Role of TLR4 in the gut-brain axis in Parkinson's disease: a translational study from men to mice

OBJECTIVE

Recent evidence suggesting an important role of gut-derived inflammation in brain disorders has opened up new directions to explore the possible role of the gut-brain axis in neurodegenerative diseases. Given the prominence of dysbiosis and colonic dysfunction in patients with Parkinson's disease (PD), we propose that toll-like receptor 4 (TLR4)-mediated intestinal dysfunction could contribute to intestinal and central inflammation in PD-related neurodegeneration.

DESIGN

To test this hypothesis we performed studies in both human tissue and a murine model of PD. Inflammation, immune activation and microbiota composition were measured in colonic samples from subjects with PD and healthy controls subjects and rotenone or vehicle-treated mice. To further assess the role of the TLR4 signalling in PD-induced neuroinflammation, we used TLR4-knockout (KO) mice in conjunction with oral rotenone administration to model PD.

RESULTS

Patients with PD have intestinal barrier disruption, enhanced markers of microbial translocation and higher pro-inflammatory gene profiles in the colonic biopsy samples compared with controls. In this regard, we found increased expression of the bacterial endotoxin-specific ligand TLR4, CD3+ T cells, cytokine expression in colonic biopsies, dysbiosis characterised by a decrease abundance of SCFA-producing colonic bacteria in subjects with PD. Rotenone treatment in TLR4-KO mice revealed less intestinal inflammation, intestinal and motor dysfunction, neuroinflammation and neurodegeneration, relative to rotenone-treated wild-type animals despite the presence of dysbiotic microbiota in TLR4-KO mice.

CONCLUSION

Taken together, these studies suggest that TLR4-mediated inflammation plays an important role in intestinal and/or brain inflammation, which may be one of the key factors leading to neurodegeneration in PD.

Wnt signaling in bone, kidney, intestine, and adipose tissue and interorgan interaction in aging

Over the last two decades, it has become increasingly apparent that Wnt signaling plays a critical role in development and adult tissue homeostasis in multiple organs and in the pathogenesis of many diseases. In particular, a crucial role for Wnt signaling in bone development and bone tissue homeostasis has been well recognized. Numerous genome-wide association studies confirmed the importance of Wnt signaling in controlling bone mass. Moreover, ample evidence suggests that Wnt signaling is essential for kidney, intestine, and adipose tissue development and homeostasis. Recent emerging evidence demonstrates that Wnt signaling may play a fundamental role in the aging process of those organs. New discoveries show that bone is not only the major reservoir for calcium and phosphate storage, but also the largest organ with multiple functions, including mineral and energy metabolism. The interactions among bone, kidney, intestine, and adipose tissue are controlled and regulated by several endocrine signals, including FGF23, klotho, sclerostin, osteocalcin, vitamin D, and leptin. Since the aging process is characterized by structural and functional decline in almost all tissues and organs, understanding the Wnt signaling-related interactions among bone, kidney, intestine, and adipose tissue in aging may shed light on the pathogenesis of age-related diseases.

Circadian Mechanisms in Alcohol Use Disorder and Tissue Injury

Heavy use of alcohol can lead to addictive behaviors and to eventual alcohol-related tissue damage. While increased consumption of alcohol has been attributed to various factors including level of alcohol exposure and environmental factors such as stress, data from behavioral scientists and physiological researchers are revealing roles for the circadian rhythm in mediating the development of behaviors associated with alcohol use disorder as well as the tissue damage that drives physiological disease. In this work, we compile recent work on the complex mutually influential relationship that exists between the core circadian rhythm and the pharmacodynamics of alcohol. As we do so, we highlight implications of the relationship between alcohol and common circadian mechanisms of effected organs on alcohol consumption, metabolism, toxicity, and pathology.

Pharmacological targeting of the mammalian clock reveals a novel analgesic for osteoarthritis-induced pain

Environmental disruption of the circadian rhythm is linked with increased pain due to osteoarthritis (OA). We aimed to characterize the role of the clock gene in OA-induced pain more systemically using both genetic and pharmacological approaches. Genetically modified mice, (bmal1f/fNav1.8CreERT mice), generated by deleting the critical clock gene, bmal1, from Nav1.8 sensory neurons, were resistant to the development of mechanical hyperalgesia associated with OA induced by partial medial meniscectomy (PMM) of the knee. In wild-type mice, induction of OA by PMM surgery led to a substantial increase in BMAL1 expression in DRG neurons. Interestingly, pharmacological activation of the REV-ERB (a negative regulator of bmal1 transcription) with SR9009 resulted in reduction of BMAL1 expression, and a significant decrease in mechanical hyperalgesia associated with OA. Cartilage degeneration was also significantly reduced in mice treated with the REV-ERB agonist SR9009. Based on these data, we also assessed the effect of pharmacological activation of REV-ERB using a model of environmental circadian disruption with its associated mechanical hyperalgesia, and noted that SR9009 was an effective analgesic in this model as well. Our data clearly demonstrate that genetic disruption of the molecular clock, via deletion of bmal1 in the sensory neurons of the DRG, decreases pain in a model of OA. Furthermore, pharmacological activation of REV-ERB leading to suppression of BMAL1 expression may be an effective method for treating OA-related pain, as well as to reduce joint damage associated with this disease.

Dietary Fiber Treatment Corrects the Composition of Gut Microbiota, Promotes SCFA Production, and Suppresses Colon Carcinogenesis

Epidemiological studies propose a protective role for dietary fiber in colon cancer (CRC). One possible mechanism of fiber is its fermentation property in the gut and ability to change microbiota composition and function. Here, we investigate the role of a dietary fiber mixture in polyposis and elucidate potential mechanisms using TS4Cre × cAPC^l°^x468 mice. Stool microbiota profiling was performed, while functional prediction was done using PICRUSt. Stool short-chain fatty acid (SCFA) metabolites were measured. Histone acetylation and expression of SCFA butyrate receptor were assessed. We found that SCFA-producing bacteria were lower in the polyposis mice, suggesting a decline in the fermentation product of dietary fibers with polyposis. Next, a high fiber diet was given to polyposis mice, which significantly increased SCFA-producing bacteria as well as SCFA levels. This was associated with an increase in SCFA butyrate receptor and a significant decrease in polyposis. In conclusion, we found polyposis to be associated with dysbiotic microbiota characterized by a decline in SCFA-producing bacteria, which was targetable by high fiber treatment, leading to an increase in SCFA levels and amelioration of polyposis. The prebiotic activity of fiber, promoting beneficial bacteria, could be the key mechanism for the protective effects of fiber on colon carcinogenesis. SCFA-promoting fermentable fibers are a promising dietary intervention to prevent CRC.

The Potential Role of Gut-Derived Inflammation in Multiple System Atrophy

BACKGROUND

Recent evidence suggests that Parkinson's disease (PD) is associated with intestinal microbiota dysbiosis, abnormal intestinal permeability, and intestinal inflammation.

OBJECTIVE

Our study aimed to determine if these gut abnormalities are present in another synucleinopathy, multiple system atrophy (MSA).

METHODS

In six MSA and 11 healthy control subjects, we performed immunohistochemistry studies of colonic sigmoid mucosa to evaluate the intestinal barrier marker Zonula Occludens-1 and the endotoxin-related inflammation marker Toll-like-receptor-4 expression. We also assessed colonic sigmoid mucosal and fecal microbiota compositions using high-throughput 16S ribosomal RNA gene amplicon sequencing.

RESULTS

MSA subjects showed disrupted tight junction protein Zonula Occludens-1 structure in sigmoid mucosa tissue suggesting intestinal barrier dysfunction. The lipopolysaccharide specific inflammatory receptor Toll-like-receptor-4 was significantly higher in the colonic sigmoid mucosa in MSA relative to healthy controls. Microbiota analysis suggested high relative abundance of gram-negative, putative "pro-inflammatory" bacteria in various family and genus level taxa, from the phylum Bacteroidetes and Proteobacteria, in MSA feces and mucosa. At the taxonomic level of genus, putative "anti-inflammatory" butyrate-producing bacteria were less abundant in MSA feces. Predictive functional analysis indicated that the relative abundance of a number of genes involved in metabolism were lower in MSA feces, whereas the relative abundance of genes involved in lipopolysaccharide biosynthesis were higher in both MSA feces and mucosa compared to healthy controls.

CONCLUSIONS

This proof-of-concept study provides preliminary evidence that like PD, MSA subjects display evidence of disrupted intestinal barrier integrity, increased marker of endotoxin-related intestinal inflammation, and pro-inflammatory colonic microbiota.

Colon dysregulation in methamphetamine self-administering HIV-1 transgenic rats

The integrity and function of the gut is impaired in HIV-infected individuals, and gut pathogenesis may play a role in several HIV-associated disorders. Methamphetamine is a popular illicit drug abused by HIV-infected individuals. However, the effect of methamphetamine on the gut and its potential to exacerbate HIV-associated gut pathology is not known. To shed light on this scenario, we evaluated colon barrier pathology in a rat model of the human comorbid condition. Intestinal barrier integrity and permeability were assessed in drug-naïve Fischer 344 HIV-1 transgenic (Tg) and non-Tg rats, and in Tg and non-Tg rats instrumented with jugular cannulae trained to self-administer methamphetamine or serving as saline-yoked controls. Intestinal permeability was determined by measuring the urine content of orally gavaged sugars. Intestinal barrier integrity was evaluated by immunoblotting or immunofluorescence of colon claudin-1 and zonula occludens-1 (ZO-1), two major tight junction proteins that regulate gut epithelial paracellular permeability. Both non-Tg and Tg rats self-administered moderate amounts of methamphetamine. These amounts were sufficient to increase colon permeability, reduce protein level of claudin-1, and reduce claudin-1 and ZO-1 immunofluorescence in Tg rats relative to non-Tg rats. Methamphetamine decreased tight junction immunofluorescence in non-Tg rats, with a similar, but non-significant trend observed in Tg rats. However, the effect of methamphetamine on tight junction proteins was subthreshold to gut leakiness. These findings reveal that both HIV-1 proteins and methamphetamine alter colon barrier integrity, and indicate that the gut may be a pathogenic site for these insults.

Diurnal variations in intestinal barrier integrity and liver pathology in mice: implications for alcohol binge

Recent studies suggest that circadian rhythms regulate intestinal barrier integrity, but it is not clear whether there are daily variations in barrier integrity. This study investigated daily variations in intestinal barrier integrity, including whether there are differences in alcohol-induced intestinal barrier dysfunction after an alcohol binge at different times of day and whether this is associated with concurrent liver injury. C57BL6/J male mice were fed a standard chow diet, an alcohol-containing liquid diet, or an alcohol control diet for 4 wk. During week 5 (i.e., on days 43-45), mice received three once-daily gavages of alcohol (6 g/kg) or the control (phosphate-buffered saline) at the same time each day. Immediately after the binge on the second day, intestinal permeability was assessed. Four hours after the third and final binge, mice were euthanized and tissue samples collected. The results demonstrated diet-specific and outcome-specific effects of time, alcohol, and/or time by alcohol interaction. Specifically, the alcohol binge robustly influenced markers of intestinal barrier integrity, and liver markers were robustly influenced by time of day. Only intestinal permeability (i.e., sucralose) demonstrated a significant effect of time and also showed a binge by time interaction, suggesting that the time of the alcohol binge influences colonic permeability. NEW & NOTEWORTHY This study investigated daily variations in intestinal barrier integrity, including whether there are differences in alcohol-induced intestinal barrier dysfunction after an alcohol binge at different times of day and whether this is associated with concurrent liver injury. We conclude that 1) alcohol binge significantly impacted markers of intestinal permeability, 2) time of day significantly affected liver outcomes, and 3) the time of day influenced colonic permeability.

Alcohol Feeding in Mice Promotes Colonic Hyperpermeability and Changes in Colonic Organoid Stem Cell Fate

BACKGROUND

Alcohol increases intestinal permeability to proinflammatory microbial products that promote liver disease, even after a period of sobriety. We sought to test the hypothesis that alcohol affects intestinal stem cells using an in vivo model and ex vivo organoids generated from jejunum and colon from mice fed chronic alcohol.

METHODS

Mice were fed a control or an alcohol diet. Intestinal permeability, liver steatosis-inflammation, and stool short-chain fatty acids (SCFAs) were measured. Jejunum and colonic organoids and tissue were stained for stem cell, cell lineage, and apical junction markers with assessment of mRNA by PCR and RNA-seq. ChIP-PCR analysis was carried out for Notch1 using an antibody specific for acetylated histone 3.

RESULTS

Alcohol-fed mice exhibited colonic (but not small intestinal) hyperpermeability, steatohepatitis, and decreased butyrate/total SCFA ratio in stool. Stem cell, cell lineage, and apical junction marker staining in tissue or organoids from jejunum tissue were not impacted by alcohol. Only chromogranin A (Chga) was increased in jejunum organoids by qPCR. However, colonic tissue and organoid staining exhibited an alcohol-induced significant decrease in cytokeratin 20+  (Krt20+) absorptive lineage enterocytes, a decrease in occludin and E-cadherin apical junction proteins, an increase in Chga, and an increase in the Lgr5 stem cell marker. qPCR revealed an alcohol-induced decrease in colonic organoid and tissue Notch1, Hes1, and Krt20 and increased Chga, supporting an alteration in stem cell fate due to decreased Notch1 expression. Colonic tissue ChIP-PCR revealed alcohol feeding suppressed Notch1 mRNA expression (via deacetylation of histone H3) and decreased Notch1 tissue staining.

CONCLUSIONS

Data support a model for alcohol-induced colonic hyperpermeability via epigenetic effects on Notch1, and thus Hes1, suppression through a mechanism involving histone H3 deacetylation at the Notch1 locus. This decreased enterocyte and increased enteroendocrine cell colonic stem cell fate and decreased apical junctional proteins leading to hyperpermeability.

CREB Protein Mediates Alcohol-Induced Circadian Disruption and Intestinal Permeability

BACKGROUND

Alcoholic liver disease (ALD) is commonly associated with intestinal permeability. An unanswered question is why only a subset of heavy alcohol drinkers develop endotoxemia. Recent studies suggest that circadian disruption is the susceptibility factor for alcohol-induced gut leakiness to endotoxins. The circadian protein PER2 is increased after exposure to alcohol and siRNA knockdown of PER2 in vitro blocks alcohol-induced intestinal barrier dysfunction. We have shown that blocking CYP2E1 (i.e., important for alcohol metabolism) with siRNA inhibits the alcohol-induced increase in PER2 and suggesting that oxidative stress may mediate alcohol-induced increase in PER2 in intestinal epithelial cells. The aim of this study was to elucidate whether a mechanism incited by alcohol-derived oxidative stress mediates the transcriptional induction of PER2 and subsequent intestinal hyperpermeability.

METHODS

Caco-2 cells were exposed to 0.2% alcohol with or without pretreatment with modulators of oxidative stress or PKA activity. Permeability of the Caco-2 monolayer was assessed by transepithelial electrical resistance. Protein expression was measured by Western blot and mRNA with real-time polymerase chain reaction. Wild-type C57BL/6J mice were fed with alcohol diet (29% of total calories, 4.5% v/v) for 8 weeks. Western blot was used to analyze PER2 expression in mouse proximal colon tissue.

RESULTS

Alcohol increased oxidative stress, caused Caco-2 cell monolayer dysfunction, and increased levels of the circadian clock proteins PER2 and CLOCK. These effects were mitigated by pretreatment of Caco-2 cells with an antioxidant scavenger. Alcohol-derived oxidative stress activated cAMP response element-binding (CREB) via the PKA pathway and increased PER2 mRNA and protein. Inhibiting CREB prevented the increase in PER2 and Caco-2 cell monolayer hyperpermeability.

CONCLUSIONS

Taken together, these data suggest that strategies to reduce alcohol-induced oxidative stress may alleviate alcohol-mediated circadian disruption and intestinal leakiness, critical drivers of ALD.

Alcohol Injury Damages Intestinal Stem Cells

BACKGROUND

Alcohol consumption is associated with intestinal injury including intestinal leakiness and the risk of developing progressive gastrointestinal cancer. Alcoholics have disruption of intestinal barrier dysfunction that persists weeks after stopping alcohol intake, and this occurs in spite of the fact that intestinal epithelial cells turn over every 3 to 5 days. The renewal and functional regulation of the intestinal epithelium largely relies on intestinal stem cells (ISCs). Chronic inflammation and tissue damage in the intestine can injure stem cells including accumulation of mutations that may result in ISC dysfunction and transformation. ISCs are a key element in intestinal function and pathology; however, very little is known about the effects of alcohol on ISCs. We hypothesize that dysregulation of ISCs is one mechanism by which alcohol induces long-lasting intestinal damage.

METHODS

In Vivo: Small intestinal samples from alcohol- and control-fed mice were assessed for ISC markers (Lgr5 and Bmi1) and the changes of the β-catenin signaling using immunofluorescent microscopy, Western blotting, and RT-PCR. Ex Vivo: Organoids were generated from small intestine tissue and subsequently exposed to alcohol and analyzed for ISC markers, β-catenin signaling.

RESULTS

Chronic alcohol consumption significantly decreased the expression of stem cell markers, Bmi1 in the small intestine of the alcohol-fed mice and also resulted in dysregulation of the β-catenin signaling-an essential regulator of its target gene Lgr5 and ISC function. Exposure of small intestine-derived organoids to 0.2% alcohol significantly reduced the growth of the organoids, including budding, and total surface area of the organoid cultures. Alcohol also significantly decreased the expression of Lgr5, p-β-catenin (ser552), and Bmi1 in the organoid model.

CONCLUSIONS

Both chronic alcohol feeding and acute exposure of alcohol resulted in ISC dysregulation which might be one mechanism for alcohol-induced long-lasting intestinal damage.

Alcohol and Gut-Derived Inflammation

In large amounts, alcohol and its metabolites can overwhelm the gastrointestinal tract (GI) and liver and lead to damage both within the GI and in other organs. Specifically, alcohol and its metabolites promote intestinal inflammation through multiple pathways. That inflammatory response, in turn, exacerbates alcohol-induced organ damage, creating a vicious cycle and leading to additional deleterious effects of alcohol both locally and systemically. This review summarizes the mechanisms by which chronic alcohol intake leads to intestinal inflammation, including altering intestinal microbiota composition and function, increasing the permeability of the intestinal lining, and affecting the intestinal immune homeostasis. Understanding the mechanisms of alcohol-induced intestinal inflammation can aid in the discovery of therapeutic approaches to mitigate alcohol-induced organ dysfunctions.

The Circadian Clock Mutation Promotes Intestinal Dysbiosis

BACKGROUND

Circadian rhythm disruption is a prevalent feature of modern day society that is associated with an increase in pro-inflammatory diseases, and there is a clear need for a better understanding of the mechanism(s) underlying this phenomenon. We have previously demonstrated that both environmental and genetic circadian rhythm disruption causes intestinal hyperpermeability and exacerbates alcohol-induced intestinal hyperpermeability and liver pathology. The intestinal microbiota can influence intestinal barrier integrity and impact immune system function; thus, in this study, we sought to determine whether genetic alteration of the core circadian clock gene, Clock, altered the intestinal microbiota community.

METHODS

Male Clock(Δ19) -mutant mice (mice homozygous for a dominant-negative-mutant allele) or littermate wild-type mice were fed 1 of 3 experimental diets: (i) a standard chow diet, (ii) an alcohol-containing diet, or (iii) an alcohol-control diet in which the alcohol calories were replaced with dextrose. Stool microbiota was assessed with 16S ribosomal RNA gene amplicon sequencing.

RESULTS

The fecal microbial community of Clock-mutant mice had lower taxonomic diversity, relative to wild-type mice, and the Clock(Δ19) mutation was associated with intestinal dysbiosis when mice were fed either the alcohol-containing or the control diet. We found that alcohol consumption significantly altered the intestinal microbiota in both wild-type and Clock-mutant mice.

CONCLUSIONS

Our data support a model by which circadian rhythm disruption by the Clock(Δ19) mutation perturbs normal intestinal microbial communities, and this trend was exacerbated in the context of a secondary dietary intestinal stressor.

Circadian Rhythm and the Gut Microbiome

Circadian rhythms are 24-h patterns regulating behavior, organs, and cells in living organisms. These rhythms align biological functions with regular and predictable environmental patterns to optimize function and health. Disruption of these rhythms can be detrimental resulting in metabolic syndrome, cancer, or cardiovascular disease, just to name a few. It is now becoming clear that the intestinal microbiome is also regulated by circadian rhythms via intrinsic circadian clocks as well as via the host organism. Microbiota rhythms are regulated by diet and time of feeding which can alter both microbial community structure and metabolic activity which can significantly impact host immune and metabolic function. In this review, we will cover how host circadian rhythms are generated and maintained, how host circadian rhythms can be disrupted, as well as the consequences of circadian rhythm disruption. We will further highlight the newly emerging literature indicating the importance of circadian rhythms of the intestinal microbiota.

Osteoarthritis-like pathologic changes in the knee joint induced by environmental disruption of circadian rhythms is potentiated by a high-fat diet

A variety of environmental factors contribute to progressive development of osteoarthritis (OA). Environmental factors that upset circadian rhythms have been linked to various diseases. Our recent work establishes chronic environmental circadian disruption - analogous to rotating shiftwork-associated disruption of circadian rhythms in humans - as a novel risk factor for the development of OA. Evidence suggests shift workers are prone to obesity and also show altered eating habits (i.e., increased preference for high-fat containing food). In the present study, we investigated the impact of chronic circadian rhythm disruption in combination with a high-fat diet (HFD) on progression of OA in a mouse model. Our study demonstrates that when mice with chronically circadian rhythms were fed a HFD, there was a significant proteoglycan (PG) loss and fibrillation in knee joint as well as increased activation of the expression of the catabolic mediators involved in cartilage homeostasis. Our results, for the first time, provide the evidence that environmental disruption of circadian rhythms plus HFD potentiate OA-like pathological changes in the mouse joints. Thus, our findings may open new perspectives on the interactions of chronic circadian rhythms disruption with diet in the development of OA and may have potential clinical implications.

Chronic Alcohol Exposure and the Circadian Clock Mutation Exert Tissue-Specific Effects on Gene Expression in Mouse Hippocampus, Liver, and Proximal Colon

BACKGROUND

Chronic alcohol exposure exerts numerous adverse effects, although the specific mechanisms underlying these negative effects on different tissues are not completely understood. Alcohol also affects core properties of the circadian clock system, and it has been shown that disruption of circadian rhythms confers vulnerability to alcohol-induced pathology of the gastrointestinal barrier and liver. Despite these findings, little is known of the molecular interactions between alcohol and the circadian clock system, especially regarding implications for tissue-specific susceptibility to alcohol pathologies. The aim of this study was to identify changes in expression of genes relevant to alcohol pathologies and circadian clock function in different tissues in response to chronic alcohol intake.

METHODS

Wild-type and circadian Clock(Δ19) mutant mice were subjected to a 10-week chronic alcohol protocol, after which hippocampal, liver, and proximal colon tissues were harvested for gene expression analysis using a custom-designed multiplex magnetic bead hybridization assay that provided quantitative assessment of 80 mRNA targets of interest, including 5 housekeeping genes and a predetermined set of 75 genes relevant for alcohol pathology and circadian clock function.

RESULTS

Significant alterations in expression levels attributable to genotype, alcohol, and/or a genotype by alcohol interaction were observed in all 3 tissues, with distinct patterns of expression changes observed in each. Of particular interest was the finding that a high proportion of genes involved in inflammation and metabolism on the array was significantly affected by alcohol and the Clock(Δ19) mutation in the hippocampus, suggesting a suite of molecular changes that may contribute to pathological change.

CONCLUSIONS

These results reveal the tissue-specific nature of gene expression responses to chronic alcohol exposure and the Clock(Δ19) mutation and identify specific expression profiles that may contribute to tissue-specific vulnerability to alcohol-induced injury in the brain, colon, and liver.

Abnormal lipopolysaccharide binding protein as marker of gastrointestinal inflammation in Parkinson disease

Objective: An inflammation-driven model of PD has been proposed based on the endotoxin lipopolysaccaride (LPS), a potential source of inflammation in the gastrointestinal system linked to neurotoxicity. Systemic exposure to bacterial endotoxin (LPS) can be determined by measuring plasma LPS binding protein (LBP). We aimed to evaluate whether lipopolysaccharide binding protein (LBP) can be used to distinguish PD subjects from control subjects and to assess whether LBP levels correlate with PD disease severity.

Methods: We measured plasma LBP (ng/ml) using an ELISA kit in 94 PD subjects of various stages and 97 control subjects. Disease severity was assessed using the UPDRS and Hoehn and Yahr staging. The LBP level between the PD and control groups was compared using analysis of covariance. Spearman correlation was used to explore the relationship between LBP level and disease severity.

Results: The mean LBP level in PD subjects (n = 94) was significantly different from control subjects (n = 95, p = 0.018). In PD subjects, we did not find a correlation between mean LBP level and disease severity.

Conclusions: Our data suggests that LBP is one GI biomarker related to LPS induced neurotoxicity. However, there was significant variability in LBP levels within the PD and control groups, limiting its utility as a stand-alone biomarker. This study supports the role of LPS induced neurotoxicity in PD and further exploration of this pathway may be useful in developing sensitive and specific biomarkers for PD.

Environmental disruption of circadian rhythm predisposes mice to osteoarthritis-like changes in knee joint

Circadian rhythm dysfunction is linked to many diseases, yet pathophysiological roles in articular cartilage homeostasis and degenerative joint disease including osteoarthritis (OA) remains to be investigated in vivo. Here, we tested whether environmental or genetic disruption of circadian homeostasis predisposes to OA-like pathological changes. Male mice were examined for circadian locomotor activity upon changes in the light:dark (LD) cycle or genetic disruption of circadian rhythms. Wild-type (WT) mice were maintained on a constant 12 h:12 h LD cycle (12:12 LD) or exposed to weekly 12 h phase shifts. Alternatively, male circadian mutant mice (Clock(Δ19) or Csnk1e(tau) mutants) were compared with age-matched WT littermates that were maintained on a constant 12:12 LD cycle. Disruption of circadian rhythms promoted osteoarthritic changes by suppressing proteoglycan accumulation, upregulating matrix-degrading enzymes and downregulating anabolic mediators in the mouse knee joint. Mechanistically, these effects involved activation of the PKCδ-ERK-RUNX2/NFκB and β-catenin signaling pathways, stimulation of MMP-13 and ADAMTS-5, as well as suppression of the anabolic mediators SOX9 and TIMP-3 in articular chondrocytes of phase-shifted mice. Genetic disruption of circadian homeostasis does not predispose to OA-like pathological changes in joints. Our results, for the first time, provide compelling in vivo evidence that environmental disruption of circadian rhythms is a risk factor for the development of OA-like pathological changes in the mouse knee joint.

The Role of miR-212 and iNOS in Alcohol-Induced Intestinal Barrier Dysfunction and Steatohepatitis

BACKGROUND

Alcoholic liver disease is commonly associated with intestinal barrier dysfunction. Alcohol-induced dysregulation of intestinal tight junction proteins, such as Zonula Occludens-1 (ZO-1), plays an important role in alcohol-induced gut leakiness. However, the mechanism of alcohol-induced disruption of tight junction proteins is not well established. The goal of this study was to elucidate this mechanism by studying the role of microRNA 212 (miR-212) and inducible nitric oxide synthase (iNOS) in alcohol-induced gut leakiness.

METHODS

The permeability of the Caco-2 monolayer was assessed by transepithelial electrical resistance and flux of fluorescein sulfonic acid. miR-212 was measured by real-time polymerase chain reaction. The wild-type, iNOS knockout, and miR-212 knockdown mice were fed with alcohol diet (29% of total calories, 4.5% v/v) for 8 weeks. The LNA-anti-miR-212 was used to inhibit miR-212 expression in mice. The alcohol-induced intestinal permeability, miR-212 expression, and liver injuries in mice were measured.

RESULTS

Our in vitro monolayer and in vivo mice studies showed that: (i) alcohol-induced overexpression of the intestinal miR-212 and intestinal hyperpermeability is prevented using miR-212 knockdown techniques; and (ii) iNOS is up-regulated in the intestine by alcohol and that iNOS signaling is required for alcohol-induced miR-212 overexpression, ZO-1 disruption, gut leakiness, and steatohepatitis.

CONCLUSIONS

These studies thus support a novel miR-212 mechanism for alcohol-induced gut leakiness and a potential target that could be exploited for therapeutic intervention to prevent leaky gut and liver injury in alcoholics.

Colonic bacterial composition in Parkinson's disease

INTRODUCTION

We showed that Parkinson's disease (PD) patients have alpha-synuclein (α-Syn) aggregation in their colon with evidence of colonic inflammation. If PD patients have altered colonic microbiota, dysbiosis might be the mechanism of neuroinflammation that leads to α-Syn misfolding and PD pathology.

METHODS

Sixty-six sigmoid mucosal biopsies and 65 fecal samples were collected from 38 PD patients and 34 healthy controls. Mucosal-associated and feces microbiota compositions were characterized using high-throughput ribosomal RNA gene amplicon sequencing. Data were correlated with clinical measures of PD, and a predictive assessment of microbial community functional potential was used to identify microbial functions.

RESULTS

The mucosal and fecal microbial community of PD patients was significantly different than control subjects, with the fecal samples showing more marked differences than the sigmoid mucosa. At the taxonomic level of genus, putative, "anti-inflammatory" butyrate-producing bacteria from the genera Blautia, Coprococcus, and Roseburia were significantly more abundant in feces of controls than PD patients. Bacteria from the genus Faecalibacterium were significantly more abundant in the mucosa of controls than PD. Putative, "proinflammatory" Proteobacteria of the genus Ralstonia were significantly more abundant in mucosa of PD than controls. Predictive metagenomics indicated that a large number of genes involved in metabolism were significantly lower in the PD fecal microbiome, whereas genes involved in lipopolysaccharide biosynthesis and type III bacterial secretion systems were significantly higher in PD patients.

CONCLUSION

This report provides evidence that proinflammatory dysbiosis is present in PD patients and could trigger inflammation-induced misfolding of α-Syn and development of PD pathology.

Circadian rhythms, alcohol and gut interactions

The circadian clock establishes rhythms throughout the body with an approximately 24 hour period that affect expression of hundreds of genes. Epidemiological data reveal chronic circadian misalignment, common in our society, significantly increases the risk for a myriad of diseases, including cardiovascular disease, diabetes, cancer, infertility and gastrointestinal disease. Disruption of intestinal barrier function, also known as gut leakiness, is especially important in alcoholic liver disease (ALD). Several studies have shown that alcohol causes ALD in only a 20-30% subset of alcoholics. Thus, a better understanding is needed of why only a subset of alcoholics develops ALD. Compelling evidence shows that increased gut leakiness to microbial products and especially LPS play a critical role in the pathogenesis of ALD. Clock and other circadian clock genes have been shown to regulate lipid transport, motility and other gut functions. We hypothesized that one possible mechanism for alcohol-induced intestinal hyperpermeability is through disruption of central or peripheral (intestinal) circadian regulation. In support of this hypothesis, our recent data shows that disruption of circadian rhythms makes the gut more susceptible to injury. Our in vitro data show that alcohol stimulates increased Clock and Per2 circadian clock proteins and that siRNA knockdown of these proteins prevents alcohol-induced permeability. We also show that intestinal Cyp2e1-mediated oxidative stress is required for alcohol-induced upregulation of Clock and Per2 and intestinal hyperpermeability. Our mouse model of chronic alcohol feeding shows that circadian disruption through genetics (in Clock(▵19) mice) or environmental disruption by weekly 12h phase shifting results in gut leakiness alone and exacerbates alcohol-induced gut leakiness and liver pathology. Our data in human alcoholics show they exhibit abnormal melatonin profiles characteristic of circadian disruption. Taken together our data support circadian mechanisms for alcohol-induced gut leakiness that could provide new therapeutic targets for ALD.