Vitamin D and chronic kidney disease: Insights on lipid metabolism of tubular epithelial cell and macrophages in tubulointerstitial fibrosis

Chronic kidney disease (CKD) has been recognized as a significant global health problem due to being an important contributor to morbidity and mortality. Inflammation is the critical event that leads to CKD development orchestrated by a complex interaction between renal parenchyma and immune cells. Particularly, the crosstalk between tubular epithelial cells (TECs) and macrophages is an example of the critical cell communication in the kidney that drives kidney fibrosis, a pathological feature in CKD. Metabolism dysregulation of TECs and macrophages can be a bridge that connects inflammation and fibrogenesis. Currently, some evidence has reported how cellular lipid disturbances can affect kidney disease and cause tubulointerstitial fibrosis highlighting the importance of investigating potential molecules that can restore metabolic parameters. Vitamin D (VitD) is a hormone naturally produced by mammalian cells in a coordinated manner by the skin, liver, and kidneys. VitD deficiency or insufficiency is prevalent in patients with CKD, and serum levels of VitD are inversely correlated with the degree of kidney inflammation and renal function. Proximal TECs and macrophages produce the active form of VitD, and both express the VitD receptor (VDR) that evidence the importance of this nutrient in regulating their functions. However, whether VitD signaling drives physiological and metabolism improvement of TECs and macrophages during kidney injury is an open issue to be debated. In this review, we brought to light VitD as an important metabolic modulator of lipid metabolism in TECs and macrophages. New scientific approaches targeting VitD e VDR signaling at the cellular metabolic level can provide a better comprehension of its role in renal physiology and CKD progression.

Regulation of the immune system by the insulin receptor in health and disease

The signaling pathways downstream of the insulin receptor (InsR) are some of the most evolutionarily conserved pathways that regulate organism longevity and metabolism. InsR signaling is well characterized in metabolic tissues, such as liver, muscle, and fat, actively orchestrating cellular processes, including growth, survival, and nutrient metabolism. However, cells of the immune system also express the InsR and downstream signaling machinery, and there is increasing appreciation for the involvement of InsR signaling in shaping the immune response. Here, we summarize current understanding of InsR signaling pathways in different immune cell subsets and their impact on cellular metabolism, differentiation, and effector versus regulatory function. We also discuss mechanistic links between altered InsR signaling and immune dysfunction in various disease settings and conditions, with a focus on age related conditions, such as type 2 diabetes, cancer and infection vulnerability.

Peroxisome Proliferator-Activated Receptor Alpha Mediates the Beneficial Effects of Atorvastatin in Experimental Colitis

The current therapeutic options for Inflammatory Bowel Diseases (IBD) are limited. Even using common anti-inflammatory, immunosuppressive or biological therapies, many patients become unresponsive to the treatments, immunosuppressed or unable to restrain secondary infections. Statins are cholesterol-lowering drugs with non-canonical anti-inflammatory properties, whose underlying mechanisms of action still remain poorly understood. Here, we described that in vitro atorvastatin (ATO) treatment was not toxic to splenocytes, constrained cell proliferation and modulated IL-6 and IL-10 production in a dose-dependent manner. Mice exposed to dextran sulfate sodium (DSS) for colitis induction and treated with ATO shifted their immune response from Th17 towards Th2, improved the clinical and histological aspects of intestinal inflammation and reduced the number of circulating leukocytes. Both experimental and in silico analyses revealed that PPAR-α expression is reduced in experimental colitis, which was reversed by ATO treatment. While IBD patients also downregulate PPAR-α expression, the responsiveness to biological therapy relied on the restoration of PPAR-α levels. Indeed, the in vitro and in vivo effects induced by ATO treatment were abrogated in Ppara ^-/- mice or leukocytes. In conclusion, the beneficial effects of ATO in colitis are dependent on PPAR-α, which could also be a potential predictive biomarker of therapy responsiveness in IBD.

Targeting immune cell metabolism in kidney diseases

Insights into the relationship between immunometabolism and inflammation have enabled the targeting of several immunity-mediated inflammatory processes that underlie infectious diseases and cancer or drive transplant rejection, but this field remains largely unexplored in kidney diseases. The kidneys comprise heterogeneous cell populations, contain distinct microenvironments such as areas of hypoxia and hypersalinity, and are responsible for a functional triad of filtration, reabsorption and secretion. These distinctive features create myriad potential metabolic therapeutic targets in the kidney. Immune cells have crucial roles in the maintenance of kidney homeostasis and in the response to kidney injury, and their function is intricately connected to their metabolic properties. Changes in nutrient availability and biomolecules, such as cytokines, growth factors and hormones, initiate cellular signalling events that involve energy-sensing molecules and other metabolism-related proteins to coordinate immune cell differentiation, activation and function. Disruption of homeostasis promptly triggers the metabolic reorganization of kidney immune and non-immune cells, which can promote inflammation and tissue damage. The metabolic differences between kidney and immune cells offer an opportunity to specifically target immunometabolism in the kidney.

Butyrate Protects Mice from Clostridium difficile-Induced Colitis through an HIF-1-Dependent Mechanism

Antibiotic-induced dysbiosis is a key factor predisposing intestinal infection by Clostridium difficile. Here, we show that interventions that restore butyrate intestinal levels mitigate clinical and pathological features of C. difficile-induced colitis. Butyrate has no effect on C. difficile colonization or toxin production. However, it attenuates intestinal inflammation and improves intestinal barrier function in infected mice, as shown by reduced intestinal epithelial permeability and bacterial translocation, effects associated with the increased expression of components of intestinal epithelial cell tight junctions. Activation of the transcription factor HIF-1 in intestinal epithelial cells exerts a protective effect in C. difficile-induced colitis, and it is required for butyrate effects. We conclude that butyrate protects intestinal epithelial cells from damage caused by C. difficile toxins via the stabilization of HIF-1, mitigating local inflammatory response and systemic consequences of the infection.

Mitochondria as central hub of the immune system

Nearly 130 years after the first insights into the existence of mitochondria, new rolesassociated with these organelles continue to emerge. As essential hubs that dictate cell fate, mitochondria integrate cell physiology, signaling pathways and metabolism. Thus, recent research has focused on understanding how these multifaceted functions can be used to improve inflammatory responses and prevent cellular dysfunction. Here, we describe the role of mitochondria on the development and function of immune cells, highlighting metabolic aspects and pointing out some metabolic- independent features of mitochondria that sustain cell function.

Butyrate Attenuates Lung Inflammation by Negatively Modulating Th9 Cells

Th9 cells orchestrate allergic lung inflammation by promoting recruitment and activation of eosinophils and mast cells, and by stimulating epithelial mucus production, which is known to be mainly dependent on IL-9. These cells share developmental pathways with induced regulatory T cells that may determine the generation of one over the other subset. In fact, the FOXP3 transcription factor has been shown to bind il9 locus and repress IL-9 production. The microbiota-derived short-chain fatty acids (SCFAs) butyrate and propionate have been described as FOXP3 inducers and are known to have anti-inflammatory properties. While SCFAs attenuate lung inflammation by inducing regulatory T cells and suppressing Th2 responses, their effects on Th9 cells have not been addressed yet. Therefore, we hypothesized that SCFAs would have a protective role in lung inflammation by negatively modulating differentiation and function of Th9 cells. Our results demonstrated that butyrate is more effective than propionate in promoting FOXP3 expression and IL-9 repression. In addition, propionate was found to negatively impact in vitro differentiation of IL-13-expressing T cells. Butyrate treatment attenuated lung inflammation and mucus production in OVA-challenged mice, which presented lower frequency of lung-infiltrated Th9 cells and eosinophils. Both Th9 cell adoptive transfer and IL-9 treatment restored lung inflammation in butyrate-treated OVA-challenged mice, indicating that the anti-inflammatory effects of butyrate may rely on suppressing Th9-mediated immune responses.

Sirtuins in B lymphocytes metabolism and function

Sirtuins (SIRTs) are NAD⁺-dependent histone deacetylases and play a role in virtually all cell biological processes. As SIRTs functions vary according to their subtypes, they can either activate or inhibit signaling pathways upon different conditions or tissues. Recent studies have focused on metabolic effects performed by SIRTs in several cell types since specific metabolic pathways (e.g., aerobic glycolysis, oxidative phosphorylation, β-oxidation, glutaminolysis) are used to determine the cell fate. However, few efforts have been made to understand the role of SIRTs on B lymphocytes metabolism and function. These cells are associated with humoral immune responses by secreting larger amounts of antibodies after differentiating into antibody-secreting cells. Besides, both the SIRTs and B lymphocytes are potential targets to treat several immune-mediated disorders, including cancer. Here, we provide an outlook of recent studies regarding the role of SIRTs in general cellular metabolism and B lymphocytes functions, pointing out the future perspectives of this field.

Microbial-Based Therapies in the Treatment of Inflammatory Bowel Disease - An Overview of Human Studies

Inflammatory bowel disease (IBD) is a group of multifactorial and inflammatory infirmities comprised of two main entities: Ulcerative colitis (UC) and Crohn’s disease (CD). Classic strategies to treat IBD are focused on decreasing inflammation besides inducing and extending disease remission. However, these approaches have several limitations such as low responsiveness, excessive immunosuppression, and refractoriness. Despite the multifactorial causality of IBD, immune disturbances and intestinal dysbiosis have been suggested as the central players in disease pathogenesis. Hence, therapies aiming at modulating intestinal microbial composition may represent a promising strategy in IBD control. Fecal microbiota transplantation (FMT) and probiotics have been explored as promising candidates to reestablish microbial balance in several immune-mediated diseases such as IBD. These microbial-based therapies have demonstrated the ability to reduce both the dysbiotic environment and production of inflammatory mediators, thus inducing remission, especially in UC. Despite these promising results, there is still no consensus on the relevance of such treatments in IBD as a potential clinical strategy. Thus, this review aims to critically review and describe the use of FMT and probiotics to treat patients with IBD.

Dehydroepiandrosterone (DHEA) restrains intestinal inflammation by rendering leukocytes hyporesponsive and balancing colitogenic inflammatory responses

Dehydroepiandrosterone (DHEA) is a hormone that plays an important role in the modulation of inflammatory responses. However, the precise mechanisms that link the actions of this androgen with protection or susceptibility to inflammatory bowel diseases (IBD) remain uknown. Here we showed that low dose DHEA inhibited proliferation of spleen cells and IFN-у production. The hormone was not toxic to myeloid lineage cells, although it caused necrosis of spleen cells at the intermediate and highest doses in vitro (50 and 100μM). The treatment of C57BL/6 mice with DHEA during colitis induction by dextran sodium sulfate (DSS) led to a reduction in weight loss and clinical signs of disease. There were decreased peripheral blood monocytes on day 6 of DSS exposure and treatment, besides increase in circulating neutrophils in the tissue repair phase. DHEA also led to reduced lamina propria cellularity and restoration of normal colon length. These results were accompanied by decreased expression of IL-6 and TGF-β mRNA, while IL-13 was augmented in the colon on day 6, which was probably related to attenuation of inflammation. There was retention of CD4(+) cells in the spleen after use of DHEA, along with augmented frequency of CD4(+)IL-4(+) cells, decreased CD4(+)IFN-ɣ(+) in spleen and constrained CD4(+)IL-17(+) population in the mesenteric lymph nodes. Moreover, splenocytes of mice treated with DHEA became hyporesponsive, as observed by reduced proliferation after re-stimulation ex-vivo. In conclusion, DHEA modifyies leukocyte activity and balances the exacerbated immune responses which drive local and systemic damages in IBD.

Aedes aegypti salivary gland extract ameliorates experimental inflammatory bowel disease

Current therapies for inflammatory bowel disease (IBD) are not totally effective, resulting in persistent and recurrent disease for many patients. Mosquito saliva contains immunomodulatory molecules and therein could represent a novel therapy for IBD. Here, we demonstrated the therapeutic activity of salivary gland extract (SGE) of Aedes aegypti on dextran sulfate sodium (DSS)-induced colitis. For this purpose, C57BL/6 male mice were exposed to 3% DSS in drinking water and treated with SGE at early (days 3-5) or late (days 5-8) time points, followed by euthanasia on days 6 and 9, respectively, for sample collection. The results showed an improvement in clinical disease outcome and postmortem scores after SGE treatment, accompanied by the systemic reduction in peripheral blood lymphocytes, with no impact on bone marrow and mesenteric lymph nodes cellularity or macrophages toxicity. Moreover, a local diminishment of IFN-γ, TNF-α, IL-1β and IL-5 cytokines together with a reduction in the inflammatory area were observed in the colon of SGE-treated mice. Strikingly, early treatment with SGE led to mice protection from a late DSS re-challenging, as observed by decreased clinical and postmortem scores, besides reduced circulating lymphocytes, indicating that the mosquito saliva may present components able to prevent disease relapse. Indeed, high performance liquid chromatography (HPLC) experiments pointed to a major SGE pool fraction (F3) able to ameliorate disease signs. In conclusion, SGE and its components might represent a source of important immunomodulatory molecules with promising therapeutic activity for IBD.

Classical and recent advances in the treatment of inflammatory bowel diseases

Crohn's disease (CD) and ulcerative colitis (UC) are intestinal disorders that comprise the inflammatory bowel diseases (IBD). These disorders have a significant effect on the quality of life of affected patients and the increasing number of IBD cases worldwide is a growing concern. Because of the overall burden of IBD and its multifactorial etiology, efforts have been made to improve the medical management of these inflammatory conditions. The classical therapeutic strategies aim to control the exacerbated host immune response with aminosalicylates, antibiotics, corticosteroids, thiopurines, methotrexate and anti-tumor necrosis factor (TNF) biological agents. Although successful in the treatment of several CD or UC conditions, these drugs have limited effectiveness, and variable responses may culminate in unpredictable outcomes. The ideal therapy should reduce inflammation without inducing immunosuppression, and remains a challenge to health care personnel. Recently, a number of additional approaches to IBD therapy, such as new target molecules for biological agents and cellular therapy, have shown promising results. A deeper understanding of IBD pathogenesis and the availability of novel therapies are needed to improve therapeutic success. This review describes the overall key features of therapies currently employed in clinical practice as well as novel and future alternative IBD treatment methods.

An alternative to the use of animals to teach diabetes mellitus

We developed an alternative approach to teach diabetes mellitus in our practical classes, replacing laboratory animals. We used custom rats made of cloth, which have a ventral zipper that allows stuffing with glass marbles to reach different weights. Three mock rats per group were placed into metabolic cages with real food and water and with test tubes containing artificial urine, simulating a sample collection of 24 h. For each cage, we also provided other test tubes with artificial blood and urine, simulating different levels of hyperglycemia. The artificial "diabetic" urine contained different amounts of anhydrous glucose and acetone to simulate two different levels of glycosuria and ketonuria. The simulated urine of a nondiabetic rat was prepared without the addition of glucose or acetone. An Accu-Chek system is used to analyze glycemia, and glycosuria and ketonuria intensity were analyzed by means of a Urocolor bioassay. In the laboratory classroom, students were told that they would receive three rats to find out which one has type 1 or type 2 diabetes mellitus. To do so, they had to weigh the animals, quantify the water and food ingestion, and analyze the artificial blood and urine for glycemia, glycosuria, and ketonuria. Only at the end of class did we reveal that the urine and blood were artificial. Students were instructed to plot the data in a table, discuss the results within their group, and write an individual report. We have already used this practical class with 300 students, without a single student refusing to participate.

Association among genetic predisposition, gut microbiota, and host immune response in the etiopathogenesis of inflammatory bowel disease

Inflammatory bowel disease (IBD), which includes Crohn's disease (CD) and ulcerative colitis (UC), is a chronic disorder that affects thousands of people around the world. These diseases are characterized by exacerbated uncontrolled intestinal inflammation that leads to poor quality of life in affected patients. Although the exact cause of IBD still remains unknown, compelling evidence suggests that the interplay among immune deregulation, environmental factors, and genetic polymorphisms contributes to the multifactorial nature of the disease. Therefore, in this review we present classical and novel findings regarding IBD etiopathogenesis. Considering the genetic causes of the diseases, alterations in about 100 genes or allelic variants, most of them in components of the immune system, have been related to IBD susceptibility. Dysbiosis of the intestinal microbiota also plays a role in the initiation or perpetuation of gut inflammation, which develops under altered or impaired immune responses. In this context, unbalanced innate and especially adaptive immunity has been considered one of the major contributing factors to IBD development, with the involvement of the Th1, Th2, and Th17 effector population in addition to impaired regulatory responses in CD or UC. Finally, an understanding of the interplay among pathogenic triggers of IBD will improve knowledge about the immunological mechanisms of gut inflammation, thus providing novel tools for IBD control.

Role of central NO-cGMP pathway in vasopressin and oxytocin gene expression during sepsis

Sepsis induces massive production of inflammatory mediators, such as nitric oxide (NO), and causes neuroendocrine and cardiovascular alterations. This study investigates the involvement of the central NO-cGMP pathway in arginine vasopressin (AVP) and oxytocin (OXY) gene expression during sepsis induced by cecal ligation and puncture (CLP). Male Wistar rats received an i.c.v. injection of ODQ (0.25 μg/μL), a selective inhibitor of the heme site of soluble guanylate cyclase, or of 1% dymethilsulfoxide (DMSO), as vehicle. Thirty minutes after the injections, sepsis was induced by cecal ligation and puncture or the animals were sham operated. The ODQ pre-treatment did not alter the progressive NO increase observed after CLP. In the supraoptic nucleus (SON), this pretreatment increased the relative gene expression ratio of AVP and OXY in the initial phase of sepsis, but in the late phase, the gene expression of both hormones was reduced. In the paraventricular nucleus (PVN), soluble guanylate cyclase inhibition caused an even larger decrease in the relative gene expression ratio of AVP and OXY during sepsis. These results are indicative of a role of the NO-cGMP pathway in hormonal synthesis in the SON and PVN of the hypothalamus during polymicrobial sepsis.