DDI2 Is a Ubiquitin-Directed Endoprotease Responsible for Cleavage of Transcription Factor NRF1.

The Ddi1/DDI2 proteins are ubiquitin shuttling factors, implicated in a variety of cellular functions. In addition to ubiquitin-binding and ubiquitin-like domains, they contain a conserved region with similarity to retroviral proteases, but whether and how DDI2 functions as a protease has remained unknown. Here, we show that DDI2 knockout cells are sensitive to proteasome inhibition and accumulate high-molecular weight, ubiquitylated proteins that are poorly degraded by the proteasome. These proteins are targets for the protease activity of purified DDI2. No evidence for DDI2 acting as a de-ubiquitylating enzyme was uncovered, which could suggest that it cleaves the ubiquitylated protein itself. In support of this idea, cleavage of transcription factor NRF1 is known to require DDI2 activity in vivo. We show that DDI2 is indeed capable of cleaving NRF1 in vitro but only when NRF1 protein is highly poly-ubiquitylated. Together, these data suggest that DDI2 is a ubiquitin-directed endoprotease.

Coordinated elimination of bacterial taxa optimally attenuates alloimmunity and prolongs allograft survival.

This study aimed to dissect the relationship between specific gut commensal bacterial subgroups, their functional metabolic pathways, and their impact on skin allograft outcome and alloimmunity. We previously showed that oral broad-spectrum antibiotic (Abx) pretreatment in mice delayed skin, heart, and lung allograft rejection and dampened alloimmune responses. Here, rationally designed Abx combinations targeting major bacterial groups were used to elucidate their individual contribution to modulating alloimmune responses. Abx cocktails targeting intestinal gram-negative, gram-positive, or anaerobic/gram-positive bacteria by oral gavage, all delayed skin allograft rejection, and reduced alloreactive T cell priming to different extents. Notably, the most pronounced extension of skin allograft survival and attenuation of alloimmunity were achieved when all gut bacterial groups were simultaneously targeted. These results suggest a model in which the strength of the alloimmune response is additively tuned up by gut microbial diversity. Shotgun metagenomic sequencing enabled strain-level resolution and identified a shared commensal, Parabacteroides distasonis, as the most enriched following all Abx treatments. Oral administration of P.distasonis to mice harboring a diverse microbiota significantly prolonged skin allograft survival, identifying a probiotic with therapeutic benefit in transplantation.

Microbiota-dependent and -independent effects of obesity on transplant rejection and hyperglycemia.

Obesity is associated with dysbiosis and a state of chronic inflammation that contributes to the pathogenesis of metabolic diseases, including diabetes. We have previously shown that obese mice develop glucose intolerance, increased alloreactivity, and accelerated transplant rejection. In the present study, we investigated the influence of the microbiota on diet-induced obesity (DIO)-associated transplant rejection and hyperglycemia. Antibiotic treatment prolonged graft survival and reduced fasting glycemia in high-fat diet (HFD)-fed specific-pathogen-free (SPF) mice, supporting a role for the microbiota in promoting accelerated graft rejection and hyperglycemia induced by DIO. Further supporting a microbiota-dependent effect, fecal microbiota transfer from DIO SPF mice into germ-free mice also accelerated graft rejection when compared with lean mice-fecal microbiota transfer. Notably, HFD could be also detrimental to the graft independently from microbiota, obesity, and hyperglycemia. Thus, whereas HFD-associated hyperglycemia was exclusively microbiota-dependent, HFD affected transplant outcomes via both microbiota-dependent and -independent mechanisms. Importantly, hyperglycemia in DIO SPF mice could be reduced by the addition of the gut commensal Alistipes onderdonkii, which alleviated both HFD-induced inflammation and glucose intolerance. Thus, microbial dysbiosis can be manipulated via antibiotics or select probiotics to counter some of the pathogenic effects of obesity in transplantation.

Oral administration of the commensal Alistipes onderdonkii prolongs allograft survival.

Intestinal commensals can exert immunomodulatory effects on the host, with beneficial or detrimental consequences depending on underlying diseases. We have previously correlated longer survival of minor mismatched skin grafts in mice with the presence of an intestinal commensal bacterium, Alistipes onderdonkii. In this study, we investigated its sufficiency and mechanism of action. Oral administration of A onderdonkii strain DSM19147 but not DSM108265 was sufficient to prolong minor mismatched skin graft survival through inhibition of tumor necrosis factor production. Through metabolomic and metagenomic comparisons between DSM19147 and DSM108265, we identified candidate gene products associated with the anti-inflammatory effect of DSM19147. A onderdonkii DSM19147 can lower inflammation both at a steady state and after transplantation and may serve as an anti-inflammatory probiotic beneficial for transplant recipients.

BORN TO WHEEZE OR LEARNED WHEN WE WERE YOUNG: MATERNAL AND ENVIRONMENTAL FACTORS INFLUENCE ATOPIC RISK.

The prevalence of atopic diseases is increasing globally, particularly in children. Heritable genetics can partially explain risk of disease. Evidence also points to acquired genetic material, in the form of the microbiome, as an important factor in disease pathogenesis. The acquisition of the microbiome dynamically changes in response to differences in lifestyle and environmental factors. Also, in utero, maternal and environmental factors influence atopic risk for allergic rhinitis, eczema, asthma, and food allergy. Combining the analytical power of omics, we focus on how the microbiota mediates effects between mother, environment, immunity, and risk of atopic disease. In parallel, we stress that health care disparities impact asthma morbidity and mortality. Efforts to improve asthma outcomes must include multidisciplinary strategies.

Host and gut microbial tryptophan metabolism and type 2 diabetes: an integrative analysis of host genetics, diet, gut microbiome and circulating metabolites in cohort studies.

OBJECTIVE: Tryptophan can be catabolised to various metabolites through host kynurenine and microbial indole pathways. We aimed to examine relationships of host and microbial tryptophan metabolites with incident type 2 diabetes (T2D), host genetics, diet and gut microbiota. METHOD: We analysed associations between circulating levels of 11 tryptophan metabolites and incident T2D in 9180 participants of diverse racial/ethnic backgrounds from five cohorts. We examined host genome-wide variants, dietary intake and gut microbiome associated with these metabolites. RESULTS: Tryptophan, four kynurenine-pathway metabolites (kynurenine, kynurenate, xanthurenate and quinolinate) and indolelactate were positively associated with T2D risk, while indolepropionate was inversely associated with T2D risk. We identified multiple host genetic variants, dietary factors, gut bacteria and their potential interplay associated with these T2D-relaetd metabolites. Intakes of fibre-rich foods, but not protein/tryptophan-rich foods, were the dietary factors most strongly associated with tryptophan metabolites. The fibre-indolepropionate association was partially explained by indolepropionate-associated gut bacteria, mostly fibre-using Firmicutes. We identified a novel association between a host functional LCT variant (determining lactase persistence) and serum indolepropionate, which might be related to a host gene-diet interaction on gut Bifidobacterium, a probiotic bacterium significantly associated with indolepropionate independent of other fibre-related bacteria. Higher milk intake was associated with higher levels of gut Bifidobacterium and serum indolepropionate only among genetically lactase non-persistent individuals. CONCLUSION: Higher milk intake among lactase non-persistent individuals, and higher fibre intake were associated with a favourable profile of circulating tryptophan metabolites for T2D, potentially through the host-microbial cross-talk shifting tryptophan metabolism toward gut microbial indolepropionate production.

Healthful eating patterns, serum metabolite profile and risk of diabetes in a population-based prospective study of US Hispanics/Latinos.

AIMS/HYPOTHESIS: We aimed to evaluate associations of multiple recommended dietary patterns (i.e. the alternate Mediterranean diet [aMED], the Healthy Eating Index [HEI]-2015 and the healthful Plant-based Diet Index [hPDI]) with serum metabolite profile, and to examine dietary-pattern-associated metabolites in relation to incident diabetes. METHODS: We included 2842 adult participants free from diabetes, CVD and cancer during baseline recruitment of the Hispanic Community Health Study/Study of Latinos. Metabolomics profiling of fasting serum was performed using an untargeted approach. Dietary pattern scores were derived using information collected by two 24 h dietary recalls. Dietary-pattern-associated metabolites were identified using multivariable survey linear regressions and their associations with incident diabetes were assessed using multivariable survey Poisson regressions with adjustment for traditional risk factors. RESULTS: We identified eight metabolites (mannose, γ/ß-tocopherol, N1-methylinosine, pyrraline and four amino acids) that were inversely associated with all dietary scores. These metabolites were detrimentally associated with various cardiometabolic risk traits, especially insulin resistance. A score comprised of these metabolites was associated with elevated risk of diabetes (RRper SD 1.54 [95% CI 1.29, 1.83]), and this detrimental association appeared to be attenuated or eliminated by having a higher score for aMED (pinteraction = 0.0001), HEI-2015 (pinteraction = 0.020) or hPDI (pinteraction = 0.023). For example, RR (95% CI) of diabetes for each SD increment in the metabolite score was 1.99 (1.44, 2.37), 1.67 (1.17, 2.38) and 1.08 (0.86, 1.34) across the lowest to the highest tertile of aMED score, respectively. CONCLUSIONS/INTERPRETATION: Various recommended dietary patterns were inversely related to a group of metabolites that were associated with elevated risk of diabetes. Adhering to a healthful eating pattern may attenuate or eliminate the detrimental association between metabolically unhealthy serum metabolites and risk of diabetes.

Transmission Dynamics of Large Coronavirus Disease Outbreak in Homeless Shelter, Chicago, Illinois, USA, 2020.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has the potential for rapid transmission in congregate settings. We describe the multidisciplinary response to an outbreak of coronavirus disease (COVID-19) in a large homeless shelter in Chicago, Illinois, USA. The response to the outbreak included 4 rounds of mass PCR testing of all staff and residents and subsequent isolation of persons who tested positive for SARS-CoV-2. We further describe the dynamics of the shelter outbreak by fitting a modified susceptible-exposed-infectious-recovered compartmental model incorporating the widespread SARS-CoV-2 testing and isolation measures implemented in this shelter. Our model demonstrates that rapid transmission of COVID-19 in the shelter occurred before the outbreak was detected; rates of transmission declined after widespread testing and isolation measures were put in place. Overall, we demonstrate the feasibility of mass PCR testing and isolation in congregate settings and suggest the necessity of prompt response to suspected COVID-19 outbreaks in homeless shelters.

Taurodeoxycholic acid and valine reverse obesity-associated augmented alloimmune responses and prolong allograft survival.

Obesity initiates a chronic inflammatory network linked to perioperative complications and increased acute rejection rates in organ transplantation. Bariatric surgery is the most effective treatment of obesity recommended for morbidly obese transplant recipients. Here, we delineated the effects of obesity and bariatric surgery on alloimmunity and transplant outcomes in diet-induced obese (DIO) mice. Allograft survival was significantly shorter in DIO-mice. When performing sleeve gastrectomies (SGx) prior to transplantation, we found attenuated T cell-derived alloimmune responses resulting in prolonged allograft survival. Administering taurodeoxycholic acid (TDCA) and valine, metabolites depleted in DIO-mice and restored through SGx, prolonged graft survival in DIO-mice comparable with SGx an dampened Th1 and Th17 alloimmune responses while Treg frequencies and CD4+ T cell-derived IL-10 production were augmented. Moreover, in recipient animals treated with TDCA/valine, levels of donor-specific antibodies had been reduced. Mechanistically, TDCA/valine restrained inflammatory M1-macrophage polarization through TGR5 that compromised cAMP signaling and inhibited macrophage-derived T cell activation. Consistently, administering a TGR5 agonist to DIO-mice prolonged allograft survival. Overall, we provide novel insights into obesity-induced inflammation and its impact on alloimmunity. Furthermore, we introduce TDCA/valine as a noninvasive alternative treatment for obese transplant patients.

LTR retroelement expansion of the human cancer transcriptome and immunopeptidome revealed by de novo transcript assembly.

Dysregulated endogenous retroelements (EREs) are increasingly implicated in the initiation, progression, and immune surveillance of human cancer. However, incomplete knowledge of ERE activity limits mechanistic studies. By using pan-cancer de novo transcript assembly, we uncover the extent and complexity of ERE transcription. The current assembly doubled the number of previously annotated transcripts overlapping with long-terminal repeat (LTR) elements, several thousand of which were expressed specifically in one or a few related cancer types. Exemplified in melanoma, LTR-overlapping transcripts were highly predictable, disease prognostic, and closely linked with molecularly defined subtypes. They further showed the potential to affect disease-relevant genes, as well as produce novel cancer-specific antigenic peptides. This extended view of LTR elements provides the framework for functional validation of affected genes and targets for cancer immunotherapy.

Men, suicide, and family and interpersonal violence: A mixed methods exploratory study.

Research has shown a link between gender, violence, and suicide. This relationship is complex, and few empirical studies have explored suicide and family and interpersonal violence perpetrated by men. Drawing on a coronial dataset of suicide cases and a mixed methods design, this study integrated a quantitative analysis of 155 suicide cases with a qualitative analysis of medico-legal reports from 32 cases. Findings showed different types and patterns of family and intimate partner violence for men who died by suicide. Men used violence in response to conflict, but also to dominate women. Cumulative, interwoven effects of violence, mental illness, alcohol and other drug use, socioeconomic, and psychosocial circumstances were observed in our study population. However, the use of violence and suicidal behaviour was also a deliberate and calculated response by which some men sought to maintain influence or control over women. Health and criminal justice interventions served as short-term responses to violence, mental illness, and suicidal behaviour, but were of limited assistance.

Effects of mental health training on capacity, willingness and engagement in peer-to-peer support in rural New South Wales.

ISSUE ADDRESSED: Rural Australians experience significant barriers in accessing mental health services, some of which may be overcome by increasing mental health literacy in rural communities. This paper evaluates Mental Health Support Skills (MHSS), short training courses developed by the Rural Adversity Mental Health Program (RAMHP). MHSS was designed to build the capacity of community members and gatekeepers to identify people with mental health concerns and link them to appropriate resources or services. METHODS: Program data from April 2017 to March 2020 were analysed to assess the reach and outcomes of MHSS training. Training feedback was collected through a post-training survey, completed directly after courses, and a follow-up survey two months after training. An app used by RAMHP coordinators (the trainers) recorded the geographic and demographic reach of courses. RESULTS: MHSS was provided to 10,208 residents across rural New South Wales. Survey participation was 49% (n = 4,985) for the post-training survey and 6% (n = 571), for the follow-up survey, two months post-training. The training was well-received and increased the mental health understanding and willingness to assist others of most respondents (91%-95%). Follow-up survey respondents applied learnings to assist others; 53% (n = 301) asked a total of 2,252 people about their mental health in the two months following training. Those in clinical roles asked a median of 6 people about their mental health, compared to 3 for those in nonclinical roles. Most follow-up survey respondents (59%, n = 339) reported doing more to look after their own mental health in the two months after training. CONCLUSION: These results are encouraging as they suggest that short-form mental health training can be an effective tool to address poorer mental health outcomes for rural residents by improving the ability of participants to help themselves and the people around them. SO WHAT?: Serious consideration should be given to short mental health courses, such as MHSS, to increase literacy and connection to services, especially in rural areas.

Lessons from the development and delivery of a rural suicide prevention program.

AIMS: Suicide prevention remains a priority in rural and remote Australia, where suicide rates continue to be higher than those in urban communities. This commentary describes the Good SPACE suicide prevention program, and the lessons learned from delivering this program over a 14-year period. CONTEXT: The Good SPACE program has been operating in rural New South Wales since 2007. The program focuses on educating rural community members to recognise the signs of suicide vulnerability, and how to take appropriate action if they encounter someone considering suicide. APPROACH: Communities are selected to receive Good SPACE training in consultation with key stakeholder organisations, or by request from communities. Across the life of the program, key challenges in its administration have included short-term funding arrangements and staff turnover. Strengths have included the ability to adapt content to meet the needs of rural communities (eg from an initial focus on helping farmers during periods of drought, to a broader focus on all rural residents and a wider range of adversities). As the program moves forward, emphasis will be placed on harder-to-reach populations, including males and those with lower mental health literacy. CONCLUSION: The Good SPACE program has ongoing funding to adapt its content and continue administration through the Rural Adversity Mental Health Program (https://www.ramhp.com.au/). The lessons learned throughout the life of the program might be of use to other organisations aiming to provide community-based education programs in rural and remote communities.

The olfactory G protein-coupled receptor (Olfr-78/OR51E2) modulates the intestinal response to colitis.

Olfactory receptor-78 (Olfr-78) is a recently identified G protein-coupled receptor activated by short-chain fatty acids acetate and propionate. A suggested role for this receptor exists in the prostate where it may influence chronic inflammatory response leading to intraepithelial neoplasia. Olfr-78 has also been shown to be expressed in mouse colon. Short-chain fatty acids and their receptors are well known to modulate inflammation in the gut. Considering this possibility, we first explored if colitis regulated Olfr-78 expression in the gut, where we observed a significant reduction in the expression of Olfr-78 transcript in mouse models of dextran sodium sulfate (DSS)- and 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis. To more directly test this, mice deficient in Olfr-78 were administered with DSS in water for 7 days and were found to have increased expression of IL-1ß and inflammatory signs in colon compared with control mice. Next, we explored the expression of its human counterpart olfactory receptor family 51, subfamily E, member 2 (OR51E2) in human intestinal samples and observed that it was in fact also expressed in human colon samples. RNA sequence analysis revealed significant changes in the genes involved in infection, immunity, inflammation, and colorectal cancer between wild-type and Olfr-78 knockout mice. Collectively, our findings show that Olfr-78 is highly expressed in colon and downregulated in DSS- and TNBS-induced colitis, and DSS-treated Olfr-78 null mice had increased colonic expression of cytokine RNA levels, suggesting a potential role for this receptor in intestinal inflammation. Future investigations are needed to understand how Olfr-78/OR51E2 in both mouse and human intestine modulates gastrointestinal pathophysiology.

Utilizing longitudinal microbiome taxonomic profiles to predict food allergy via Long Short-Term Memory networks.

Food allergy is usually difficult to diagnose in early life, and the inability to diagnose patients with atopic diseases at an early age may lead to severe complications. Numerous studies have suggested an association between the infant gut microbiome and development of allergy. In this work, we investigated the capacity of Long Short-Term Memory (LSTM) networks to predict food allergies in early life (0-3 years) from subjects' longitudinal gut microbiome profiles. Using the DIABIMMUNE dataset, we show an increase in predictive power using our model compared to Hidden Markov Model, Multi-Layer Perceptron Neural Network, Support Vector Machine, Random Forest, and LASSO regression. We further evaluated whether the training of LSTM networks benefits from reduced representations of microbial features. We considered sparse autoencoder for extraction of potential latent representations in addition to standard feature selection procedures based on Minimum Redundancy Maximum Relevance (mRMR) and variance prior to the training of LSTM networks. The comprehensive evaluation reveals that LSTM networks with the mRMR selected features achieve significantly better performance compared to the other tested machine learning models.

Connecting with social and emotional well-being in rural Australia: An evaluation of 'We-Yarn', an Aboriginal gatekeeper suicide prevention workshop.

OBJECTIVE: This evaluation considered the potential of We-Yarn, a suicide prevention gatekeeper training workshop, to contribute to Aboriginal suicide prevention in rural New South Wales. DESIGN: A mixed methods approach included surveys, in-depth interviews and workshop observations. SETTING: Aboriginal suicide prevention training in rural New South Wales, Australia. PARTICIPANTS: Attendees at We-Yarn training. INTERVENTION: We-Yarn provided culturally safe suicide prevention skills training for Aboriginal people and for those who work with Aboriginal communities and persons in rural New South Wales. Training workshops were delivered across multiple locations for 6 hours in one day. Workshops were facilitated by two facilitators with lived and professional experience; one Aboriginal and one non-Aboriginal facilitator. We-Yarn content was developed by staff from the Centre for Rural and Remote Mental Health, and in consultation with Aboriginal Elders and representatives of Aboriginal Medical Services to ensure relevance and cultural appropriateness. MAIN OUTCOME MEASURES: Pre and post-workshop surveys captured capacity and participants' confidence in identifying and responding to a person at risk of suicide. Interviews explored participants' experiences of workshops, implementation of learning, and attitudes regarding social and emotional wellbeing and suicide. Observations detailed the workshop environment, participants' engagement, and participants' responses to facilitators and content. RESULTS: We-Yarn was considered culturally appropriate. Participants responded to facilitators' lived experiences. Participants reported significant improvements in understanding the links between cultural strengths, social and emotional wellbeing and suicide prevention. However, health professionals with existing knowledge wanted a stronger focus on clinical training. CONCLUSION: We-Yarn promoted discussion of suicide prevention within a holistic health framework, building on participants' pre-existing knowledge about social and emotional wellbeing. Importantly, skilful facilitators with lived experience were vital to the success of the workshops. Consideration should be given to attracting people with low suicide prevention knowledge to the workshops, developing tailored workshops for health professionals and ensuring prolonged engagement with communities. Multifaceted and long term responses in addition to this type of training are important.

Developing a mobile data collection tool to manage a dispersed mental health workforce.

CONTEXT: The Rural Adversity Mental Health Program (RAMHP) connects people who need mental health assistance in rural and remote New South Wales (NSW), Australia with appropriate services and resources. In 2016, RAMHP underwent a comprehensive reorientation to meet new state and federal priorities. A full assessment of program data collection methods for management, monitoring and evaluation was undertaken. Reliable data were needed to ensure program fidelity and to assess program performance. ISSUES: The review indicated that existing data collection methods provided limited and unreliable information, were inconvenient for RAMHP coordinators to use and unsuited to their itinerant role. A mobile collection tool (app) was developed to address RAMHP activity data needs. A design and implementation process was followed to optimise data collection and to ensure the successful use of the app by coordinators. LESSONS LEARNED: The early planning investment was worthwhile, the app was successfully adopted by the coordinators and a much improved data collection capability was achieved. Moreover, data capture increased, while errors decreased. Data are more reliable, specific, timely and informative and are used for strategic and operational planning and to demonstrate program performance.

In Situ Methane Determination in Petroleum at High Temperatures and High Pressures with Multivariate Optical Computing.

Multivariate optical computing (MOC) is a compressed sensing technique enabling the measurement of analytes in a complex interfering mixture under harsh conditions. In this work, we describe the design, modeling, fabrication, and validation of a sensor for the measurement of dissolved methane in petroleum crude oil at high and variable combinations of pressure (up to 82.727 MPa) and temperature (up to 121.1 °C). Both laboratory and field validation results are presented, with five separate MOC sensors yielding a RMS error of 0.0089 g/cm3 methane in high pressure/high temperature laboratory and field samples compared to 0.0086 g/cm3 methane for a room temperature laboratory Fourier transform infrared (FTIR) spectrometer using partial least-squares (PLS) regression models.

Prenatal Maternal Depression and Neonatal Immune Responses.

OBJECTIVE: The aim of the study was to examine the association of lifetime maternal depression with regulation of immune responses in the infant, measured by cytokine levels and lymphocyte proliferation (LP) in cord blood mononuclear cells collected at delivery. METHODS: We studied women recruited in early pregnancy into the Project Viva longitudinal cohort who had cord blood assayed after delivery (N = 463). Women reported about depressive symptoms in midpregnancy (Edinburgh Postnatal Depression Scale) and depression history by questionnaire. Immune responses were assayed by an index of LP, and concentrations of five cytokines (interleukin [IL]-6, IL-10, IL-13, tumor necrosis tumor necrosis factor factor α, and interferon γ) after incubation of cord blood mononuclear cells either in medium alone or stimulated with phytohemagglutinin (PHA), cockroach extract, or house dust mite extract. We examined associations of maternal depression with these sets of cytokine measures using multivariable linear or tobit regression analyses. RESULTS: After adjustment for confounders (mother's age, race/ethnicity, education, household income, season of birth, and child sex), levels of IL-10 after stimulation with cockroach or dust mite allergen were lower in cord blood from ever versus never depressed women, and a similar trend was evident in IL-10 stimulated with PHA (percentage difference: cockroach extract = -41.4, p = .027; house dust mite extract = 1-36.0, p = .071; PHA = -24.2, p = .333). No significant differences were seen in levels of other cytokines or LP. CONCLUSIONS: Maternal depression is associated with offspring immune responses at birth, which may have implications for later life atopic risk or immune function.

In vitro antioxidant activities of Rhodobacter sphaeroides and protective effect on Caco-2 cell line model.

The present study aimed to evaluate the in vitro antioxidant activities and the protective effect of Rhodobacter sphaeroides on H2O2-induced oxidative stress in Caco-2 cells. The results showed that the antioxidant action of R. sphaeroides varied with different cell concentrations and treatments. Also, the intact cells and intracellular cell-free extracts showed better antioxidant activities. Caco-2 cell-based oxidative stress model was developed by optimizing H2O2 concentration and culture time with the half lethal dose and methyl thiazolyl tetrazolium. By increasing the activity of endogenous antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase, upregulating the antioxidant ability of the anti-superoxide anion and anti-hydroxyl radical, R. sphaeroides, especially the mutant strain R. sphaeroides (CGMCC No. 8513), exhibited significant protective activity against H2O2-induced oxidative stress in Caco-2 cells. Taken together, R. sphaeroides (CGMCC No. 8513) exhibits strong antioxidant activities and is a candidate to be investigated as a potential probiotic in the future.