Protective effects of oyster polypeptide on cyclophosphamide-induced immunosuppressed rats.

BACKGROUND: Oyster polypeptide (OP) is a mixture of oligopeptides extracted from oysters through enzyme lysis, separation, and purification. It is associated with immunomodulatory effects, but the underlying mechanisms are not known. This study therefore combined proton nuclear magnetic resonance (1H-NMR) urinary metabolomics and 16S rRNA gene sequencing of the gut microbiome to determine the immunoprotective mechanisms of OP in rats subjected to cyclophosphamide-induced immunosuppression. RESULTS: Oyster polypeptide restored the body weight and the structure of spleen and thymus in rats with cyclophosphamide-induced immunosuppression. It upregulated the levels of white blood cells (WBCs), hemoglobin (HGB), platelets (PLT), red blood cells (RBCs), immunoglobulin G (IgG), immunoglobulin M (IgM), cytokines such as interleukin­6 (IL-6) and tumor necrosis factor-α (TNF-α), and increased the numbers of CD3+ and CD4+ T cells in the immunosuppressed rats. The 1H-NMR metabolomics results showed that OP significantly reversed the levels of ten metabolites in urine, including 2-oxoglutarate, citrate, dimethylamine, taurine, N-phenylacetylglycine, alanine, betaine, creatinine, uracil, and benzoate. The 16S rRNA gene sequencing results showed that OP restored the gut microbiome homeostasis by increasing the abundance of beneficial bacteria and reducing the abundance of pathogenic bacteria. Finally, a combination of metabolomics and microbiomics found that the metabolism of taurine and hypotaurine, and the metabolism of alanine, aspartate, and glutamate were disturbed, but these metabolic pathways were restored by OP. CONCLUSION: This study demonstrated that OP had immunoprotective effects in rats with cyclophosphamide-induced immunosuppression by restoring key metabolic pathways and the gut microbiome homeostasis. Our findings provide a framework for further research into the immunoregulatory mechanisms of OP and its potential use in drugs and nutritional supplements. © 2024 Society of Chemical Industry.

Epidermal growth factor receptor activation is essential for kidney fibrosis development.

Fibrosis is the progressive accumulation of excess extracellular matrix and can cause organ failure. Fibrosis can affect nearly every organ including kidney and there is no specific treatment currently. Although Epidermal Growth Factor Receptor (EGFR) signaling pathway has been implicated in development of kidney fibrosis, underlying mechanisms by which EGFR itself mediates kidney fibrosis have not been elucidated. We find that EGFR expression increases in interstitial myofibroblasts in human and mouse fibrotic kidneys. Selective EGFR deletion in the fibroblast/pericyte population inhibits interstitial fibrosis in response to unilateral ureteral obstruction, ischemia or nephrotoxins. In vivo and in vitro studies and single-nucleus RNA sequencing analysis demonstrate that EGFR activation does not induce myofibroblast transformation but is necessary for the initial pericyte/fibroblast migration and proliferation prior to subsequent myofibroblast transformation by TGF-ß or other profibrotic factors. These findings may also provide insight into development of fibrosis in other organs and in other conditions.

Expansion of Betatorquevirus and/or Gammatorquevirus in Patients with Severe Clinical Outcomes of the Liver Diseases.

Anellovirus (AV) is a ubiquitous virus in the human population. Individuals can be infected with multiple AV genera and species to form a heterogeneous repertoire, termed the anellome. Using advanced methods, we examined the anellomes from 12 paired serum and liver samples, as well as 2701 subjects with different clinical diagnoses. Overall, anellomes are remarkably individualized, with significant among-group differences (Kruskal-Wallis test p = 6.6 × 10-162 for richness and p = 7.48 × 10-162 for Shannon entropy). High dissimilarity scores (beta diversity) were observed between patient groups, except for paired serum and liver samples. At the population level, the relative abundance of combinational AV genus Betatorquevirus (torque teno mini viruses, TTMV), and Gammatorquevirus (torque teno midi viruses, TTMDV) exhibited an exponential distribution with a low bound point at 32%. Defined by this value, the AV TTMV/TTMDV-expanded anellome was significantly enriched among patients with acute liver failure (31.7%) and liver transplantation (40.7%), compared with other patient groups (χ2 test: p = 4.1 × 10-8-3.2 × 10-3). Therefore, anellome heterogeneity may be predictive of clinical outcomes in certain diseases, such as liver disease. The consistency of anellome between paired serum and liver samples indicates that a liquid biopsy approach would be suitable for longitudinal studies to clarify the causality of the AV TTMV/TTMDV-expanded anellome in the outcomes of liver disease.

EGFR-mediated activation of adipose tissue macrophages promotes obesity and insulin resistance.

Obesity and obesity-related health complications are increasing in prevalence. Adipose tissue from obese subjects has low-grade, chronic inflammation, leading to insulin resistance. Adipose tissue macrophages (ATMs) are a source of proinflammatory cytokines that further aggravate adipocyte dysfunction. In response to a high fat diet (HFD), ATM numbers initially increase by proliferation of resident macrophages, but subsequent increases also result from infiltration in response to chemotactic signals from inflamed adipose tissue. To elucidate the underlying mechanisms regulating the increases in ATMs and their proinflammatory phenotype, we investigated the role of activation of ATM epidermal growth factor receptor (EGFR). A high fat diet increased expression of EGFR and its ligand amphiregulin in ATMs. Selective deletion of EGFR in ATMs inhibited both resident ATM proliferation and monocyte infiltration into adipose tissue and decreased obesity and development of insulin resistance. Therefore, ATM EGFR activation plays an important role in adipose tissue dysfunction.

Cyclooxygenase-2 in adipose tissue macrophages limits adipose tissue dysfunction in obese mice.

Obesity-associated complications are causing increasing morbidity and mortality worldwide. Expansion of adipose tissue in obesity leads to a state of low-grade chronic inflammation and dysregulated metabolism, resulting in insulin resistance and metabolic syndrome. Adipose tissue macrophages (ATMs) accumulate in obesity and are a source of proinflammatory cytokines that further aggravate adipocyte dysfunction. Macrophages are rich sources of cyclooxygenase (COX), the rate limiting enzyme for prostaglandin E2 (PGE2) production. When mice were fed a high-fat diet (HFD), ATMs increased expression of COX-2. Selective myeloid cell COX-2 deletion resulted in increased monocyte recruitment and proliferation of ATMs, leading to increased proinflammatory ATMs with decreased phagocytic ability. There were increased weight gain and adiposity, decreased peripheral insulin sensitivity and glucose utilization, increased adipose tissue inflammation and fibrosis, and abnormal adipose tissue angiogenesis. HFD pair-feeding led to similar increases in body weight, but mice with selective myeloid cell COX-2 still exhibited decreased peripheral insulin sensitivity and glucose utilization. Selective myeloid deletion of the macrophage PGE2 receptor subtype, EP4, produced a similar phenotype, and a selective EP4 agonist ameliorated the metabolic abnormalities seen with ATM COX-2 deletion. Therefore, these studies demonstrated that an ATM COX-2/PGE2/EP4 axis plays an important role in inhibiting adipose tissue dysfunction.

Within-host quantitation of anellovirus genome complexity from clinical samples.

Anellovirus (AV) is a ubiquitous and diverse virus in the human population. An individual can be infected with multiple AV genera and species that form a heterogeneous repertoire, called the anellome. Due to its exceptional genetic diversity, efficient evaluation of anellome complexity remains a methodological challenge. In the current study, AV genome was first enriched from patient serum samples through two-phase rolling circle amplification. Following Illumina sequencing, anellome was analyzed with an advanced bioinformatics pipeline, including read extraction at three similarity levels, de novo assembly, species assignment, and determination of relative abundance among AV variants. The method was validated in the mock sample and then applied to 21 hepatitis C virus (HCV) patients with and without hepatocellular carcinoma (HCC). Overall, there was a large variance regarding AV richness, ranging from 2 to 51 AV species. In contrast to HCV patients without HCC, HCC incidence was associated with reduced richness (12.6 ± 14.4 vs. 35.4 ± 13.6, p = 0.001) and Shannon entropy (0.4 ± 0.34 vs. 0.61 ± 0.12, p = 0.095) at the AV species level. Interestingly, AV genus beta and gamma expanded in the anellome in 7 of 10 HCC patients. These observations shed light on the potential association between anellome and HCC incidence in patients with chronic HCV infection. The method presented here represents a valuable tool to investigate the role of anellome in human health and disease.

Macrophage interferon regulatory factor 4 deletion ameliorates aristolochic acid nephropathy via reduced migration and increased apoptosis.

Aristolochic acid (AA) is the causative nephrotoxic alkaloid in AA nephropathy, which results in a tubulointerstitial fibrosis. AA causes direct proximal tubule damage as well as an influx of macrophages, although the role of macrophages in pathogenesis is poorly understood. Here, we demonstrate that AA directly stimulates migration, inflammation, and ROS production in macrophages ex vivo. Cells lacking interferon regulatory factor 4 (IRF4), a known regulator of macrophage migration and phenotype, had a reduced migratory response, though effects on ROS production and inflammation were preserved or increased relative to WT cells. Macrophage-specific IRF4-knockout mice were protected from both acute and chronic kidney effects of AA administration based on functional and histological analysis. Renal macrophages from kidneys of AA-treated macrophage-specific IRF4-knockout mice demonstrated increased apoptosis and ROS production compared with WT controls, indicating that AA directly polarizes macrophages to a promigratory and proinflammatory phenotype. However, knockout mice had reduced renal macrophage abundance following AA administration. While macrophages lacking IRF4 can adopt a proinflammatory phenotype upon AA exposure, their inability to migrate to the kidney and increased rates of apoptosis upon infiltration provide protection from AA in vivo. These results provide evidence of direct AA effects on macrophages in AA nephropathy and add to the growing body of evidence that supports a key role of IRF4 in modulating macrophage function in kidney injury.

Shining light on chiral inorganic nanomaterials for biological issues.

The rapid development of chiral inorganic nanostructures has greatly expanded from intrinsically chiral nanoparticles to more sophisticated assemblies made by organics, metals, semiconductors, and their hybrids. Among them, lots of studies concerning on hybrid complex of chiral molecules with achiral nanoparticles (NPs) and superstructures with chiral configurations were accordingly conducted due to the great advances such as highly enhanced biocompatibility with low cytotoxicity and enhanced penetration and retention capability, programmable surface functionality with engineerable building blocks, and more importantly tunable chirality in a controlled manner, leading to revolutionary designs of new biomaterials for synergistic cancer therapy, control of enantiomeric enzymatic reactions, integration of metabolism and pathology via bio-to nano or structural chirality. Herein, in this review our objective is to emphasize current research state and clinical applications of chiral nanomaterials in biological systems with special attentions to chiral metal- or semiconductor-based nanostructures in terms of the basic synthesis, related circular dichroism effects at optical frequencies, mechanisms of induced optical chirality and their performances in biomedical applications such as phototherapy, bio-imaging, neurodegenerative diseases, gene editing, cellular activity and sensing of biomarkers so as to provide insights into this fascinating field for peer researchers.

Ammonia Gas Sensor Based on Graphene Oxide-Coated Mach-Zehnder Interferometer with Hybrid Fiber Structure.

A graphene oxide-coated in-fiber Mach-Zehnder interferometer (MZI) formed with a multimode fiber-thin core fiber-multimode fiber (MMF-TCF-MMF) is proposed and experimentally demonstrated for ammonia gas (NH3) sensing. The MZI structure is composed of two segments of MMF of length 2 mm, with a flame-tapered TCF between them as the sensing arm. The MMFs act as mode couplers to split and recombine light owing to the core diameter mismatch with the other fibers. A tapered TCF is formed by the flame melting taper method, resulting in evanescent wave leakage. A layer of graphene oxide (GO) is applied to the tapered region of the TCF to achieve gas adsorption. The sensor operates on the principle of changing the effective refractive index of the cladding mode of a fiber through changing the conductivity of the GO coating by adsorbed NH3 molecules, which gives rise to a phase shift and shows as the resonant dip shifts in the transmission spectrum. So the concentration of the ammonia gas can be obtained by measuring the dip shift. A wavelength-shift sensitivity of 4.97 pm/ppm with a linear fit coefficient of 98.9% is achieved for ammonia gas concentrations in the range of 0 to 151 ppm. In addition, we performed a repetitive dynamic response test on the sensor by charging/releasing NH3 at concentration of 200 ppm and a relative humidity test in a relative humidity range of 35% to 70%, which demonstrates the reusability and stability of the sensor.

Podocyte EGFR Inhibits Autophagy Through Upregulation of Rubicon in Type 2 Diabetic Nephropathy.

Renal epidermal growth factor receptor (EGFR) signaling is activated in models of diabetic nephropathy (DN), and inhibition of the EGFR signaling pathway protects against the development of DN. We have now determined that in cultured podocytes, high glucose led to increases in activation of EGFR signaling but decreases in autophagy activity as indicated by decreased beclin-1 and inhibition of LC3B autophagosome formation as well as increased rubicon (an autophagy inhibitor) and SQSTM1 (autophagy substrate). Either genetic (small interfering [si]EGFR) or pharmacologic (AG1478) inhibition of EGFR signaling attenuated the decreased autophagy activity. In addition, rubicon siRNA knockdown prevented high glucose-induced inhibition of autophagy in podocytes. We further examined whether selective EGFR deletion in podocytes affected the progression of DN in type 2 diabetes. Selective podocyte EGFR deletion had no effect on body weight or fasting blood sugars in either db/db mice or nos3 -/-; db/db mice, a model of accelerated type 2 DN. However selective podocyte EGFR deletion led to relative podocyte preservation and marked reduction in albuminuria and glomerulosclerosis, renal proinflammatory cytokine/chemokine expression, and decreased profibrotic and fibrotic components in nos3 -/-; db/db mice. Podocyte EGFR deletion led to decreased podocyte expression of rubicon, in association with increased podocyte autophagy activity. Therefore, activation of EGFR signaling in podocytes contributes to progression of DN at least in part by increasing rubicon expression, leading to subsequent autophagy inhibition and podocyte injury.

The Role of the EGF Receptor in Sex Differences in Kidney Injury.

BACKGROUND: Sex differences mediating predisposition to kidney injury are well known, with evidence indicating lower CKD incidence rates and slower decline in renal function in nondiabetic CKD for premenopausal women compared with men. However, signaling pathways involved have not been elucidated to date. The EGF receptor (EGFR) is widely expressed in the kidney in glomeruli and tubules, and persistent and dysregulated EGFR activation mediates progressive renal injury. METHODS: To investigate the sex differences in response to renal injury, we examined EGFR expression in mice, in human kidney tissue, and in cultured cell lines. RESULTS: In wild type mice, renal mRNA and protein EGFR levels were comparable in males and females at postnatal day 7 but were significantly lower in age-matched adult females than in adult males. Similar gender differences in renal EGFR expression were detected in normal adult human kidneys. In Dsk5 mutant mice with a gain-of-function allele that increases basal EGFR kinase activity, males had progressive glomerulopathy, albuminuria, loss of podocytes, and tubulointerstitial fibrosis, but female Dsk5 mice had minimal kidney injury. Oophorectomy had no effect on renal EGFR levels in female Dsk5 mice, while castration protected against the kidney injury in male Dsk5 mice, in association with a reduction in EGFR expression to levels seen in females. Conversely, testosterone increased EGFR expression and renal injury in female Dsk5 mice. Testosterone directly stimulated EGFR expression in cultured kidney cells. CONCLUSIONS: These studies indicate that differential renal EGFR expression plays a role in the sex differences in susceptibility to progressive kidney injury that may be mediated at least in part by testosterone.

Circular RNA Profiling by Illumina Sequencing via Template-Dependent Multiple Displacement Amplification.

Circular RNAs (circRNAs) are newly discovered incipient non-coding RNAs with potential roles in disease progression in living organisms. Significant reports, since their inception, highlight the abundance and putative functional roles of circRNAs in every organism checked for, like O. sativa, Arabidopsis, human, and mouse. CircRNA expression is generally less than their linear mRNA counterparts which fairly explains the competitive edge of canonical splicing over non-canonical splicing. However, existing methods may not be sensitive enough for the discovery of low-level expressed circRNAs. By combining template-dependent multiple displacement amplification (tdMDA), Illumina sequencing, and bioinformatics tools, we have developed an experimental protocol that is able to detect 1,875 novel and known circRNAs from O. sativa. The same method also revealed 9,242 putative circRNAs in less than 40 million reads for the first time from the Nicotiana benthamiana whose genome has not been fully annotated. Supported by the PCR-based validation and Sanger sequencing of selective circRNAs, our method represents a valuable tool in profiling circRNAs from the organisms with or without genome annotation.

TGF-ß promotes fibrosis after severe acute kidney injury by enhancing renal macrophage infiltration.

TGF-ß signals through a receptor complex composed of 2 type I and 2 type II (TGF-ßRII) subunits. We investigated the role of macrophage TGF-ß signaling in fibrosis after AKI in mice with selective monocyte/macrophage TGF-ßRII deletion (macrophage TGF-ßRII-/- mice). Four weeks after injury, renal TGF-ß1 expression and fibrosis were higher in WT mice than macrophage TGF-ßRII-/- mice, which had decreased renal macrophages. The in vitro chemotactic response to f-Met-Leu-Phe was comparable between bone marrow-derived monocytes (BMMs) from WT and macrophage TGF-ßRII-/- mice, but TGF-ßRII-/- BMMs did not respond to TGF-ß. We then implanted Matrigel plugs suffused with either f-Met-Leu-Phe or TGF-ß1 into WT or macrophage TGF-ßRII-/- mice. After 6 days, f-Met-Leu-Phe induced similar macrophage infiltration into the Matrigel plugs of WT and macrophage TGF-ßRII-/- mice, but TGF-ß induced infiltration only in WT mice. We further determined the number of labeled WT or TGF-ßRII-/- BMMs infiltrating into WT kidneys 20 days after ischemic injury. There were more labeled WT BMMs than TGF-ßRII-/- BMMs. Therefore, macrophage TGF-ßRII deletion protects against the development of tubulointerstitial fibrosis following severe ischemic renal injury. Chemoattraction of macrophages to the injured kidney through a TGF-ß/TGF-ßRII axis is a heretofore undescribed mechanism by which TGF-ß can mediate renal fibrosis during progressive renal injury.

AQP9 promotes astrocytoma cell invasion and motility via the AKT pathway.

The aquaporin (AQP) family, which includes 13 members identified in mammalian cells, is involved in cancer development and progression. AQP9 expression is upregulated in several tumor tissue types. However, the functions of AQP9 in astrocytoma remain elusive. The present study identified that AQP9 was expressed in astrocytoma cells. AQP9 expression was silenced by transfection with small interfering RNAs and increased by transfection with a plasmid containing the AQP9 gene. Using invasion and wound-healing assays, it was revealed that the knockdown of AQP9 suppressed astrocytoma cell invasion and motility, whereas overexpression of AQP9 promoted the invasion and motility of astrocytoma cells. It was further revealed that AQP9 could induce RAC serine/threonine-protein kinase (AKT) activation and decrease E-cadherin expression in astrocytoma cells. Inhibition of the AKT pathway attenuated AQP9-mediated invasion, motility and E-cadherin expression. Taken together, the results of the present study indicated that AQP9 promoted the invasion and motility of cells via the AKT pathway. Therefore, AQP9 may represent a potential target for therapeutic use of astrocytoma.

Inhibition of Epidermal Growth Factor Receptor Activation Is Associated With Improved Diabetic Nephropathy and Insulin Resistance in Type 2 Diabetes.

Previous studies by us and others have indicated that renal epidermal growth factor receptors (EGFR) are activated in models of diabetic nephropathy (DN) and that inhibition of EGFR activity protects against progressive DN in type 1 diabetes. In this study we examined whether inhibition of EGFR activation would affect the development of DN in a mouse model of accelerated type 2 diabetes (BKS db/db with endothelial nitric oxide knockout [eNOS-/-db/db]). eNOS-/-db/db mice received vehicle or erlotinib, an inhibitor of EGFR tyrosine kinase activity, beginning at 8 weeks of age and were sacrificed at 20 weeks of age. In addition, genetic models inhibiting EGFR activity (waved 2) and transforming growth factor-α (waved 1) were studied in this model of DN in type 2 diabetes. Compared with vehicle-treated mice, erlotinib-treated animals had less albuminuria and glomerulosclerosis, less podocyte loss, and smaller amounts of renal profibrotic and fibrotic components. Erlotinib treatment decreased renal oxidative stress, macrophage and T-lymphocyte infiltration, and the production of proinflammatory cytokines. Erlotinib treatment also preserved pancreas function, and these mice had higher blood insulin levels at 20 weeks, decreased basal blood glucose levels, increased glucose tolerance and insulin sensitivity, and increased blood levels of adiponectin compared with vehicle-treated mice. Similar to the aforementioned results, both waved 1 and waved 2 diabetic mice also had attenuated DN, preserved pancreas function, and decreased basal blood glucose levels. In this mouse model of accelerated DN, inhibition of EGFR signaling led to increased longevity.

Effects of microRNA-26b on proliferation and invasion of glioma cells and related mechanisms.

Neuroglioma is the most common primary malignant tumor in neurosurgery. Due to its short survival period and high patient mortality rate, neuroglioma is a major challenge in clinics. Elucidating the pathogenic mechanisms and associated molecular targets of neuroglioma can therefore benefit diagnosis and treatment of glioma. Previous studies have established the role of microRNA (miR)­26b in various tumors, including breast cancer, lymphoma and glioma. Its function and mechanism in neuroglioma, however, remains to be elucidated. In the present study, in vitro cultured U87 glioma cells were randomly divided into miR­26b mimic, miR­26b inhibitor and respective control (NC) groups. MTT assay was performed to detect the effect of miR­26b on cell proliferation, while a cell invasion assay detected its effects on cell invasion. Caspase­3 activity was also quantified to test cell apoptosis, followed by reverse transcription-quantitative polymerase chain reaction and western blotting to detect the variation of Bcl­2 expression under the effect of miR­26b. miR­26b mimics transfection upregulated its expression in U87 cells, which had significantly reduced Bcl­2 mRNA and protein expression levels and higher casapse3 activity, and inhibited cell proliferation and invasion compared with the control group. The transfection of miR­26b inhibitor, in contrast, facilitated U87 cell proliferation and invasion, inhibited caspase­3 activity and elevated Bcl­2 mRNA/protein expression. In conclusion, miR­26 could facilitate apoptosis and inhibit proliferation/invasion of neuroglioma cells via downregulating Bcl­2 expression and potentiating caspase-3 activity.

Template-dependent multiple displacement amplification for profiling human circulating RNA.

Multiple displacement amplification (MDA) is widely used in whole-genome/transcriptome amplification. However, template-independent amplification (TIA) in MDA is a commonly observed phenomenon, particularly when using high concentrations of random hexamer primers and extended incubation times. Here, we demonstrate that the use of random pentamer primers with 5´ ends blocked by a C18 spacer results in MDA solely in a template-dependent manner, a technique we have named tdMDA. Together with an optimized procedure for the removal of residual genomic DNA during RNA extraction, tdMDA was used to profile circulating RNA from 0.2 mL of patient sera. In comparison to regular MDA, tdMDA demonstrated a lack of quantifiable DNA amplification in the negative control, a remarkable reduction of unmapped reads from Illumina sequencing (7 ± 10.9% versus 58.6 ± 39%, P = 0.006), and increased mapping rates of the serum transcriptome (26.9 ± 7.9% versus 5.8 ± 8.2%, P = 3.8 × 10-4). Transcriptome profiles could be used to separate patients with chronic hepatitis C virus (HCV) infection from those with HCV-associated hepatocellular carcinoma (HCC). We conclude that tdMDA should facilitate RNA-based liquid biopsy, as well as other genome studies with biological specimens having ultralow amounts of genetic material.

Macrophage Cyclooxygenase-2 Protects Against Development of Diabetic Nephropathy.

Diabetic nephropathy (DN) is characterized by increased macrophage infiltration, and proinflammatory M1 macrophages contribute to development of DN. Previous studies by us and others have reported that macrophage cyclooxygenase-2 (COX-2) plays a role in polarization and maintenance of a macrophage tissue-reparative M2 phenotype. We examined the effects of macrophage COX-2 on development of DN in type 1 diabetes. Cultured macrophages with COX-2 deletion exhibited an M1 phenotype, as demonstrated by higher inducible nitric oxide synthase and nuclear factor-κB levels but lower interleukin-4 receptor-α levels. Compared with corresponding wild-type diabetic mice, mice with COX-2 deletion in hematopoietic cells (COX-2 knockout bone marrow transplantation) or macrophages (CD11b-Cre COX2f/f) developed severe DN, as indicated by increased albuminuria, fibrosis, and renal infiltration of T cells, neutrophils, and macrophages. Although diabetic kidneys with macrophage COX-2 deletion had more macrophage infiltration, they had fewer renal M2 macrophages. Diabetic kidneys with macrophage COX-2 deletion also had increased endoplasmic reticulum stress and decreased number of podocytes. Similar results were found in diabetic mice with macrophage PGE2 receptor subtype 4 deletion. In summary, these studies have demonstrated an important but unexpected role for macrophage COX-2/prostaglandin E2/PGE2 receptor subtype 4 signaling to lessen progression of diabetic kidney disease, unlike the pathogenic effects of increased COX-2 expression in intrinsic renal cells.

Inhibition of cyclooxygenase-2 in hematopoietic cells results in salt-sensitive hypertension.

Inhibition of prostaglandin (PG) production with either nonselective or selective inhibitors of cyclooxygenase-2 (COX-2) activity can induce or exacerbate salt-sensitive hypertension. This effect has been previously attributed to inhibition of intrinsic renal COX-2 activity and subsequent increase in sodium retention by the kidney. Here, we found that macrophages isolated from kidneys of high-salt-treated WT mice have increased levels of COX-2 and microsomal PGE synthase-1 (mPGES-1). Furthermore, BM transplantation (BMT) from either COX-2-deficient or mPGES-1-deficient mice into WT mice or macrophage-specific deletion of the PGE2 type 4 (EP4) receptor induced salt-sensitive hypertension and increased phosphorylation of the renal sodium chloride cotransporter (NCC). Kidneys from high-salt-treated WT mice transplanted with Cox2-/- BM had increased macrophage and T cell infiltration and increased M1- and Th1-associated markers and cytokines. Skin macrophages from high-salt-treated mice with either genetic or pharmacologic inhibition of the COX-2 pathway expressed decreased M2 markers and VEGF-C production and exhibited aberrant lymphangiogenesis. Together, these studies demonstrate that COX-2-derived PGE2 in hematopoietic cells plays an important role in both kidney and skin in maintaining homeostasis in response to chronically increased dietary salt. Moreover, these results indicate that inhibiting COX-2 expression or activity in hematopoietic cells can result in a predisposition to salt-sensitive hypertension.

Prostaglandin E receptor 4 (EP4) promotes colonic tumorigenesis.

Colorectal cancer (CRC) continues to be a major cause of morbidity and mortality. Although the factors underlying CRC development and progression are multifactorial, there is an important role for tumor-host interactions, especially interactions with myeloid cells. There is also increasing evidence that cyclooxygenase-derived prostaglandins are important mediators of CRC development and growth. Although prevention trials with either nonselective NSAIDs or COX-2 selective agents have shown promise, the gastrointestinal or cardiovascular side effects of these agents have limited their implementation. The predominant prostaglandin involved in CRC pathogenesis is PGE2. Since myeloid cells express high levels of the PGE2 receptor subtype, EP4, we selectively ablated EP4 in myeloid cells and studied adenoma formation in a mouse model of intestinal adenomatous polyposis, ApcMin/+ mice. ApcMin/+mice with selective myeloid cell deletion of EP4 had marked inhibition of both adenoma number and size, with associated decreases in mTOR and ERK activation. Either genetic or pharmacologic inhibition of EP4 receptors led to an anti-tumorigenic M1 phenotype of macrophages/dendritic cells. Therefore, PGE2-mediated EP4 signaling in myeloid cells promotes tumorigenesis, suggesting EP4 as a potentially attractive target for CRC chemoprevention or treatment.