Cognitive stimulation and psychosocial results in older adults: A systematic review and meta-analysis.

INTRODUCTION: Cognitive stimulation (CS) is a popular and cost-effective intervention, which applies different types of techniques focused on cognitive skills and can be administered by different professionals. CS can be defined as activities that involve cognitive processing usually conducted in a social context and often in a group. Therefore, CS can improve psychosocial functioning and quality of life (QoL), depression, anxiety and activities of daily living (ADLs) independent of the pharmacological treatment such as acetylcholinesterase inhibitors. The objective of this systematic review and meta-analysis was to evaluate the effects of CS on psychosocial outcomes in older adults (aged 65 years or over), with healthy cognitive ageing, mild cognitive impairment (MCI), and dementia. METHODS: PubMed, Scopus and Web of Science databases were examined from inception to October 2021. A total of 1,997 studies were initially identified in these databases. After discarding studies that did not meet the inclusion criteria, 30 studies were finally included in the systematic review and the meta-analysis performed with robust variance estimator (RVE) due the inclusion of studies with repeated measurements. The quality assessment tools from the National Institutes of Health were used to evaluate the quality of the studies. RESULTS: CS was significantly associated with a higher QoL in participants who received personalized/adapted CS (RVE = 0.11±0.19 [-0.76, 0.99], t(1.86) = 0.6, p = 0.61). . CONCLUSION: Personalized/adapted CS seems to improve QoL in older adults.

Gut Microbiota-Derived Short-Chain Fatty Acids: Novel Regulators of Intestinal Serotonin Transporter.

Serotonin (5-HT) is a key neurotransmitter synthesized both in the gut and the central nervous system. It exerts its signaling through specific receptors (5-HTR), which regulate numerous behaviors and functions such as mood, cognitive function, platelet aggregation, gastrointestinal motility, and inflammation. Serotonin activity is determined mainly by the extracellular availability of 5-HT, which is controlled by the serotonin transporter (SERT). Recent studies indicate that, by activation of innate immunity receptors, gut microbiota can modulate serotonergic signaling by SERT modulation. As part of its function, gut microbiota metabolize nutrients from diet to produce different by-products, including short-chain fatty acids (SCFAs): propionate, acetate, and butyrate. However, it is not known whether these SCFAs regulate the serotonergic system. The objective of this study was to analyze the effect of SCFAs on the gastrointestinal serotonergic system using the Caco-2/TC7 cell line that expresses SERT and several receptors constitutively. Cells were treated with different SCFAs concentrations, and SERT function and expression were evaluated. In addition, the expression of 5-HT receptors 1A, 2A, 2B, 3A, 4, and 7 was also studied. Our results show that the microbiota-derived SCFAs regulate intestinal serotonergic system, both individually and in combination, modulating the function and expression of SERT and the 5-HT1A, 5-HT2B, and 5-HT7 receptors expression. Our data highlight the role of gut microbiota in the modulation of intestinal homeostasis and suggest microbiome modulation as a potential therapeutic treatment for intestinal pathologies and neuropsychiatric disorders involving serotonin.

Cognitive stimulation and cognitive results in older adults: A systematic review and meta-analysis.

BACKGROUND AND PURPOSE: The lack of cognitive activity accelerates age cognitive decline. Cognitive stimulation (CS) tries to enhance cognitive functioning. The purpose of this systematic review and meta-analysis was to evaluate the effects of CS on cognitive outcomes (general cognitive functioning and specific cognitive domains) in older adults (aged 65 years or older, cognitively healthy participants, or with mild cognitive impairment, or dementia). METHODS: PubMed, Scopus and Web of Science databases were examined from inception to October 2021. A total of 1,997 studies were identified in these databases, and. 33 studies were finally included in the systematic review and the meta-analysis. Raw means and standard deviations were used for continuous outcomes. Publication bias was examined by Egger's Regression Test for Funnel Plot Asymmetry and the quality assessment tools from the National Institutes of Health. RESULTS: CS significantly improves general cognitive functioning (mean difference=MD = 1.536, 95%CI, 0.832 to 2.240), memory (MD = 0.365, 95%CI, 0.300 to 0.430), orientation (MD = 0.428, 95%CI, 0.306 to 0.550), praxis (MD = 0.278, 95%CI, 0.094 to 0.462) and calculation (MD = 0.228, 95%CI, 0.112 to 0.343). CONCLUSION: CS seems to increase general cognitive functioning, memory, orientation, praxis, and calculation in older adults.

Job Demands May Determine Cognitive and Physical Aging After Retirement.

During adulthood, we spend most of our time and efforts at work. However, the impact of employment in aging is poorly explored. Our study addressed how job demands can affect aging after retirement. We have developed a descriptive observational study carried out in 367 older adults with a mean age of 73.9 years (66.5% women and 33.5% men), measuring cognition and functional status. Our results demonstrate that older adults who had high mental demands in their jobs, show better scores in cognition. However, they show poor functional development of basic and instrumental activities of daily life (p< .05). In contrast, former workers who had high physical demands, display lower scores in cognition and lower functional performance in instrumental activities (p< .05). Work life activities contribute to cognitive and physical decline after retirement. Therefore, healthy aging should include interventions that consider the job influence on the age impairment.

Intestinal serotonergic system is modulated by Toll-like receptor 9

Intestinal serotonergic system is a key modulator of intestinal homeostasis; however, its regulation is still unclear. Toll-like receptor 9 (TLR9), an innate immune receptor, detects different external agents in the intestine, preserving intestinal integrity. Since little is known about TLR9 role in the intestine, our aim was to address the potential regulation between TLR9 and intestinal serotonergic system. Caco-2/TC7 cell line and intestinal tract of Tlr9−/− mice were used in this study. Serotonin uptake studies were performed, and molecular expression of different serotonergic components was analyzed by western blot and real-time PCR. Our results show that TLR9 activation inhibits serotonin transporter activity and expression, involving p38/MAPK and ERK/MAPK intracellular pathways, and reciprocally, serotonin increases TLR9 expression. Supporting this interaction, serotonin transporter, serotonin receptors and serotonin producer enzymes were found altered in intestinal tract of Tlr9−/− mice. We conclude that TLR9 could contribute to intestinal homeostasis by modulation of intestinal serotonergic system. (AU)

Effects of multi-component non-pharmacological interventions on cognition in participants with mild cognitive impairment: A systematic review and meta-analysis.

BACKGROUND AND PURPOSE: Mild cognitive impairment (MCI) describes a stage of intermediate cognitive dysfunction where the risk of conversion to dementia is elevated. Given the absence of effective pharmacological treatments for MCI, increasing numbers of studies are attempting to understand how multicomponent non-pharmacological interventions (MNPI) could benefit MCI. The purpose of this systematic review and meta-analysis were to assess the effects of two-component MNPI (simultaneous cognitive intervention based on cognitive stimulation, cognitive training and/or cognitive rehabilitation or combined cognitive and physical interventions) on global cognition and cognitive functions in older adults with MCI and to compare the degree of efficacy between the two interventions. METHODS: After searching electronic databases (PubMed, Web of Science, Scopus and Cochrane Central) for randomized controlled trials and clinical trials published from 2010 to 18 January 2021, 562 studies were found. 8 studies were included in this review, with a fair to good quality according to the PEDro scale. RESULTS: From a random-effects model meta-analysis, the pooled standardized MMSE mean difference between the intervention and control groups showed a significant small-to-medium effect in global cognition in MMSE score (0.249; 95% CI = [0.067, 0.431]), which seemed to be greater for combined physical and cognitive interventions. However, the meta-analyses did not show any effects regarding specific cognitive functions. CONCLUSION: Our analyses support that MNPI could improve the global cognition in older adults with MCI. However, more studies are needed to analyze the potential benefits of MNPI on older adults with MCI.

Intestinal serotonergic system is modulated by Toll-like receptor 9.

Intestinal serotonergic system is a key modulator of intestinal homeostasis; however, its regulation is still unclear. Toll-like receptor 9 (TLR9), an innate immune receptor, detects different external agents in the intestine, preserving intestinal integrity. Since little is known about TLR9 role in the intestine, our aim was to address the potential regulation between TLR9 and intestinal serotonergic system. Caco-2/TC7 cell line and intestinal tract of Tlr9-/- mice were used in this study. Serotonin uptake studies were performed, and molecular expression of different serotonergic components was analyzed by western blot and real-time PCR. Our results show that TLR9 activation inhibits serotonin transporter activity and expression, involving p38/MAPK and ERK/MAPK intracellular pathways, and reciprocally, serotonin increases TLR9 expression. Supporting this interaction, serotonin transporter, serotonin receptors and serotonin producer enzymes were found altered in intestinal tract of Tlr9-/- mice. We conclude that TLR9 could contribute to intestinal homeostasis by modulation of intestinal serotonergic system.

Special Issue "Clinical Advances in Chronic Intestinal Diseases Treatment".

During the last decades, the management of patients with chronic intestinal diseases has experienced remarkable progress from both diagnostic and therapeutic point of view [...].

Toll-like receptors: New targets for multiple myeloma treatment?

Despite recent biomedical improvements in treating multiple myeloma, this disease still remains incurable. Toll-like receptors (TLRs) are key immune receptors that recognize conserved molecular patterns expressed by pathogens and damaged cells. Activation of TLRs can induce several effects including inflammatory responses, modulation of cell cycle, apoptosis, or regulation of cell metabolism. In multiple myeloma there is a dysregulated signalling of TLRs due to an abnormal presence of certain pathogens and release of molecules from damaged cells. Thus, TLRs could be critical players for tumour microenvironment and multiple myeloma progression. This haematological malignancy is characterized by a high percentage of recurrences, where many patients can develop residual drug-resistant malignant cells. Strategic targeting of TLRs might result in novel therapeutic combinations that improve the response to current treatments, reducing relapses. This review examines the potential of TLRs as targets for the treatment of multiple myeloma, making a particular emphasis on their therapeutic applications.

Crosstalk Between Intestinal Serotonergic System and Pattern Recognition Receptors on the Microbiota-Gut-Brain Axis.

Disruption of the microbiota-gut-brain axis results in a wide range of pathologies that are affected, from the brain to the intestine. Gut hormones released by enteroendocrine cells to the gastrointestinal (GI) tract are important signaling molecules within this axis. In the search for the language that allows microbiota to communicate with the gut and the brain, serotonin seems to be the most important mediator. In recent years, serotonin has emerged as a key neurotransmitter in the gut-brain axis because it largely contributes to both GI and brain physiology. In addition, intestinal microbiota are crucial in serotonin signaling, which gives more relevance to the role of the serotonin as an important mediator in microbiota-host interactions. Despite the numerous investigations focused on the gut-brain axis and the pathologies associated, little is known regarding how serotonin can mediate in the microbiota-gut-brain axis. In this review, we will mainly discuss serotonergic system modulation by microbiota as a pathway of communication between intestinal microbes and the body on the microbiota-gut-brain axis, and we explore novel therapeutic approaches for GI diseases and mental disorders.

Neurotransmitter Dysfunction in Irritable Bowel Syndrome: Emerging Approaches for Management.

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder whose aetiology is still unknown. Most hypotheses point out the gut-brain axis as a key factor for IBS. The axis is composed of different anatomic and functional structures intercommunicated through neurotransmitters. However, the implications of key neurotransmitters such as norepinephrine, serotonin, glutamate, GABA or acetylcholine in IBS are poorly studied. The aim of this review is to evaluate the current evidence about neurotransmitter dysfunction in IBS and explore the potential therapeutic approaches. IBS patients with altered colorectal motility show augmented norepinephrine and acetylcholine levels in plasma and an increased sensitivity of central serotonin receptors. A decrease of colonic mucosal serotonin transporter and a downregulation of α2 adrenoceptors are also correlated with visceral hypersensitivity and an increase of 5-hydroxyindole acetic acid levels, enhanced expression of high affinity choline transporter and lower levels of GABA. Given these neurotransmitter dysfunctions, novel pharmacological approaches such as 5-HT3 receptor antagonists and 5-HT4 receptor agonists are being explored for IBS management, for their antiemetic and prokinetic effects. GABA-analogous medications are being considered to reduce visceral pain. Moreover, agonists and antagonists of muscarinic receptors are under clinical trials. Targeting neurotransmitter dysfunction could provide promising new approaches for IBS management.

Comparative effect of bovine buttermilk, whey, and lactoferrin on the innate immunity receptors and oxidative status of intestinal epithelial cells.

Milk contains bioactive molecules with important functions as defensive proteins; among them are the whey protein lactoferrin and proteins of the milk fat globule membrane (MFGM) present in buttermilk. The aim of this study has been to investigate the effects of lactoferrin, whey, and buttermilk as modulators of intestinal innate immunity and oxidative stress on intestinal epithelial cells, to evaluate its potential use for the development of functional foods. The mRNA expression levels of innate immune system Toll-like receptors (TLR2, TLR4, and TLR9), lipid peroxidation (malondialdehyde + 4-hydroxyalkenals) and protein expression levels of carbonyl were analyzed in enterocyte-like Caco-2/TC7 cells treated for 24 h with different concentrations of lactoferrin, whey, or buttermilk. None of the substances analyzed caused oxidative damage; however, whey significantly decreased the levels of lipid peroxidation. Furthermore, both lactoferrin and whey reduced the oxidative stress induced by lipopolysaccharide. With respect to TLR receptors, lactoferrin, whey, and buttermilk specifically altered the expression of TLR2, TLR4, and TLR9 receptors, with a strong decrease in the expression levels of TLR4. These results suggest that lactoferrin, whey, and buttermilk are potentially interesting ingredients for functional foods because they seem to modulate oxidative stress and the inflammatory response induced by the activation of TLRs.

Oxidized phospholipids affect small intestine neuromuscular transmission and serotonergic pathways in juvenile mice.

BACKGROUND: Oxidized phospholipid derivatives (OxPAPCs) act as bacterial lipopolysaccharide (LPS)-like damage-associated molecular patterns. OxPAPCs dose-dependently exert pro- or anti-inflammatory effects by interacting with several cellular receptors, mainly Toll-like receptors 2 and 4. It is currently unknown whether OxPAPCs may affect enteric nervous system (ENS) functional and structural integrity. METHODS: Juvenile (3 weeks old) male C57Bl/6 mice were treated intraperitoneally with OxPAPCs, twice daily for 3 days. Changes in small intestinal contractility were evaluated by isometric neuromuscular responses to receptor and non-receptor-mediated stimuli. Alterations in ENS integrity and serotonergic pathways were assessed by real-time PCR and confocal immunofluorescence microscopy in longitudinal muscle-myenteric plexus whole-mount preparations (LMMPs). Tissue levels of serotonin (5-HT), tryptophan, and kynurenine were measured by HPLC coupled to UV/fluorescent detection. KEY RESULTS: OxPAPC treatment induced enteric gliosis, loss of myenteric plexus neurons, and excitatory hypercontractility, and reduced nitrergic neurotransmission with no changes in nNOS+ neurons. Interestingly, these changes were associated with a higher functional response to 5-HT, altered immunoreactivity of 5-HT receptors and serotonin transporter (SERT) together with a marked decrease in 5-HT levels, shifting tryptophan metabolism toward kynurenine production. CONCLUSIONS AND INFERENCES: OxPAPC treatment disrupted structural and functional integrity of the ENS, affecting serotoninergic tone and 5-HT tissue levels toward a higher kynurenine content during adolescence, suggesting that changes in intestinal lipid metabolism toward oxidation can affect serotoninergic pathways, potentially increasing the risk of developing functional gastrointestinal disorders during critical stages of development.

Astrocyte senescence may drive alterations in GFAPα, CDKN2A p14ARF, and TAU3 transcript expression and contribute to cognitive decline.

The accumulation of senescent cells in tissues is causally linked to the development of several age-related diseases; the removal of senescent glial cells in animal models prevents Tau accumulation and cognitive decline. Senescent cells can arise through several distinct mechanisms; one such mechanism is dysregulation of alternative splicing. In this study, we characterised the senescent cell phenotype in primary human astrocytes in terms of SA-ß-Gal staining and SASP secretion, and then assessed splicing factor expression and candidate gene splicing patterns. Finally, we assessed associations between expression of dysregulated isoforms and premature cognitive decline in 197 samples from the InCHIANTI study of ageing, where expression was present in both blood and brain. We demonstrate here that senescent astrocytes secrete a modified SASP characterised by increased IL8, MMP3, MMP10, and TIMP2 but decreased IL10 levels. We identified significant changes in splicing factor expression for 10/20 splicing factors tested in senescent astrocytes compared with early passage cells, as well as dysregulation of isoform levels for 8/13 brain or senescence genes tested. Finally, associations were identified between peripheral blood GFAPα, TAU3, and CDKN2A (P14ARF) isoform levels and mild or severe cognitive decline over a 3-7-year period. Our data are suggestive that some of the features of cognitive decline may arise from dysregulated splicing of important genes in senescent brain support cells, and that defects in alternative splicing or splicing regulator expression deserve exploration as points of therapeutic intervention in the future.

A dynamical systems model for the measurement of cellular senescence.

Senescent cells provide a good in vitro model to study ageing. However, cultures of 'senescent' cells consist of a mix of cell subtypes (proliferative, senescent, growth-arrested and apoptotic). Determining the proportion of senescent cells is crucial for studying ageing and developing new anti-degenerative therapies. Commonly used markers such as doubling population, senescence-associated ß-galactosidase, Ki-67, γH2AX and TUNEL assays capture diverse and overlapping cellular populations and are not purely specific to senescence. A newly developed dynamical systems model follows the transition of an initial culture to senescence tracking population doubling, and the proportion of cells in proliferating, growth-arrested, apoptotic and senescent states. Our model provides a parsimonious description of transitions between these states accruing towards a predominantly senescent population. Using a genetic algorithm, these model parameters are well constrained by an in vitro human primary fibroblast dataset recording five markers at 16 time points. The computational model accurately fits to the data and translates these joint markers into the first complete description of the proportion of cells in different states over the lifetime. The high temporal resolution of the dataset demonstrates the efficacy of strategies for reconstructing the trajectory towards replicative senescence with a minimal number of experimental recordings.

Alternative splicing in serotonergic system: Implications in neuropsychiatric disorders.

BACKGROUND: The serotonergic system is a key component of physiological brain function and is essential for proper neurological activity. Numerous neuropsychiatric disorders are associated with deregulation of the serotonergic system. Accordingly, many pharmacological treatments are focused on modulation of this system. While providing a promising line of therapeutic moderation, these approaches may be complicated due to the presence of alternative splicing events for key genes in this pathway. Alternative splicing is a co-transcriptional process by which different mRNA transcripts can be produced from the same gene. These different isoforms may have diverse activities and functions, and their relative balance is often critical for the maintenance of homeostasis. Alternative splicing greatly increases the production of proteins, augmenting cell plasticity, and provides an important control point for regulation of gene expression. AIM: The objective of this narrative review is to discuss the potential impact of alternative splicing of different components of the serotonergic system and speculate on their involvement in several neuropsychiatric disorders. CONCLUSIONS: The specific role of each isoform in disease and their relative activities in the signalling pathways involved are yet to be determined. We need to gain a better understanding of the basis of alternative isoforms of the serotonergic system in order to fully understand their impact and be able to develop new effective pharmacological isoform-specific targets.

TLR2 and TLR4 interact with sulfide system in the modulation of mouse colonic motility.

BACKGROUND: H2 S is a neuromodulator that may inhibit intestinal motility. H2 S production in colon is yielded by cystathionine ß-synthase (CBS) and cystathionine γ-lyase (CSE) enzymes and sulfate-reducing bacteria (SRB). Toll-like receptors (TLRs) recognize intestinal microbiota. The aim of this work was to evaluate the influence of TLR2 and TLR4 on the endogenous and SRB-mediated synthesis of H2 S and its consequences on the colonic motility of mouse. METHODS: Muscle contractility studies were performed in colon from WT, Tlr2-/- , and Tlr4-/- mice. The mRNA levels of TLR2, TLR4, CBS, CSE, and SRB were measured by real-time PCR. Free sulfide levels in colon and feces were determined by colorimetric assays. RESULTS: NaHS and GYY4137, donors of H2 S, reduced the contractility of colon. Aminooxyacetic acid (AOAA), inhibitor of CBS, and D-L propargylglycine (PAG), inhibitor of CSE, increased the contractility of colon. In vivo treatment with NaHS or GYY4137 inhibited the spontaneous contractions and upregulated TLR2 expression. The in vivo activation of TLR4 with lipopolysaccharide increased the contractile response to PAG, mRNA levels of CSE, and the free sulfide levels of H2 S in colon. In Tlr2-/- and Tlr4-/-  mice, the contractions induced by AOAA and PAG and mRNA levels of CBS and CSE were lower with respect to WT mice. Deficiency of TLR2 or TLR4 provokes alterations in free sulfide levels and SRB of colon. CONCLUSIONS AND INFERENCES: Our study demonstrates interaction between TLR2 and TLR4 and the sulfide system in the regulation of colonic motility and contributes to the pathophysiology knowledge of intestinal motility disorders.

FOXO1 and ETV6 genes may represent novel regulators of splicing factor expression in cellular senescence.

Cellular plasticity is a key facet of cellular homeostasis requiring correct temporal and spatial patterns of alternative splicing. Splicing factors, which orchestrate this process, demonstrate age-related dysregulation of expression; they are emerging as potential influences on aging and longevity. The upstream drivers of these alterations are still unclear but may involve aberrant cellular signaling. We compared the phosphorylation status of proteins in multiple signaling pathways in early and late passage human primary fibroblasts. We then assessed the impact of chemical inhibition or targeted knockdown of direct downstream targets of the ERK and AKT pathways on splicing factor expression, cellular senescence, and proliferation kinetics in senescent primary human fibroblasts. Components of the ERK and AKT signaling pathways demonstrated altered activation during cellular aging. Inhibition of AKT and ERK pathways led to up-regulation of splicing factor expression, reduction in senescent cell load, and partial reversal of multiple cellular senescence phenotypes in a dose-dependent manner. Furthermore, targeted knockdown of the genes encoding the downstream targets FOXO1 or ETV6 was sufficient to mimic these observations. Our results suggest that age-associated dysregulation of splicing factor expression and cellular senescence may derive in part from altered activity of ERK and AKT signaling and may act in part through the ETV6 and FOXO1 transcription factors. Targeting the activity of downstream effectors of ERK and AKT may therefore represent promising targets for future therapeutic intervention.-Latorre, E., Ostler, E. L., Faragher, R. G. A., Harries, L. W. FOXO1 and ETV6 genes may represent novel regulators of splicing factor expression in cellular senescence.

Mitochondria-targeted hydrogen sulfide attenuates endothelial senescence by selective induction of splicing factors HNRNPD and SRSF2.

Cellular senescence is a key driver of ageing, influenced by age-related changes to the regulation of alternative splicing. Hydrogen sulfide (H2S) has similarly been described to influence senescence, but the pathways by which it accomplishes this are unclear.We assessed the effects of the slow release H2S donor Na-GYY4137 (100 µg/ml), and three novel mitochondria-targeted H2S donors AP39, AP123 and RT01 (10 ng/ml) on splicing factor expression, cell proliferation, apoptosis, DNA replication, DNA damage, telomere length and senescence-related secretory complex (SASP) expression in senescent primary human endothelial cells.All H2S donors produced up to a 50% drop in senescent cell load assessed at the biochemical and molecular level. Some changes were noted in the composition of senescence-related secretory complex (SASP); IL8 levels increased by 24% but proliferation was not re-established in the culture as a whole. Telomere length, apoptotic index and the extent of DNA damage were unaffected. Differential effects on splicing factor expression were observed depending on the intracellular targeting of the H2S donors. Na-GYY4137 produced a general 1.9 - 3.2-fold upregulation of splicing factor expression, whereas the mitochondria-targeted donors produced a specific 2.5 and 3.1-fold upregulation of SRSF2 and HNRNPD splicing factors only. Knockdown of SRSF2 or HNRNPD genes in treated cells rendered the cells non-responsive to H2S, and increased levels of senescence by up to 25% in untreated cells.Our data suggest that SRSF2 and HNRNPD may be implicated in endothelial cell senescence, and can be targeted by exogenous H2S. These molecules may have potential as moderators of splicing factor expression and senescence phenotypes.

NOD2 Modulates Serotonin Transporter and Interacts with TLR2 and TLR4 in Intestinal Epithelial Cells.

BACKGROUND/AIMS: Serotonin (5-HT) is a chief modulator of intestinal activity. The effects of 5-HT depend on its extracellular availability, which is mainly controlled by serotonin transporter (SERT), expressed in enterocytes. On the other hand, innate immunity, mediated by Toll-like receptors (TLRs) and nucleotide oligomerization domain (NOD)-like receptors (NLRs), is known to control intestinal microbiota and maintain intestinal homeostasis. The dysregulation of the intestinal serotonergic system and innate immunity has been observed in inflammatory bowel diseases (IBD), the incidence of which has severely increased all over the world. The aim of the present study, therefore, was to analyze the effect of NOD2 on intestinal SERT activity and expression, as well as to study the crosstalk of NOD2 with TLR2 and TLR4. METHODS: Intestinal epithelial cell line Caco-2/TC7 was used to analyze SERT activity and SERT, NOD2, TLR2 and TLR4 molecular expression by real-time PCR and western blotting. Moreover, intestinal tract (ileum and colon) from mice deficient in TLR2, TLR4 or TLR2/4 receptors was used to test the interdependence of NOD2 with these TLR receptors. RESULTS: NOD2 activation inhibits SERT activity in Caco-2/TC7 cells, mainly due to the decrement of SERT molecular expression, with RIP2/RICK being the intracellular pathway involved in this effect. This inhibitory effect on SERT would yield an increment of extracellular 5-HT availability. In this sense, 5-HT strongly inhibits NOD2 expression. In addition, NOD2 showed greater interdependence with TLR2 than with TLR4. Indeed, NOD2 expression significantly increased in both cells treated with TLR2 agonists and the intestinal tract of Tlr2-/- mice. CONCLUSIONS: It may be inferred from our data that NOD2 could play a role in intestinal pathophysiology not only through its inherent innate immune role but also due to its interaction with other receptors as TLR2 and the modulation of the intestinal serotonergic system decreasing SERT activity and expression.