Glucose regulation of beta-defensin-1 mRNA in human renal cells

Relationship between biofilm-forming microorganisms (BFM: Staphylococcus aureus and Pseudomonas aeruginosa) and DEFB1 gene variants on β-defensin levels in periprosthetic joint infection (PJI)

BACKGROUND

The purpose of this study was to investigate the relationship between biofilm-forming microorganisms (BFM) and DEFB1 gene variants on β-defensin levels in patients with periprosthetic joint infection (PJI) of Mexican origin.

METHODS AND RESULTS

One hundred and five clinical aspirates were obtained from patients with suspected PJI. After microbiologic culture, samples were classified as non-septic and septic; of the latter, only those positive for Staphylococcus aureus and Pseudomonas aeruginosa were selected. β-Defensin levels were quantified by ELISA, DNA was extracted from total leukocytes of the samples, and - 20G > A (rs11362) and - 44 C > G (rs1800972) variants were genotyped using TaqMan probes. Forty-one clinical aspirates were non-septic, 18 were positive for S. aureus and 18 were positive for P. aeruginosa. It was observed that β-defensin levels were higher in the P. aeruginosa group compared to S. aureus group (2339.0 pg/mL IQR = 1809.2 vs. 1821.3 pg/mL IQR = 1536.4) and non-septic group (2339.0 pg/mL IQR = 1809.2 vs. 1099.7 pg/mL IQR = 1744.5, P < 0.001). The CG genotype of the rs1800972 variant was associated with higher β-defensin levels compared to the CC genotype for both P. aeruginosa and S. aureus (1905.8 vs. 421.7 pg/mL, P = 0.004; and 1878.2 vs. 256.4 pg/mL, P = 0.006, respectively).

CONCLUSIONS

Our results show that β-defensin levels are significantly elevated in patients with BFM-associated PJI compared to those without infection. Furthermore, carriers of the CG genotype of the rs1800972 variant have an increased risk of PJI. Further research is needed to replicate these findings in a larger population.

Induction of Endogenous Antimicrobial Peptides to Prevent or Treat Oral Infection and Inflammation

Antibiotics are often used to treat oral infections. Unfortunately, excessive antibiotic use can adversely alter oral microbiomes and promote the development of antibiotic-resistant microorganisms, which can be difficult to treat. An alternate approach could be to induce the local transcription and expression of endogenous oral antimicrobial peptides (AMPs). To assess the feasibility and benefits of this approach, we conducted literature searches to identify (i) the AMPs expressed in the oral cavity; (ii) the methods used to induce endogenous AMP expression; and (iii) the roles that expressed AMPs may have in regulating oral inflammation, immunity, healing, and pain. Search results identified human neutrophil peptides (HNP), human beta defensins (HBD), and cathelicidin AMP (CAMP) gene product LL-37 as prominent AMPs expressed by oral cells and tissues. HNP, HBD, and LL-37 expression can be induced by micronutrients (trace elements, elements, and vitamins), nutrients, macronutrients (mono-, di-, and polysaccharides, amino acids, pyropeptides, proteins, and fatty acids), proinflammatory agonists, thyroid hormones, and exposure to ultraviolet (UV) irradiation, red light, or near infrared radiation (NIR). Localized AMP expression can help reduce infection, inflammation, and pain and help oral tissues heal. The use of a specific inducer depends upon the overall objective. Inducing the expression of AMPs through beneficial foods would be suitable for long-term health protection. Additionally, the specialized metabolites or concentrated extracts that are utilized as dosage forms would maintain the oral and intestinal microbiome composition and control oral and intestinal infections. Inducing AMP expression using irradiation methodologies would be applicable to a specific oral treatment area in addition to controlling local infections while regulating inflammatory and healing processes.

Altered Expression of Antimicrobial Peptides in the Upper Gastrointestinal Tract of Patients with Diabetes Mellitus

Antimicrobial peptides (AMP) are essential components of innate immunity with a broad range of antimicrobial activities against bacteria, viruses, and fungi. The aim of this study was to investigate AMP expression in the upper gastrointestinal tract in normal and pathological metabolic states in humans. Furthermore, we examined the correlation between vitamin D levels and AMP expression in the same cohort. Serum concentrations of 25-hydroxyvitamin D3 were measured, and mRNA expression of β-defensins HBD-1, -2, -3, -4, α-defensins HD-5 and -6 and cathelicidin in the upper gastrointestinal tract epithelia were determined by quantitative RT-PCR in 31 individuals (10 with type 2 diabetes, 10 with insulin resistance, and 11 healthy controls). The majority of the cohort showed low vitamin D concentrations, which were negatively correlated with mRNA expression levels of HBD-3 in corpus mucosa. HBD-1 and HBD-3 mRNA were expressed in corpus mucosa, with the former significantly decreased in patients with diabetes. Hence, we conclude that type 2 diabetes is associated with reduced AMP expression in the upper gastrointestinal tract, which might contribute towards epithelial barrier dysfunction and increased bacterial translocation in these patients.

Preventing Respiratory Viral Diseases with Antimicrobial Peptide Master Regulators in the Lung Airway Habitat

The vast surface area of the respiratory system acts as an initial site of contact for microbes and foreign particles. The whole respiratory epithelium is covered with a thin layer of the airway and alveolar secretions. Respiratory secretions contain host defense peptides (HDPs), such as defensins and cathelicidins, which are the best-studied antimicrobial components expressed in the respiratory tract. HDPs have an important role in the human body's initial line of defense against pathogenic microbes. Epithelial and immunological cells produce HDPs in the surface fluids of the lungs, which act as endogenous antibiotics in the respiratory tract. The production and action of these antimicrobial peptides (AMPs) are critical in the host's defense against respiratory infections. In this study, we have described all the HDPs secreted in the respiratory tract as well as how their expression is regulated during respiratory disorders. We focused on the transcriptional expression and regulation mechanisms of respiratory tract HDPs. Understanding how HDPs are controlled throughout infections might provide an alternative to relying on the host's innate immunity to combat respiratory viral infections.

Synergistic Induction of Chicken Antimicrobial Host Defense Peptide Gene Expression by Butyrate and Sugars

Antimicrobial resistance is a major concern to public health demanding effective alternative strategies to disease control and prevention. Modulation of endogenous host defense peptide (HDP) synthesis has emerged as a promising antibiotic alternative approach. This study investigated a potential synergy between sugars and butyrate in inducing HDP gene expression in chickens. Our results revealed that sugars differentially regulated HDP expression in both gene- and sugar-specific manners in chicken HD11 macrophage cells. Among eight mono- and disaccharides tested, all were potent inducers of avian β-defensin 9 (AvBD9) gene (p<0.05), but only galactose, trehalose, and lactose obviously upregulated cathelicidin-B1 (CATHB1) gene expression. The expression of AvBD14 gene, on the other hand, was minimally influenced by sugars. Moreover, all sugars exhibited a strong synergy with butyrate in enhancing AvBD9 expression, while only galactose, trehalose, and lactose were synergistic with butyrate in CATHB1 induction. No synergy in AvBD14 induction was observed between sugars and butyrate. Although lactose augmented the expression of nearly all HDP genes, its synergy with butyrate was only seen with several, but not all, HDP genes. Mucin-2 gene was also synergistically induced by a combination of lactose and butyrate. Furthermore, lactose synergized with butyrate to induce AvBD9 expression in chicken jejunal explants (p<0.05). Mechanistically, hyper-acetylation of histones was observed in response to both butyrate and lactose, relative to individual compounds. Mitogen-activated protein kinase, NF-κB, and cyclic adenosine monophosphate signaling pathways were also found to be involved in butyrate- and lactose-mediated synergy in AvBD9 induction. Collectively, a combination of butyrate and a sugar with both HDP-inducing and barrier protective activities holds the promise to be developed as an alternative to antibiotics for disease control and prevention.

Host Defence Peptides in Diabetes Mellitus Type 2 Patients with Periodontal Disease. A Systematic Review

The aim of the study was to critically assess and review the latest evidence relating the associations between host defence peptides (HDPs), periodontal diseases (PD) and diabetes mellitus type 2 (DM2). To explore studies on HDPs, periodontal disease, and DM2, researchers utilised specific key phrases to search the electronic databases PubMed (National Library of Medicine), Embase (Ovid), Medline (EBSCO), and Dentistry and Oral Sciences (EBSCO). Quality assessment was conducted by means of the Newcastle Ottawa scale and the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) tool. Following a thorough screening process, a total of 12 papers (4 case-control, 6 cross-sectional, 1 animal, and 1 in vitro) fulfilled the selection criteria and were included. The majority of research found that HDPs were upregulated in DM2 patients with PD. Three investigations, however, found that HDPs were downregulated in DM2 patients with PD. HDPs play a part in the pathophysiology of PD and DM2. Nonetheless, more human, animal and laboratory investigations are needed to fully understand validation of the link, as the evidence is limited. Understanding HDPs as common moderators is critical, aimed at unlocking their potential as therapeutic and diagnostic agents.

Luminal microvesicles uniquely influence translocating bacteria after SIV infection

Microbial translocation contributes to persistent inflammation in both treated and untreated HIV infection. Although translocation is due in part to a disintegration of the intestinal epithelial barrier, there is a bias towards the translocation of Proteobacteria. We hypothesized that intestinal epithelial microvesicle cargo differs after HIV infection and contributes to biased translocation. We isolated gastrointestinal luminal microvesicles before and after progressive simian immunodeficiency virus (SIV) infection in rhesus macaques and measured miRNA and antimicrobial peptide content. We demonstrate that these microvesicles display decreased miR-28-5p, -484, -584-3p, and -584-5p, and let-7b-3p, as well as increased beta-defensin 1 after SIV infection. We further observed dose-dependent growth sensitivity of commensal Lactobacillus salivarius upon co-culture with isolated microvesicles. Infection-associated microvesicle differences were not mirrored in non-progressively SIV-infected sooty mangabeys. Our findings describe novel alterations of antimicrobial control after progressive SIV infection that influence the growth of translocating bacterial taxa. These studies may lead to the development of novel therapeutics for treating chronic HIV infection, microbial translocation, and inflammation.

Inducible expression of defensins and cathelicidins by nutrients and associated regulatory mechanisms

Host defense peptides (HDPs) are crucial components of the body's first line of defense that protect organisms from infections and mediate immune responses. Defensins and cathelicidins are the two most important families of HDPs in mammals. In this review, we summarize the nutrients that are involved in inducible expression of endogenous defensins and cathelicidins. In addition, the mitogen-activated protein kinases (MAPK), nuclear factor kappa B (NF-κB) and histone deacetylase (HDAC) signaling pathways that play vital roles in the induction of defensin and cathelicidin expression are highlighted. Endogenous defensins and cathelicidins induced by nutrients may be potential alternatives to antibiotic treatments against infection and diseases. This review mainly focuses on the inducible expression and regulatory mechanisms of defensins and cathelicidins in multiple species by different nutrients and the potential applications of defensin- and cathelicidin-inducing nutrients.

The -44 C/G (rs1800972) polymorphism of the β-defensin 1 is associated with increased risk of developing type 2 diabetes mellitus

Background

The aim of this study was to establish the association of two polymorphisms of the β‐defensin 1 gene (DEFB1, OMIM#602056) with the risk of developing type 2 diabetes mellitus (T2DM) in a group of Mexican patients.

Methods

The 5′UTR −20 G/A, and −44 C/G polymorphisms of DEFB1 gene were genotyped by 5′ exonuclease TaqMan assays in a group of 252 patients with T2DM and 522 healthy control.

Results

Under dominant and additive models adjusted for the risk factors, the C allele of the −44 C/G polymorphism was associated with increased risk of T2DM (OR = 1.63, 95% CI = 1.07–2.48, pC_dom = 0.021 and OR = 1.42, 95% CI = 1.05–1.91, pC_add = 0.023, respectively). In addition, the linkage disequilibrium analysis showed that AC haplotype was associated with an increased risk of developing T2DM (OR = 4.39, p = 0.04). The in‐silico analysis showed that the −44 C allele produces a binding site for the transcription factor Ikaros (IK).

Conclusion

This study demonstrates that the C allele of −44 C/G polymorphism, as well as haplotype AC are associated with the presence of T2DM in the Mexican population. The variation in this polymorphism of the DEFB1 gene could increase the migration of the macrophages to pancreatic islets accelerate the β‐cell dysfunction in T2DM.

Insulin and the phosphatidylinositol 3-kinase signaling pathway regulate Ribonuclease 7 expression in the human urinary tract

Diabetes mellitus is a systemic disease associated with a deficiency of insulin production or action. Diabetic patients have an increased susceptibility to infection with the urinary tract being the most common site. Recent studies suggest that Ribonuclease 7 (RNase 7) is a potent antimicrobial peptide that plays an important role in protecting the urinary tract from bacterial insult. Because the impact of diabetes on RNase 7 expression and function are unknown, we investigated the effects of insulin on RNase 7 using human urine specimens. The urinary RNase 7 concentrations were measured in healthy control patients and insulin-deficient type 1 diabetics before and after starting insulin therapy. Compared with controls, diabetic patients had suppressed urinary RNase 7 concentrations, which increased with insulin. Using primary human urothelial cells, the mechanisms by which insulin stimulates RNase 7 synthesis were next explored. Insulin induced RNase 7 production via the phosphatidylinositide 3-kinase signaling pathway (PI3K/AKT) to shield urothelial cells from uropathogenic E. coli. In contrast, uropathogenic E. coli suppressed PI3K/AKT activity and RNase 7 production. Thus, insulin and PI3K/AKT signaling are essential for RNase 7 expression and increased infection risks in diabetic patients may be secondary to suppressed RNase 7 production. Our data may provide unique insight into novel urinary tract infection therapeutic strategies in at-risk populations.

Increased expression of mitochondrial DNA-encoded genes in human renal mesangial cells in response to high glucose-induced reactive oxygen species

Reactive oxygen species (ROS)-mediated disruption of mitochondrial respiratory function has been implicated in the complications of diabetes. The present study examined changes in the gene expression of mitochondrial DNA (mtDNA)-encoded subunits of electron transport chain complexes in response to high glucose-induced ROS overproduction in an in vitro model of diabetic nephropathy using human renal mesangial cells. Mitochondrial ROS generation was assessed by confocal microscopy and flow cytometry in the cells following culture in 5 and 25 mM glucose. The mRNA expression levels of nicotinamide adenine dinucleotide dehydrogenase 2 (ND2) of complex I, cytochrome b (CYTB) of complex III, cytochrome c oxidase (COI) of complex IV and ATPase 6 of complex V were analyzed by reverse transcription-quantitative polymerase chain reaction. The protein expression levels of ND2, CYTB, COI and ATPase 6 were analyzed by western blotting. A significant increase in mitochondrial ROS production was observed in the cells cultured in 25 mM glucose, compared with cells cultured in 5 mM glucose (P<0.05). The mRNA expression of ND2, CYTB, CO1 and ATPase 6 was significantly increased following culture in 25 mM glucose, compared with the cells cultured in 5 mM glucose (P<0.05). This increase in mRNA expression was accompanied by significant increases in protein expression following incubation in 25 mM glucose (P<0.05). The increase in mtDNA-encoded gene expression in the electron transport subunits following exposure to high glucose-induced ROS may be a compensatory response mechanism for the decline in mitochondrial function, which may be important in the development of diabetic nephropathy through enhanced ROS generation.

Time-course effect of high-glucose-induced reactive oxygen species on mitochondrial biogenesis and function in human renal mesangial cells

The present study investigated the time-course effect of high-glucose-induced reactive oxygen species (ROS) on mitochondrial biogenesis and function in human renal mesangial cells and the effect of direct inhibition of ROS on mitochondria. The cells were cultured for 1, 4, and 7 days in normal glucose or high glucose in the presence and absence of Mn(III)tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP) or catalase. Mitochondrial ROS production was assessed by confocal microscope. mtDNA copy number and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), nuclear respiratory factors 1 (NRF-1), and mitochondrial transcription factor A (TFAM) transcripts were analyzed by real-time PCR. PGC-1α, NRF-1, and TFAM proteins were analyzed by Western blotting. Mitochondrial function was determined by assessing mitochondrial membrane potential and adenosine triphosphate (ATP) levels. High glucose induced significant increases in mitochondrial superoxide and hydrogen peroxide (H2 O2 ) at day 1, which remained significantly elevated at days 4 and 7. The copy number of mtDNA and expression of PGC-1α, NRF-1, and TFAM were significantly increased at 1 day in high glucose but were significantly decreased at 4 and 7 days. A progressive decrease in mitochondrial membrane potential was observed at 1, 4, and 7 days in high glucose, and this was associated with decreased ATP levels. Treatment of cells with MnTBAP or catalase during high-glucose incubation attenuated ROS production and reversed the alterations in mitochondrial biogenesis and function. Increased mitochondrial biogenesis in human renal mesangial cells may be an early adaptive response to high-glucose-induced ROS, and prolonged ROS production induced by chronic high glucose decreased mitochondrial biogenesis and impaired mitochondrial function. Protection of mitochondria from high-glucose-induced ROS may provide a potential approach to retard the development and progression of diabetic nephropathy.

Overexpressions of hBD-2, hBD-3, and hCAP18/LL-37 in Gingiva of Diabetics with Periodontitis

Antimicrobial peptides of the epithelium play a significant role in the innate immune response in the oral cavity, which is constantly exposed to microbes. Type 2 diabetes mellitus (T2DM) is a highly prevalent metabolic disease which is related to periodontal disease. To date, little is known about expressions of antimicrobial peptides in gingival epithelia of diabetics. Our aim was to examine the expression and localization of human beta-defensins (hBD)-2 and -3 and cathelicidin (hCAP18/LL-37) in diabetic subjects suffering from generalized periodontitis (GP). Gingival tissue sections were collected from three subject groups: 14 T2DM subjects with GP (T2DM+GP), 11 systemically healthy GP patients (GP), and 13 systemically and periodontally healthy subjects (control). Surgical incisions targeted the sulcular epithelium and/or the bottom of the selected periodontal pocket. Tissue specimens were fixed in paraformaldehyde and embedded in paraffin blocks. Immunohistochemistry stainings were performed for cytokeratin19, hBD-2, hBD-3 and hCAP18/LL-37. Stainings were examined under light microscope with 40× magnification. Results were statistically evaluated by the t-test. In controls, hBD-2 was localized at the superficial layers of the gingival epithelium, hBD-3 and hCAP18/LL-37 were at the basal layers, whereas in subjects with periodontitis both defensins were visible at all epithelial layers. hBD-2 was detected in the nucleus and cytoplasm, while hBD-3 and hCAP18/LL-37 were detected only in the cytoplasm of the cells. Expressions of hBD-2 (p=0.005), hBD-3 (p=0.007), and hCAP18/LL-37 (p=0.002) were elevated in subjects with T2DM+GP in comparison to controls. No statistically significant difference was found in the expression of hBD-2, -3, and hCAP18/LL-37 between the GP group and the control or T2DM+GP groups. Gingival antimicrobial peptides are overexpressed in T2DM. This outcome can be part of impaired immune response in diabetics, and underlying factors and mechanisms need to be elucidated.

Ascorbic acid, ultraviolet C rays, and glucose but not hyperthermia are elicitors of human β-defensin 1 mRNA in normal keratinocytes

Hosts' innate defense systems are upregulated by antimicrobial peptide elicitors (APEs). Our aim was to investigate the effects of hyperthermia, ultraviolet A rays (UVA), and ultraviolet C rays (UVC) as well as glucose and ascorbic acid (AA) on the regulation of human β-defensin 1 (DEFB1), cathelicidin (CAMP), and interferon-γ (IFNG) genes in normal human keratinocytes (NHK). The indirect in vitro antimicrobial activity against Staphylococcus aureus and Listeria monocytogenes of these potential APEs was tested. We found that AA is a more potent APE for DEFB1 than glucose in NHK. Glucose but not AA is an APE for CAMP. Mild hypo- (35°C) and hyperthermia (39°C) are not APEs in NHK. AA-dependent DEFB1 upregulation below 20 mM predicts in vitro antimicrobial activity as well as glucose- and AA-dependent CAMP and IFNG upregulation. UVC upregulates CAMP and DEFB1 genes but UVA only upregulates the DEFB1 gene. UVC is a previously unrecognized APE in human cells. Our results suggest that glucose upregulates CAMP in an IFN-γ-independent manner. AA is an elicitor of innate immunity that will challenge the current concept of late activation of adaptive immunity of this vitamin. These results could be useful in designing new potential drugs and devices to combat skin infections.

Markers of innate immune activity in patients with type 1 and type 2 diabetes mellitus and the effect of the anti-oxidant coenzyme Q10 on inflammatory activity

Major long-term complications in patients with diabetes are related to oxidative stress, caused by the hyperglycaemia characteristic for diabetes mellitus. The anti-oxidant coenzyme Q10 (CoQ10) has therefore been proposed as a beneficial supplement to diabetes treatment. Apart from its anti-oxidative function, CoQ10 appears to modulate immune functions by largely unknown mechanisms. The aim of this study was therefore to investigate the effect of CoQ10 on antimicrobial peptides and natural killer (NK) cells, both innate immune components implicated in the pathogenesis of diabetes and diabetes-associated long-term complications such as cardiovascular disease. We determined serum levels of antimicrobial peptides and the phenotype of NK cells isolated from peripheral blood of patients with type 1 (T1DM) or type 2 diabetes mellitus (T2DM) and from healthy controls. In addition, the same parameters were determined in diabetic patients after a 12-week period of CoQ10 supplementation. Two antimicrobial peptides, the human cathelicidin antimicrobial peptide (CAMP) and the human beta defensin 1 (hBD1), were reduced in serum from patients with T1DM. This defect was not reversible by CoQ10 supplementation. In contrast, CoQ10 reduced the levels of circulating hBD2 in these patients and induced changes in subset distribution and activation markers in peripheral NK cells. The results of the present study open up novel approaches in the prevention of long-term complications associated to T1DM, although further investigations are needed.

Profile of human β-defensins 1,2 and proinflammatory cytokines (TNF-α, IL-6) in patients with chronic kidney disease

BACKGROUND/AIM

Our aim was to determine whether altered human β-defensin (HBD), pro-inflammatory cytokines including interleukin (IL)-6 and tumor necrotic factor (TNF)-α could increase the risk of developing and exacerbation of chronic kidney disease (CKD), especially for patients with diabetic nephropathy (DN).

METHODS

Serum samples were obtained from 338 CKD patients and 88 sex, age-matched healthy controls. The concentrations of HBD-1 were assayed using an RIA kit. Serum levels of HBD-2, IL-6 and TNF-α were assayed using an ELISA kit.

RESULTS

Serum levels of HBD-1, IL-6 and TNF-α were significantly higher in CKD patients compared to healthy controls (P<0.05). HBD-1 levels were inversely related to estimated glomerular filtration rate (eGFR), which was the coefficient factor (β = -0.357, P = 0.035) explaining the variability in HBD-1 in CKD. Diabetic nephropathy (DN) patients at stage 3-5 had significantly higher serum HBD-1 levels than non DN patients (P=0.00).

CONCLUSION

Our data support the view that there is increased inflammation in CKD and DN. The inverse correlation between eGFR and serum HBD-1 which we observed is suggestive of a relationship between innate immunity and renal function and should be further investigated.

Fundamental role for HIF-1α in constitutive expression of human β defensin-1

Antimicrobial peptides are secreted by the intestinal epithelium to defend from microbial threats. The role of human β defensin-1 (hBD-1) is notable because its gene (beta-defensin 1 (DEFB1)) is constitutively expressed and its antimicrobial activity is potentiated in the low-oxygen environment that characterizes the intestinal mucosa. Hypoxia-inducible factor (HIF) is stabilized even in healthy intestinal mucosa, and we identified that epithelial HIF-1α maintains expression of murine defensins. Extension to a human model revealed that basal HIF-1α is critical for the constitutive expression of hBD-1. Chromatin immunoprecipitation identified HIF-1α binding to a hypoxia response element in the DEFB1 promoter whose importance was confirmed by site-directed mutagenesis. We used 94 human intestinal samples to identify a strong expression correlation between DEFB1 and the canonical HIF-1α target GLUT1. These findings indicate that basal HIF-1α is critical for constitutive expression of enteric DEFB1 and support targeting epithelial HIF for restoration and maintenance of intestinal integrity.

Antimicrobial peptides and gut microbiota in homeostasis and pathology

We survive because we adapted to a world of microorganisms. All our epithelial surfaces participate in keeping up an effective barrier against microbes while not initiating ongoing inflammatory processes and risking collateral damage to the host. Major players in this scenario are antimicrobial peptides (AMPs). Such broad-spectrum innate antibiotics are in part produced by specialized cells but also widely sourced from all epithelia as well as circulating inflammatory cells. AMPs belong to an ancient defense system found in all organisms and participated in a preservative co-evolution with a complex microbiome. Particularly interesting interactions between host barrier and microbiota can be found in the gut. The intestinal cell lining not only has to maintain a tightly regulated homeostasis during its high-throughput regeneration, but also a balanced relationship towards an extreme number of mutualistic or commensal inhabitants. Recent research suggests that advancing our understanding of the circumstances of such balanced and sometimes imbalanced interactions between gut microbiota and host AMPs should have therapeutic implications for different intestinal disorders.

High glucose-induced oxidative stress increases the copy number of mitochondrial DNA in human mesangial cells

Oxidative damage to mitochondrial DNA (mtDNA) has been linked to the pathogenicity of diabetic nephropathy. We tested the hypothesis that mtDNA copy number may be increased in human mesangial cells in response to high glucose-induced reactive oxygen species (ROS) to compensate for damaged mtDNA. The effect of manganese superoxide dismutase mimetic (MnTBAP) on glucose-induced mtDNA copy number was also examined. The copy number of mtDNA was determined by real-time PCR in human mesangial cells cultured in 5 mM glucose, 25 mM glucose, and mannitol (osmotic control), as well as in cells cultured in 25 mM glucose in the presence and absence of 200 μM MnTBAP. Intracellular ROS was assessed by confocal microscopy and flow cytometry in human mesangial cells. The copy number of mtDNA was significantly increased when human mesangial cells were incubated with 25 mM glucose compared to 5 mM glucose and mannitol. In addition, 25 mM glucose rapidly generated ROS in the cells, which was not detected in 5 mM glucose. Furthermore, mtDNA copy number was significantly decreased and maintained to normal following treatment of cells with 25 mM glucose and MnTBAP compared to 25 mM glucose alone. Inclusion of MnTBAP during 25 mM glucose incubation inhibited mitochondrial superoxide in human mesangial cells. Increased mtDNA copy number in human mesangial cells by high glucose could contribute to increased mitochondrial superoxide, and prevention of mtDNA copy number could have potential in retarding the development of diabetic nephropathy.

Nop-7-associated 2 (NSA2), a candidate gene for diabetic nephropathy, is involved in the TGFβ1 pathway

We recently showed that Nop-7-associated 2 (NSA2) originally described in yeast as a nuclear protein involved in ribosomal biogenesis, is a hyperglycemia induced gene involved in diabetic nephropathy [Shahni et al., Elevated levels of renal and circulating Nop-7-associated 2 (NSA2) in rat and mouse models of diabetes, in mesangial cells in vitro and in patients with diabetic nephropathy. Diabetologia 2012;55(March(3)):825-34]. However the function of NSA2 in the cell remains unknown. In the current paper we investigate the possible mechanisms for the involvement of NSA2 in diabetic nephropathy by testing the hypothesis that NSA2 expression is linked to the TGFβ1 pathway. Both TGFβ1 and NSA2 mRNAs were significantly up-regulated in cultured renal mesangial cells in response to high glucose, in mouse kidneys during hyperglycemia, and in developing kidneys of mouse embryos during mesenchymal to epithelial transition. Surprisingly, the previously described nuclear NSA2 protein was predominantly located in the cytosol of cultured renal cells. Exogenous TGFβ1 could elevate NSA2 mRNA/protein levels in cultured mesangial cells and could also affect the cellular localization of NSA2, causing the predominantly cytosolic NSA2 protein to rapidly translocate to the nucleus. Increased NSA2 nuclear staining was seen in diabetic mouse kidneys compared to control kidneys. Knock-down of NSA2 expression using RNA interference resulted in significantly decreased TGFβ1 mRNA/protein, almost abolished TGFβ1 activity, and resulted in significantly reduced mRNA levels of the TGFβ1 downstream gene fibronectin. Our data suggest that NSA2 is acting upstream of the TGFβ1 pathway and that NSA2 is needed for TGFβ1 expression and transcriptional activity. In summary, NSA2, which increases in diabetic nephropathy, may be involved in the actions of TGFβ1 and contribute to the development of diabetic nephropathy.

Do β-defensins and other antimicrobial peptides play a role in neuroimmune function and neurodegeneration?

It is widely accepted that the brain responds to mechanical trauma and development of most neurodegenerative diseases with an inflammatory sequelae that was once thought exclusive to systemic immunity. Mostly cationic peptides, such as the β-defensins, originally assigned an antimicrobial function are now recognized as mediators of both innate and adaptive immunity. Herein supporting evidence is presented for the hypothesis that neuropathological changes associated with chronic disease conditions of the CNS involve abnormal expression and regulatory function of specific antimicrobial peptides. It is also proposed that these alterations exacerbate proinflammatory conditions within the brain that ultimately potentiate the neurodegenerative process.

Elevated levels of renal and circulating Nop-7-associated 2 (NSA2) in rat and mouse models of diabetes, in mesangial cells in vitro and in patients with diabetic nephropathy

AIMS/HYPOTHESIS

We previously found that Nop-7-associated 2 (NSA2), which is involved in ribosomal biogenesis in yeast and is a putative cell cycle regulator in mammalian cells, is elevated in the kidney of Goto-Kakizaki (GK) rat, a spontaneous model of type 2 diabetes. Here we tested the hypothesis that elevated NSA2 is involved in diabetic nephropathy (DN).

METHODS

We examined Nsa2/NSA2 expression and NSA2 production in two rodent models of diabetes, in cultured renal glomerular cells, and in diabetic patients with and without nephropathy. Patients with nephropathy who had a history of albuminuria were further divided as responders (DN-NA; DN patients normoalbuminuric at the time of this study with a history of albuminuria) and non-responders (DN-A; diabetic nephropathy patients with albuminuria) to current treatment for albuminuria.

RESULTS

Renal Nsa2/NSA2 mRNA increased in tandem with hyperglycaemia in GK rats, in a streptozotocin-induced mouse model of diabetes, and in human mesangial cells (HMCs) grown in high glucose (p < 0.05). In the mouse model of diabetes, hyperglycaemia resulted in increased Nsa2 expression and NSA2 levels in tubular and glomerular cells and in circulating cells; this increase was normalised by diabetes treatment. Circulating NSA2 mRNA levels were elevated in patients with DN independently of body weight (BMI), glycaemic (HbA(1c)) and haemodynamic (blood pressure) control, and showed an inverse correlation with renal function (GFR, p < 0.05). NSA2 levels were the only variable that showed a significant difference between patients with albuminuria (DN-A) compared with non-albuminuric patients (DN-NA) and diabetic controls (p < 0.05), this increase being independent of all other variables, including GFR.

CONCLUSION

We show for the first time that renal and circulating NSA2/NSA2 levels are increased in hyperglycaemia in experimental models of diabetes, and that circulating NSA2 is elevated in DN patients with albuminuria. Further studies will be required to assess whether NSA2 plays a role in the pathogenesis of DN.

Hyperglycemia induces elevated expression of thyroid hormone binding protein in vivo in kidney and heart and in vitro in mesangial cells

During a search for glucose-regulated abundant mRNAs in the diabetic rat kidney, we cloned thyroid hormone binding protein (THBP), also known as mu-crystallin or CRYM. The aim of this study was to investigate the effect of hyperglycemia/high glucose on the expression of THBP. THBP mRNA copy numbers were determined in kidneys and hearts of diabetic GK rats vs normoglycemic Wistar rats, and in human mesangial cells (HMCs) exposed to high glucose using real-time qPCR, and THBP protein levels were measured by Western blotting and immunofluorescence. Intracellular ROS was measured in THBP transfected cells using DCF fluorescence. Hyperglycemia significantly increased THBP mRNA in GK rat kidneys (326+/-50 vs 147+/-54, p<0.05), and hearts (1583+/-277 vs 191+/-63, p<0.05). Moreover, the levels of THBP mRNA increased with age and hyperglycemia in GK rat kidneys, whereas in normoglycemic Wistar rat kidneys there was a decline with age. High glucose significantly increased THBP mRNA (92+/-37 vs 18+/-4, p<0.005), and protein in HMCs. The expression of THBP as a fusion protein in transfected HMCs resulted in reduction of glucose-induced intracellular ROS. We have shown that THBP mRNA is increased in diabetic kidney and heart, is regulated by high glucose in renal cells, and appears to attenuate glucose-induced intracellular ROS. These data suggest that THBP may be involved in the cellular pathways activated in response to glucose. This is the first report linking hyperglycemia with THBP and suggests that the role of THBP in diabetic complications should be further investigated.

Functional polymorphisms of DEFB1 gene in type 1 diabetes Brazilian children

We analyzed three functional 5' un-translated region beta-defensin 1 (DEFB1) single nucleotide polymorphism (SNPs) in a group of 170 type 1 diabetes (T1D) patients. In order to evaluate the SNPs influence on the disease onset and the development of other autoimmune disorder, such as celiac disease (CD) and autoimmune thyroid disease (AITD), patients were stratified according to the presence of AITD, CD, and both AITD and CD. As control group, we studied 191 healthy children and adolescent not presenting a familiar historic of T1D, CD or AITD. DEFB1 SNPs were in Hardy-Weinberg equilibrium both in healthy controls and T1D patients, as well in the T1D patients stratified according to the presence of other autoimmune disorder(s). Allele, genotype, and haplotype frequencies of T1D patients globally considered were comparable to healthy controls ones. No evidence of any association of DEFB1 SNPs with the onset of AIDT, CD, and both AITD and CD on T1D patients was evidenced. Only a minor trend was found for an increased frequency of the - 20 G allele in T1D patients only presenting AITD vs. T1D patients not presenting AITD or CD, as well as an increase of those haplotypes comprising the - 20 G allele when compared with the GCA haplotype. We also evaluated the influence of functional DEFB1 SNPs on the age of T1D onset: no significant statistical conclusion was achieved. Further studies are envisaged, in order to elucidate the possible role of functional DEFB1 polymorphisms in the onset of TD1 and other autoimmune-related disorders.

Glucose and insulin are needed for optimal defensin expression in human cell lines

Many infections are associated with diabetes, as the ability of the body to fight pathogens is impaired. Recently, low levels of defensins have been found in diabetic rodents. However, whether hyperglycemia and/or insulin deficiency/insensitivity is the reason for the reduced defensin levels is still unknown. To study the functionality of the innate immune system during hyperglycemia, the expression levels of human beta-defensin-1 (hBD-1) was measured in human embryonic kidney (HEK-293) and colon adenocarcinoma (HCT-116) cells treated with different concentrations of glucose and insulin. Increasing concentrations of glucose enhanced hBD-1 expression and these levels were further elevated after insulin treatment. Insulin treatment also led to the up-regulation of human sodium/glucose transporter 1 (hSGLT1), which further increases intracellular glucose levels. Thus, our findings suggest for the first time that insulin signaling is important for hBD-1 optimal expression by elevating intracellular glucose levels and by mediating gene expression.

Defensins in the immunology of bacterial infections

Defensins are a component of the host response against bacterial infections. Multiple studies suggest a linked upregulation of beta-defensins and pro-inflammatory cytokines expression in various tissues, as well as the possibility of mutual induction. Recent data demonstrate the importance of nucleotide-binding oligomerization proteins for the expression of defensins, and associate low levels of alpha-defensins expression by intestinal Paneth cells with susceptibility to Crohn's disease of the ileum. A novel anti-toxin activity has been identified for several alpha- and theta-defensins, expanding the repertoire of the antimicrobial functions of defensins. It has been shown that bacterial proteins can inactivate the action of defensins, and that pathogen type III secretion systems (T3SS) manipulate defensins expression via T3SS-mediated inhibition of the NF-kappaB pathway.

Glucose regulation of CDK7, a putative thiol related gene, in experimental diabetic nephropathy

We previously described the identification of the 3'end of an unknown gene CDK7 using differential display which appeared to be up-regulated in diabetic kidneys [R.A. Page, C.A. Morris, J.D. Williams, C.J. von Ruhland, A.N. Malik, Isolation of diabetes-associated kidney genes using differential display, Biochem. Biophys. Res. Commun. 232 (1997) 49-53]. Here we show that CDK7 is a putative thiol related gene which is regulated by glucose in human and rat renal cells. CDK7 mRNA increased by >threefold in cultured human mesangial cells grown in high glucose for 4 days. In the kidneys of the GK rat, a model of type II diabetes, CDK7 showed a steady age-related increase in mRNA, increasing to >sixfold in 40 week GK rats compared to normoglycemic age-matched Wistar rat kidneys, this increase correlates with progressive hyperglycemia. CDK7 mRNA is widely expressed, showing particularly high levels of expression in rat and human liver, and encodes a putative 338 amino acids highly conserved peptide with several conserved domains, including a cys-pro-arg-cys domain conserved in 15 diverse species which is similar to the catalytic centre of thioredoxin, suggesting a role in oxidative stress.