters. We observed an increase in the iron storage protein ferritin and a decreased labile iron pool in the PINK1 KD cells, but total cellular iron or markers of iron starvation/overload were not affected. Finally, cellular iron storage and the labile iron pool are maintained via autophagic degradation of ferritin (ferritinophagy). We found overexpressing nuclear receptor coactivator 4, a key adaptor for ferritinophagy, rescued cell growth and the labile iron pool in PINK1 KD cells. These results indicate that PINK1 integrates mitophagy and ferritinophagy to regulate intracellular iron availability and is essential for maintaining intracellular iron homeostasis to support survival and growth in colorectal cancer cells.

Hepatic SEL1L-HRD1 ER-associated degradation regulates systemic iron homeostasis via ceruloplasmin

Iron homeostasis is critical for cellular and organismal function and is tightly regulated to prevent toxicity or anemia due to iron excess or deficiency, respectively. However, subcellular regulatory mechanisms of iron remain largely unexplored. Here, we report that SEL1L-HRD1 protein complex of endoplasmic reticulum (ER)-associated degradation (ERAD) in hepatocytes controls systemic iron homeostasis in a ceruloplasmin (CP)-dependent, and ER stress-independent, manner. Mice with hepatocyte-specific Sel1L deficiency exhibit altered basal iron homeostasis and are sensitized to iron deficiency while resistant to iron overload. Proteomics screening for a factor linking ERAD deficiency to altered iron homeostasis identifies CP, a key ferroxidase involved in systemic iron distribution by catalyzing iron oxidation and efflux from tissues. Indeed, CP is highly unstable and a bona fide substrate of SEL1L-HRD1 ERAD. In the absence of ERAD, CP protein accumulates in the ER and is shunted to refolding, leading to elevated secretion. Providing clinical relevance of these findings, SEL1L-HRD1 ERAD is responsible for the degradation of a subset of disease-causing CP mutants, thereby attenuating their pathogenicity. Together, this study uncovers the role of SEL1L-HRD1 ERAD in systemic iron homeostasis and provides insights into protein misfolding-associated proteotoxicity.

Microenvironmental ammonia enhances T cell exhaustion in colorectal cancer

Effective therapies are lacking for patients with advanced colorectal cancer (CRC). The CRC tumor microenvironment has elevated metabolic waste products due to altered metabolism and proximity to the microbiota. The role of metabolite waste in tumor development, progression, and treatment resistance is unclear. We generated an autochthonous metastatic mouse model of CRC and used unbiased multi-omic analyses to reveal a robust accumulation of tumoral ammonia. The high ammonia levels induce T cell metabolic reprogramming, increase exhaustion, and decrease proliferation. CRC patients have increased serum ammonia, and the ammonia-related gene signature correlates with altered T cell response, adverse patient outcomes, and lack of response to immune checkpoint blockade. We demonstrate that enhancing ammonia clearance reactivates T cells, decreases tumor growth, and extends survival. Moreover, decreasing tumor-associated ammonia enhances anti-PD-L1 efficacy. These findings indicate that enhancing ammonia detoxification can reactivate T cells, highlighting a new approach to enhance the efficacy of immunotherapies.

NCOA4-Mediated Ferritinophagy Is a Pancreatic Cancer Dependency via Maintenance of Iron Bioavailability for Iron-Sulfur Cluster Proteins

Pancreatic ductal adenocarcinomas (PDAC) depend on autophagy for survival; however, the metabolic substrates that autophagy provides to drive PDAC progression are unclear. Ferritin, the cellular iron storage complex, is targeted for lysosomal degradation (ferritinophagy) by the selective autophagy adaptor NCOA4, resulting in release of iron for cellular utilization. Using patient-derived and murine models of PDAC, we demonstrate that ferritinophagy is upregulated in PDAC to sustain iron availability, thereby promoting tumor progression. Quantitative proteomics reveals that ferritinophagy fuels iron-sulfur cluster protein synthesis to support mitochondrial homeostasis. Targeting NCOA4 leads to tumor growth delay and prolonged survival but with the development of compensatory iron acquisition pathways. Finally, enhanced ferritinophagy accelerates PDAC tumorigenesis, and an elevated ferritinophagy expression signature predicts for poor prognosis in patients with PDAC. Together, our data reveal that the maintenance of iron homeostasis is a critical function of PDAC autophagy, and we define NCOA4-mediated ferritinophagy as a therapeutic target in PDAC.

SIGNIFICANCE

Autophagy and iron metabolism are metabolic dependencies in PDAC. However, targeted therapies for these pathways are lacking. We identify NCOA4-mediated selective autophagy of ferritin ("ferritinophagy") as upregulated in PDAC. Ferritinophagy supports PDAC iron metabolism and thereby tumor progression and represents a new therapeutic target in PDAC. See related commentary by Jain and Amaravadi, p. 2023. See related article by Ravichandran et al., p. 2198. This article is highlighted in the In This Issue feature, p. 2007.

The Role of Ferritin in Health and Disease: Recent Advances and Understandings

Systemic iron homeostasis needs to be tightly controlled, as both deficiency and excess iron cause major global health concerns, such as iron deficiency anemia, hemochromatosis, etc. In mammals, sufficient dietary acquisition is critical for fulfilling the systemic iron requirement. New questions are emerging about whether and how cellular iron transport pathways integrate with the iron storage mechanism. Ferritin is the intracellular iron storage protein that stores surplus iron after all the cellular needs are fulfilled and releases it in the face of an acute demand. Currently, there is a surge in interest in ferritin research after the discovery of novel pathways like ferritinophagy and ferroptosis. This review emphasizes the most recent ferritin-related discoveries and their impact on systemic iron regulation.

Protocol for isolation and analysis of small volatile microbiome metabolites from human or mouse samples

Metabolites are crucial for bidirectional communication between host and microbiome. We describe a protocol for the isolation of organic and aqueous metabolites from mucosal scrapes and feces from mouse and human samples. Although some of the most reactive organic compounds may be lost, this approach generates a functionally reproducible metabolic extract containing both host and microbial compounds appropriate for quantitative mass spectrometry and functional characterization. Our mass spectrometry approach identifies low-abundant and difficult to identify microbially derived metabolites.

For complete details on the use and execution of this protocol, please refer to Bell et al. (2021) and Das et al. (2020).

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Quickly isolates microbial metabolites from human or mouse feces or tissue

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Metabolites can be quantified and used for in vitro or in vivo applications

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Organic or aqueous metabolites can be isolated separately

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Identifies low-abundant and difficult to identify microbially derived metabolites

Modulation of the HIF2α-NCOA4 axis in enterocytes attenuates iron loading in a mouse model of hemochromatosis

Intestinal iron absorption is activated during increased systemic demand for iron. The best-studied example is iron deficiency anemia, which increases intestinal iron absorption. Interestingly, the intestinal response to anemia is very similar to that of iron overload disorders, as both the conditions activate a transcriptional program that leads to a hyperabsorption of iron via the transcription factor hypoxia-inducible factor 2α (HIF2α). However, pathways for selective targeting of intestine-mediated iron overload remain unknown. Nuclear receptor coactivator 4 (NCOA4) is a critical cargo receptor for autophagic breakdown of ferritin and the subsequent release of iron, in a process termed ferritinophagy. Our work demonstrates that NCOA4-mediated intestinal ferritinophagy is integrated into systemic iron demand via HIF2α. To demonstrate the importance of the intestinal HIF2α/ferritinophagy axis in systemic iron homeostasis, whole-body and intestine-specific NCOA4-/- mouse lines were generated and assessed. The analyses revealed that the intestinal and systemic response to iron deficiency was not altered after disruption of intestinal NCOA4. However, in a mouse model of hemochromatosis, ablation of intestinal NCOA4 was protective against iron overload. Therefore, NCOA4 can be selectively targeted for the management of iron overload disorders without disrupting the physiological processes involved in the response to systemic iron deficiency.

Reuterin in the healthy gut microbiome suppresses colorectal cancer growth through altering redox balance

Microbial dysbiosis is a colorectal cancer (CRC) hallmark and contributes to inflammation, tumor growth, and therapy response. Gut microbes signal via metabolites, but how the metabolites impact CRC is largely unknown. We interrogated fecal metabolites associated with mouse models of colon tumorigenesis with varying mutational load. We find that microbial metabolites from healthy mice or humans are growth-repressive, and this response is attenuated in mice and patients with CRC. Microbial profiling reveals that Lactobacillus reuteri and its metabolite, reuterin, are downregulated in mouse and human CRC. Reuterin alters redox balance, and reduces proliferation and survival in colon cancer cells. Reuterin induces selective protein oxidation and inhibits ribosomal biogenesis and protein translation. Exogenous Lactobacillus reuteri restricts colon tumor growth, increases tumor reactive oxygen species, and decreases protein translation in vivo. Our findings indicate that a healthy microbiome and specifically, Lactobacillus reuteri, is protective against CRC through microbial metabolite exchange.

Colorectal cancer cells utilize autophagy to maintain mitochondrial metabolism for cell proliferation under nutrient stress

Cancer cells reprogram cellular metabolism to maintain adequate nutrient pools to sustain proliferation. Moreover, autophagy is a regulated mechanism to break down dysfunctional cellular components and recycle cellular nutrients. However, the requirement for autophagy and the integration in cancer cell metabolism is not clear in colon cancer. Here, we show a cell-autonomous dependency of autophagy for cell growth in colorectal cancer. Loss of epithelial autophagy inhibits tumor growth in both sporadic and colitis-associated cancer models. Genetic and pharmacological inhibition of autophagy inhibits cell growth in colon cancer–derived cell lines and patient-derived enteroid models. Importantly, normal colon epithelium and patient-derived normal enteroid growth were not decreased following autophagy inhibition. To couple the role of autophagy to cellular metabolism, a cell culture screen in conjunction with metabolomic analysis was performed. We identified a critical role of autophagy to maintain mitochondrial metabolites for growth. Loss of mitochondrial recycling through inhibition of mitophagy hinders colon cancer cell growth. These findings have revealed a cell-autonomous role of autophagy that plays a critical role in regulating nutrient pools in vivo and in cell models, and it provides therapeutic targets for colon cancer.

HIF-2α activation potentiates oxidative cell death in colorectal cancers by increasing cellular iron

Hypoxia is a hallmark of solid tumors that promotes cell growth, survival, and metastasis and confers resistance to chemo and radiotherapies. Hypoxic responses are largely mediated by the transcription factors hypoxia-inducible factor 1α (HIF-1α) and HIF-2α. Our work demonstrates that HIF-2α is essential for colorectal cancer (CRC) progression. However, targeting hypoxic cells is difficult, and tumors rapidly acquire resistance to inhibitors of HIF-2α. To overcome this limitation, we performed a small molecule screen to identify HIF-2α-dependent vulnerabilities. Several known ferroptosis activators and dimethyl fumarate (DMF), a cell-permeable mitochondrial metabolite derivative, led to selective synthetic lethality in HIF-2α-expressing tumor enteroids. Our work demonstrated that HIF-2α integrated 2 independent forms of cell death via regulation of cellular iron and oxidation. First, activation of HIF-2α upregulated lipid and iron regulatory genes in CRC cells and colon tumors in mice and led to a ferroptosis-susceptible cell state. Second, via an iron-dependent, lipid peroxidation-independent pathway, HIF-2α activation potentiated ROS via irreversible cysteine oxidation and enhanced cell death. Inhibition or knockdown of HIF-2α decreased ROS and resistance to oxidative cell death in vitro and in vivo. Our results demonstrated a mechanistic vulnerability in cancer cells that were dependent on HIF-2α that can be leveraged for CRC treatment.

Linear lesions in dermatology: a clinicoaetiopathological study

BACKGROUND

Linear lesions are fairly common in our daily practice. However, the appearance of these lesions can vary, thus complicating the diagnosis.

AIMS

To study the various clinical presentations, the demographic profile of patients and the clinicopathological correlations of dermatoses presenting with a linear distribution.

METHODS

We conducted an institution-based, cross-sectional, descriptive study of 281 consecutive patients with linear lesions attending dermatology clinics. MedCalc software (V11.6) was used for statistical analysis.

RESULTS

Patients were divided into eight groups: lesions along the lines of Blaschko (n = 136), lesions along blood vessels (n = 3), lesions along lymphatics (n = 3), Koebner phenomenon (n = 24), autoinoculation (n = 24), external factors (n = 45), infestations (n = 2) and 'other' (n = 44). The mean age at presentation was 24.50 ± 18.82 years and the male/female ratio was 1.32 : 1. The commonest symptom was itching/burning (56.94% of patients), while the commonest site was the arm (44.48%); followed by the leg (30.60%), trunk and abdomen (22.42%), head and neck (19.20%), and genitalia (0.35%). Apart from the common cases, there was a wide gamut of rare conditions (e.g. angiokeratoma circumscriptum naeviforme, porokeratotic eccrine ostial and dermal duct naevus, Blaschko-linear syringocystadenoma papilliferum, progressive cribriform and zosteriform hyperpigmentation, unilateral naevoid acanthosis nigricans, fixed drug eruption, discoid lupus erythematosus).

CONCLUSION

Linear lesions act as diagnostic clues to many dermatological conditions, therefore, the importance of meticulous examination in clinical dermatology cannot be overemphasized.

Catheter-related blood stream infections: prevalence, risk factors and antimicrobial resistance pattern

Background

Intravascular devices have significant potential for producing iatrogenic diseases resulting in catheter-related blood stream infections (CRBSIs). A study was undertaken to find the prevalence of CRBSI among patients in acute wards and to analyze the associated risk factors, causative pathogens with their antibiotic susceptibility (ABST) patterns.

Methods

Randomly ten days per month were chosen, for a period of two years. All the acute wards patients who were on indwelling blood catheters were identified. Those fulfilling the CRBSI criteria were further worked up for confirmation of diagnosis by differential time to positivity. The catheter tip was cultured by Maki's semiquantitative method. ABST of the isolates obtained was performed by Kirby-Bauer disk diffusion method.

Results

The prevalence of CRBSI was found to be 39.25% with the most common organism isolate being Serratia marcescens (23.81%). The immunocompromised status of the patients and catheterisation time were significant risk factors. Methicillin resistance was found to be 33.33% in coagulase-negative staphylococci. The resistance to vancomycin among the Entercoccus faecium isolates was found to be 33.33%. Among the gram negatives, resistance to aminoglycosides, fluoroquinolones and third-generation cephalosporins was high.

Conclusion

The study highlights the importance of regular surveillance programs, an efficient infection control program, strict adherence to antiseptic measures and use of a rational antibiotic policy for the early diagnosis and better management of CRBSI.

Ferritinophagy is not required for colon cancer cell growth

Ferritinophagy is a form of selective autophagy responsible for degrading intracellular ferritin, mediated by nuclear receptor coactivator 4 (NCOA4). NCOA4 plays significant roles in systemic iron homeostasis, and its disruption leads to simultaneous anemia and susceptibility to iron overload. The importance of iron colorectal cancer pathogenesis is well studied; however, the role of ferritinophagy in colon cancer cell growth has not been assessed. Disruption of ferritinophagy via NCOA4 knockout leads to only marginal differences in growth under basal and iron-restricted conditions. Moreover, NCOA4 played no significant role in cell death induced by 5-fluorouracil and erastin. Western blotting analysis for ferritin and transferrin receptor 1 found a dose-dependent effect on expression in both proteins in wild-type and NCOA4 knockout cell lines, but further investigation revealed no difference in growth response when treated at both high and low doses. Our data demonstrate a marginal role for ferritinophagy in growth both under normal and cytotoxic conditions in colon cancer cells, as well as a possible compensatory mechanism in colon cancer cells in response to ferroptosis induction.

Impact of dietary manganese on experimental colitis in mice

Diet plays a significant role in the pathogenesis of inflammatory bowel disease (IBD). A recent epidemiological study has shown an inverse relationship between nutritional manganese (Mn) status and IBD patients. Mn is an essential micronutrient required for normal cell function and physiological processes. To date, the roles of Mn in intestinal homeostasis remain unknown and the contribution of Mn to IBD has yet to be explored. Here, we provide evidence that Mn is critical for the maintenance of the intestinal barrier and that Mn deficiency exacerbates dextran sulfate sodium (DSS)-induced colitis in mice. Specifically, when treated with DSS, Mn-deficient mice showed increased morbidity, weight loss, and colon injury, with a concomitant increase in inflammatory cytokine levels and oxidative and DNA damage. Even without DSS treatment, dietary Mn deficiency alone increased intestinal permeability by impairing intestinal tight junctions. In contrast, mice fed a Mn-supplemented diet showed slightly increased tolerance to DSS-induced experimental colitis, as judged by the colon length. Despite the well-appreciated roles of intestinal microbiota in driving inflammation in IBD, the gut microbiome composition was not altered by changes in dietary Mn. We conclude that Mn is necessary for proper maintenance of the intestinal barrier and provides protection against DSS-induced colon injury.

Microbial Metabolite Signaling Is Required for Systemic Iron Homeostasis

Iron is a central micronutrient needed by all living organisms. Competition for iron in the intestinal tract is essential for the maintenance of indigenous microbial populations and for host health. How symbiotic relationships between hosts and native microbes persist during times of iron limitation is unclear. Here, we demonstrate that indigenous bacteria possess an iron-dependent mechanism that inhibits host iron transport and storage. Using a high-throughput screen of microbial metabolites, we found that gut microbiota produce metabolites that suppress hypoxia-inducible factor 2α (HIF-2α) a master transcription factor of intestinal iron absorption and increase the iron-storage protein ferritin, resulting in decreased intestinal iron absorption by the host. We identified 1,3-diaminopropane (DAP) and reuterin as inhibitors of HIF-2α via inhibition of heterodimerization. DAP and reuterin effectively ameliorated systemic iron overload. This work provides evidence of intestine-microbiota metabolic crosstalk that is essential for systemic iron homeostasis.

Intestinal non-canonical NFκB signaling shapes the local and systemic immune response

Microfold cells (M-cells) are specialized cells of the intestine that sample luminal microbiota and dietary antigens to educate the immune cells of the intestinal lymphoid follicles. The function of M-cells in systemic inflammatory responses are still unclear. Here we show that epithelial non-canonical NFkB signaling mediated by NFkB-inducing kinase (NIK) is highly active in intestinal lymphoid follicles, and is required for M-cell maintenance. Intestinal NIK signaling modulates M-cell differentiation and elicits both local and systemic IL-17A and IgA production. Importantly, intestinal NIK signaling is active in mouse models of colitis and patients with inflammatory bowel diseases; meanwhile, constitutive NIK signaling increases the susceptibility to inflammatory injury by inducing ectopic M-cell differentiation and a chronic increase of IL-17A. Our work thus defines an important function of non-canonical NFkB and M-cells in immune homeostasis, inflammation and polymicrobial sepsis.

Microfold cells (M-cell) are specialized cells of the intestine that sample luminal microbiota and dietary antigens. Here the authors show that epithelial non-canonical NFκB signalling, as induced by NIK, is important for M-cells maintenance, yet constitutive NIK activation is associated with gut inflammation and inflammatory bowel disease.

SMAD family member 3 (SMAD3) and SMAD4 repress HIF2α-dependent iron-regulatory genes

Hypoxia-inducible factor 2α (HIF2α) directly regulates a battery of genes essential for intestinal iron absorption. Interestingly, iron deficiency and overload disorders do not result in increased intestinal expression of glycolytic or angiogenic HIF2α target genes. Similarly, inflammatory and tumor foci can induce a distinct subset of HIF2α target genes in vivo These observations indicate that different stimuli activate distinct subsets of HIF2α target genes via mechanisms that remain unclear. Here, we conducted a high-throughput siRNA-based screen to identify genes that regulate HIF2α's transcriptional activity on the promoter of the iron transporter gene divalent metal transporter-1 (DMT1). SMAD family member 3 (SMAD3) and SMAD4 were identified as potential transcriptional repressors. Further analysis revealed that SMAD4 signaling selectively represses iron-absorptive gene promoters but not the inflammatory or glycolytic HIF2α or HIF1α target genes. Moreover, the highly homologous SMAD2 did not alter HIF2α transcriptional activity. During iron deficiency, SMAD3 and SMAD4 expression was significantly decreased via proteasomal degradation, allowing for derepression of iron target genes. Several iron-regulatory genes contain a SMAD-binding element (SBE) in their proximal promoters; however, mutation of the putative SBE on the DMT1 promoter did not alter the repressive function of SMAD3 or SMAD4. Importantly, the transcription factor forkhead box protein A1 (FOXA1) was critical in SMAD4-induced DMT1 repression, and DNA binding of SMAD4 was essential for the repression of HIF2α activity, suggesting an indirect repressive mechanism through DNA binding. These results provide mechanistic clues to how HIF signaling can be regulated by different cellular cues.

Hepatic hepcidin/intestinal HIF-2α axis maintains iron absorption during iron deficiency and overload

Iron-related disorders are among the most prevalent diseases worldwide. Systemic iron homeostasis requires hepcidin, a liver-derived hormone that controls iron mobilization through its molecular target ferroportin (FPN), the only known mammalian iron exporter. This pathway is perturbed in diseases that cause iron overload. Additionally, intestinal HIF-2α is essential for the local absorptive response to systemic iron deficiency and iron overload. Our data demonstrate a hetero-tissue crosstalk mechanism, whereby hepatic hepcidin regulated intestinal HIF-2α in iron deficiency, anemia, and iron overload. We show that FPN controlled cell-autonomous iron efflux to stabilize and activate HIF-2α by regulating the activity of iron-dependent intestinal prolyl hydroxylase domain enzymes. Pharmacological blockade of HIF-2α using a clinically relevant and highly specific inhibitor successfully treated iron overload in a mouse model. These findings demonstrate a molecular link between hepatic hepcidin and intestinal HIF-2α that controls physiological iron uptake and drives iron hyperabsorption during iron overload.

Drug sensitivity pattern of various Staphylococcus species isolated at a tertiary care hospital

BACKGROUND

Staphylococcus aureus and other Staphylococcus species are important pathogenic organisms and are responsible for various hospital infections. These are the predominant organisms found in pus and blood culture isolates. Infections arising due to these bacterial isolates are difficult to treat because of developing multidrug resistance.

METHODS

Over a 1-year period at a tertiary care hospital laboratory, 524 Staphylococci species were isolated from pus, blood and urine samples and species-level identification was done.

RESULTS

S. aureus formed the predominant species (70.8%) followed by coagulase-negative Staphylococcus (CoNS) (29.20%). S. aureus (91%) was the main isolate from pus samples; however, CoNS was isolated in equally higher proportion in blood culture (63.58%). Among the CoNS, Staphylococcus hemolyticus was the main isolate (9.3%). β-Lactamase production, alteration of PBP and MLSB resistance were seen in variable degrees in different species.

CONCLUSION

CoNS group of Staphylococci is becoming an important cause of infection at tertiary care centres. The increased multidrug resistance among various Staphylococcus species is a cause of great concern and requires adequate measures to prevent the spread of these microorganisms in the hospital and the community.

Density functional theory study of the effect of helium clusters on tritium-containing palladium lattices

Density functional theory (DFT) calculations have been employed to calculate the energetics, structures and migration behaviour of helium in palladium tritides. Increasing the tritium concentration in palladium leads to a decrease in the formation energies of helium clusters, indicating that He clusters can form in the lattices. The calculated results show less lattice expansion in Pd defect-containing lattices compared to the perfect lattice owing to smaller lattice distortions. The lowest energy migration path for helium diffusion is along octahedral-tetrahedral-octahedral sites but the energy barrier increases with increasing tritium concentration. Repulsive interactions occur between Pd d and He s orbitals, suggesting that displacement of the metal atoms in the lattice leads to growth of pressure inside the lattices. This process may change the microstructural properties leading to the degradation of the material.

Preferential Iron Trafficking Characterizes Glioblastoma Stem-like Cells

Glioblastomas display hierarchies with self-renewing cancer stem-like cells (CSCs). RNA sequencing and enhancer mapping revealed regulatory programs unique to CSCs causing upregulation of the iron transporter transferrin, the top differentially expressed gene compared with tissue-specific progenitors. Direct interrogation of iron uptake demonstrated that CSCs potently extract iron from the microenvironment more effectively than other tumor cells. Systematic interrogation of iron flux determined that CSCs preferentially require transferrin receptor and ferritin, two core iron regulators, to propagate and form tumors in vivo. Depleting ferritin disrupted CSC mitotic progression, through the STAT3-FoxM1 regulatory axis, revealing an iron-regulated CSC pathway. Iron is a unique, primordial metal fundamental for earliest life forms, on which CSCs have an epigenetically programmed, targetable dependence.

Transvaginal sonography versus hysteroscopy in evaluation of abnormal uterine bleeding

BACKGROUND

Abnormal uterine bleeding (AUB) accounts for 33% of female patients referred to gynaecologists. Common causes of AUB include endometrial polyps, endometrial hyperplasia, submucous fibroids and anovulation. Accurate diagnosis of the cause of AUB can reduce the frequency of hysterectomy. This study was aimed at assessing the usefulness of TVS in comparison with hysteroscopy in AUB evaluation.

METHODS

100 female patients with AUB were enrolled in the study. Each patient was subjected to TVS where uterine cavity was studied in detail and hysteroscopy under anaesthesia using saline as distension medium. Sensitivity, specificity and predictive value of TVS as compared to hysteroscopy were calculated. Subgroup analysis within each group was also performed.

RESULTS

Menorrhagia was the commonest presenting symptom in the study population (n = 58) followed by metrorrhagia, menometrorrhagia and continuous bleeding >21 days. 74 female patients had normal size uterus. In 57 patients, the uterine cavity was normal on TVS. Thickened endometrium, endometrial polyp and submucous fibroids were seen in 19, 16 and 6 patients respectively. Hysteroscopy showed normal cavity in 59 female patients and polypoidal endometrium, polyps or submucous fibroids in 41. TVS was found to have high sensitivity and specificity (95.23 and 94.82 respectively) and high positive and negative predictive value. Strength of agreement between TVS and hysteroscopy was high (kappa value 0.898).

CONCLUSION

TVS is recommended as first line investigation in AUB. If TVS shows normal cavity, further evaluation can be omitted and patient started directly on medical treatment for her symptoms.

Computational modeling and analysis of iron release from macrophages

A major process of iron homeostasis in whole-body iron metabolism is the release of iron from the macrophages of the reticuloendothelial system. Macrophages recognize and phagocytose senescent or damaged erythrocytes. Then, they process the heme iron, which is returned to the circulation for reutilization by red blood cell precursors during erythropoiesis. The amount of iron released, compared to the amount shunted for storage as ferritin, is greater during iron deficiency. A currently accepted model of iron release assumes a passive-gradient with free diffusion of intracellular labile iron (Fe2+) through ferroportin (FPN), the transporter on the plasma membrane. Outside the cell, a multi-copper ferroxidase, ceruloplasmin (Cp), oxidizes ferrous to ferric ion. Apo-transferrin (Tf), the primary carrier of soluble iron in the plasma, binds ferric ion to form mono-ferric and di-ferric transferrin. According to the passive-gradient model, the removal of ferrous ion from the site of release sustains the gradient that maintains the iron release. Subcellular localization of FPN, however, indicates that the role of FPN may be more complex. By experiments and mathematical modeling, we have investigated the detailed mechanism of iron release from macrophages focusing on the roles of the Cp, FPN and apo-Tf. The passive-gradient model is quantitatively analyzed using a mathematical model for the first time. A comparison of experimental data with model simulations shows that the passive-gradient model cannot explain macrophage iron release. However, a facilitated-transport model associated with FPN can explain the iron release mechanism. According to the facilitated-transport model, intracellular FPN carries labile iron to the macrophage membrane. Extracellular Cp accelerates the oxidation of ferrous ion bound to FPN. Apo-Tf in the extracellular environment binds to the oxidized ferrous ion, completing the release process. Facilitated-transport model can correctly predict cellular iron efflux and is essential for physiologically relevant whole-body model of iron metabolism.

A rare case of gangrenous appendicitis by eggs of Taenia species

Cysticercosis and Taeniasis continue to be a major public health burden in the developing countries like India. Humans are the only definitive hosts infected by ingestion of eggs of Taenia species. Appendicular Taeniasis is rare with few isolated case reports during the past 30 years. Here, we report the case of a 38-year-old female patient from Nepal who presented with acute pain abdomen, was operated and diagnosed as suffering from gangrenous appendicitis caused by eggs of Taenia species.

Adolescent lumbar disc disease: findings and outcome

BACKGROUND

Lumbar disc herniation is mainly a disease of elderly people as degenerative changes progress with age.

RESULTS AND DISCUSSION

Present retrospective analysis was performed on 742 patients of lumbar disc disease operated over 11 years. Of 742 cases aged 20 years or less, 25 has been evaluated to see the clinical features, radiological features, operative findings, and outcome of lumbar disc surgery. The incidence of lumbar disc herniation in pediatric and adolescent populations was 3.5% (aged 20 years or less). All patients presented with low back pain with or without radiculopathy (n = 25). Diagnosis was easily made on magnetic resonance imaging. Gross degenerative changes in disc and end plates were uncommon (16%) in this population. The trauma may not be a predisposing factor in most of them. In 88% (n = 22) of the cases, only 1 level was affected; the commonest was L4-5 (n = 13). Disc herniation was centrolateral in 72% (n = 18) and central in 28% (n = 7). Disc was mostly soft, hydrated, and rubbery in 92% (n = 23). Disc herniation were subligamentous in 80% (n = 20) and extruded in 4% (n = 1). Sixteen percent (n = 4) of the patients had disc bulge with intact annulus.

CONCLUSIONS

Operative intervention in the form of simple discectomy offers good result in 92% (n = 23) cases irrespective of approach and method. Longer follow-up is mandatory because the chances of recurrence or another level involvement cannot be denied.

Reduction of mechanical heart valve thrombosis through a clinical audit

BACKGROUND AND AIM OF THE STUDY

Patients with mechanical heart valves implanted at four cardiothoracic centers were followed up in a hospital in Eastern India. Despite successful surgery and regular hospital visits, long-term survival was compromised by anticoagulation-related complications.

METHODS

Systematic analysis revealed under-anticoagulation in most patients. Thrombosis risk in 80 patients on regular follow up from 1989 to 1997 was 8.68 per 100 patient years (pt-yr). The incidence of both thrombotic and bleeding complications was reported as less than two per 100 pt-yr, when prothrombin time was consistently in the range of INR 2.5 to 3.9. In targeting this low event rate, impediments to optimum anticoagulation in the local set-up were identified. International Normalized Ratio (INR) was introduced to report prothrombin time (PT). Patients and doctors were educated about drug and diet interactions with oral anticoagulants (OAC) and the early features of valve thrombosis. Treatment protocols were evolved. The impact of the remedial measures was studied in 81 patients (64 old, 17 new) over a total of 254 pt-yr of follow up, from 1998 to 2001.

RESULTS

Thrombosis risk was reduced from 8.68 to 5.12 per 100 pt-yr, while non-fatal bleeding events increased from 0.28 to 1.96 per 100 pt-yr. Due to early recognition of occlusive prosthetic valve thrombosis and institution of fibrinolytic therapy, fatal events were reduced from 3.8 per 100 pt-yr to none for four consecutive years (statistically significant at 99% CI).

CONCLUSION

The clinical audit proved to be a valuable tool for understanding the problems in health care delivery, and bringing about improvement.

Renal artery involvement in patients of coronary artery disease undergoing coronary angiography--a prospective study

METHODS

We prospectively studied the angiographic incidence of renal artery stenosis in 1000 consecutive patients who underwent coronary angiography for clinically suspected coronary artery disease since December, 1998. Selective renal arteriography was performed in all the patients (mean age 57 years, 74.6% males) after coronary angiography.

RESULTS

Systemic arterial hypertension was present in 52%, 29.1% were smokers, 21% had diabetes and 31.2% had hypercholesterolemia. Significant coronary artery diseases was found in 849 (84.9%) patients. Of the total patient cohort, 103 (10.3%) patients had renal artery disease; 78 (7.8%) had insignificant stenosis (> 50%) and significant renal artery stenosis (< 50%) was identified in 25 (2.5%) patients. Three had bilateral renal artery stenosis. Comparisons were made between renal artery stenosis and risk factor profile. There was no statistically significant association between renal artery stenosis and parameters like diabetes mellitus, hypertension, smoking, lipid levels and serum creatinine.

CONCLUSION

In our study, the absolute number of cases with significant renal artery stenosis is small, so no statistical analysis could be performed to demonstrate the relationship of presence of renal artery stenosis with severity of CAD. However patients with severe coronary artery disease or having multiple risk factor showed a trend towards increased prevalence of renal artery stenosis, hence renal angiography should be done for this subset of patients.

Coronary stenting without pre-dilatation: an observational study

Conventional coronary stenting is done after pre-dilatation of the lesion. The bleeding complications and incidence of subacute stent thrombosis have been reduced significantly by the use of antiplatelet agents and high pressure balloon inflation to ensure complete stent expansion. Elective stenting also can be done without pre-dilatation by "stent alone technique." This approach significantly reduces the procedural cost and ischaemia time, avoiding potential complications such as abrupt vessel closure because of extensive dissection after conventional angioplasty and prior to stent deployment. Eighty patients of stable angina pectoris suitable for coronary angioplasty underwent stenting without pre-dilatation. Out of the 100 stents used, 38 were hand-crimped and 62 were pre-mounted. The target vessels were left anterior descending artery in 56 percent, right coronary artery in 32 percent and left circumflex in 12 percent. The procedure was successful in 88 percent lesions. In 12 percent stenting could be done only after pre-dilatation. In all these, there was proximal tortuosity and calcification. The fluoroscopy time was 10.2 +/- 4.5 minutes. The average number of balloons used per lesion was 1.08. Stent embolisation occurred in only one patient. There were no major adverse cardiac events in any of the patients. Thus stenting without pre-dilatation is safe. Patients who are eligible for stenting without pre-dilatation are those with stable angina pectoris without fluoroscopically visible calcium or coronary artery tortuosity and with lesions of moderate complexity.

Coil embolization of a giant atherosclerotic coronary artery aneurysm

The incidence of the coronary artery aneurysm varies from 1.5-5%. Atherosclerosis is the most common cause of coronary artery aneurysm in adults. A discrete, giant, saccular atherosclerotic coronary artery aneurysm in an artery without significant proximal stenosis is rare. We report the first such case of a giant atherosclerotic coronary artery aneurysm successfully treated with coil embolization.

Balloon mitral valvuloplasty with bifoil catheter: immediate and long-term follow-up results

This report documents clinical and hemodynamic benefits of balloon mitral valvuloplasty (BMV) using a bifoil balloon catheter from a single center in 415 consecutive cases of rheumatic mitral stenosis (MS). The procedure was successful in 396 (95.2%) patients, with an increase in mitral valve area (MVA) from 0.82+/-0.35 cm2 to 2.21+/-0.24 cm2 (P < 0.001). There were 2 (0.48%) in-hospital deaths, and 6 (1.44%) patients developed acute mitral regurgitation. The procedural and fluroscopy time was reduced significantly from 52+/-11 and 38+/-6 min to 33+/-7 and 19+/-5 min, respectively, after modifications of technique in our last 326 cases. The bifoil balloon catheter technique is safe and effective, and provides excellent hemodynamic benefits which are sustained at long-term follow-up. This technique should be considered as an addition to the existing armamentarium of interventional cardiologists performing mitral balloon valvuloplasty.

A University of California State-supported AIDS research award program--a unique state and university partnership in AIDS research

This article describes the State-supported University of California AIDS research award program and its major accomplishments. It shows how a partnership between a University and a State resulted in the formation of a successful, efficient, and cost-effective AIDS research award program. This program provides funds for rapid testing of investigator-initiated meritorious research ideas, new drugs, and treatment modalities. Funds were also utilized to establish three AIDS Clinical Research Centers, which evolved into regional consortia that coordinate trials of new drugs and other modalities. This program succeeded in involving investigators whose efforts have led to excellent medical care, advanced technologies, and new drugs for treating AIDS and AIDS-related diseases. The University remains committed to continuing support of all areas of AIDS research, emphasizing drug and vaccine development, pediatric AIDS, and AIDS prevention studies in groups at high risk for HIV infection.

Quantitative evaluation of peer review of program project and center applications in allergy and immunology

We compared the review patterns of applications for program projects and centers in allergy and immunology, reviewed by the National Institute of Allergy and Infectious Diseases review committee, with those of individual research projects in immunology, reviewed by three Division of Research Grants study sections. A high concordance between these review groups was obtained with respect to the application approval rate, mean score, and distribution of applications in various priority score ranges. Furthermore, we observed a high degree of consensus among reviewers on the quality of many program project and center applications, especially those with priority scores between 100 and 200.

In vitro susceptibility of Escherichia coli of swine origin to carbadox and other antimicrobials

Swine fecal Escherichia coli isolates were tested with the Microtiter broth dilution method for susceptibility to carbadox and 11 other antimicrobials. Of the 138 strains, 136 were resistant to sulfadiazine, 120 to tetracycline, 95 to streptomycin, and 63 to carbadox. Resistance to the remaining antimicrobials also was noted in various degrees, with the exception of amikacin, to which all strains were susceptible. Carbadox-resistant strains also were resistant to other antimicrobials. The multiple resistance pattern was most common to sulfadiazine and tetracycline or a combination of sulfadiazine, tetracycline, and streptomycin.

A note on fitness of haemoglobin genotypes in the Bengali-speaking population

In the Bengali-speaking population of Calcutta (India) the genotype frequencies of the Hb beta-A/E/T system are given. The fitness of the genotypes has been calculated. It is found that this system is not in stable or semistable equilibrium in this population.

A study on genetic selection and haemoglobin heterozygotes: Hb A/E and beta-thalassaemia trait

In this paper the genetic fitness of the two heterozygotes Hb A/E and β-thalassaemia trait, in Calcutta, is examined in terms of their reproductive performance. It is found from fertility that the heterozygote Hb A/E enjoys some selective advantage over the normal homozygote Hb A/A, but the other heterozygote (β-thalassaemia trait) does not. But from overall reproductive performance (fertility and infant mortality together) it is postulated that the heterozygotes will eventually suffer from a selective disadvantage in a place like Calcutta, where malaria was eradicated about three decades ago.