Phenotypic Characterization of Macrophages from Rat Kidney by Flow Cytometry

Macrophage polarization involved the inflammation of chronic obstructive pulmonary disease by S1P/HDAC1 signaling

Globally, chronic obstructive pulmonary disease (COPD) is the cause of high morbidity and mortality, and constitutes a huge public health burden. Previous studies have reported that inflammation is closely related to COPD, but its potential mechanism is still unclear. Since the polarization of macrophages is involved in regulating inflammation, we assume that COPD changes the polarization of macrophages. To verify this, we investigated the relationship between the expression of S1PR1, HADC1, and inflammatory macrophages in COPD patients via flow cytometry, qRT-PCR, and western blot analysis. We found that macrophages of COPD individuals differentiated into M1 phenotype, and the expression of S1PR1 increased and HDAC1 decreased. S1PR1 also inhibits the expression of HDAC1, so S1PR1/HDAC1 signal regulates the polarization of macrophages. The results of the study put forward new ideas of the pathogenesis of COPD, and also proposed the possible treatment options.

New experimental model of kidney injury: Photothrombosis-induced kidney ischemia

Acute kidney injury (AKI) is a frequent pathology with a high mortality rate after even a single AKI episode and a great risk of chronic kidney disease (CKD) development. To get insight into mechanisms of the AKI pathogenesis, there is a need to develop diverse experimental models of the disease. Photothrombosis is a widely used method for inducing ischemia in the brain. In this study, for the first time, we described photothrombosis-induced kidney ischemia as an appropriate model of AKI and obtained comprehensive characteristics of the photothrombotic lesion using micro-computed tomography (micro-CT) and histological techniques. In the ischemic area, we observed destruction of tubules, the loss of brush border and nuclei, connective tissue fibers disorganization, leukocyte infiltration, and hyaline casts formation. In kidney tissue and urine, we revealed increased levels in markers of proliferation and injury. The explicit long-term consequence of photothrombosis-induced kidney ischemia was renal fibrosis. Thus, we establish a new low invasive experimental model of AKI, which provides a reproducible local ischemic injury lesion. We propose our model of photothrombosis-induced kidney ischemia as a useful approach for investigating AKI pathogenesis, studying the mechanisms of kidney regeneration, and development of therapy against AKI and CKD.

Low-Intensity Focused Ultrasound Ameliorates Ischemic Heart Failure Related to the Cholinergic Anti-Inflammatory Pathway

OBJECTIVES

This study aims to determine the effect of low-intensity focused ultrasound (LIFU) in ischemic heart failure (IHF) and explore the potential neuroimmune mechanism.

METHODS

Sprague-Dawley rats were subjected to ultrasound (US) with specific parameters, and electrocardiograms were recorded to analyze the effect of LIFU and/or vagal denervation on heart rate. Thereafter, myocardial infarction (MI) was induced by left anterior artery ligation, and LIFU was performed three times a day for 25 days after MI. Echocardiography, Masson staining, and ELISA were used to evaluate the effect of LIFU on the structure and function of the heart. Finally, ELISA, flow cytometry, qRT-PCR, and Western blot analysis were performed to determine the effect of LIFU on the inflammation and the expression of the cholinergic anti-inflammatory pathway (CAP)-related mediators.

RESULTS

LIFU reduced heart rate in rats (control vs LIFU, P < .01), and vagotomy (VT) eliminated this effect of LIFU on heart rate (VT vs LIFU + VT, P > .01). LIFU-ameliorated IHF in terms of cardiac structure and function (MI vs MI + LIFU, P < .01), but VT abrogated the beneficial effect of LIFU (MI + VT vs MI + LIFU + VT, P > .01). After the treatment of LIFU, decreased levels of inflammatory cytokines, increased proportion of anti-inflammatory macrophages, and increased expression of CAP-related mediators (MI vs MI + LIFU, P < .01).

CONCLUSIONS

LIFU ameliorates IHF whereas the CAP plays a promising role. LIFU has the potential to be a novel nonpharmacological and noninvasive therapy for the treatment of coronary artery disease and other cardiovascular diseases.

A nanofiber-hydrogel composite improves tissue repair in a rat model of Crohn's disease perianal fistulas

Perianal fistulas (PAFs) represent a severe complication of Crohn's disease (CD). Despite the advent of biologic and small-molecule therapeutics for luminal disease, PAFs in CD (CD-PAF) are relatively resistant to treatment, with less than 50% responding to any therapy. We report an injectable, biodegradable, mechanically fragmented nanofiber-hydrogel composite (mfNHC) loaded with adipose-derived stem cells (ADSCs) for the treatment of fistulas in a rat model of CD-PAF. The ADSC-loaded mfNHC results in a higher degree of healing when compared to surgical treatment of fistulas, which is a standard treatment. The volume of fistulas treated with mfNHC is decreased sixfold compared to the surgical treatment control. Molecular studies reveal that utilization of mfNHC reduced local inflammation and improved tissue regeneration. This study demonstrates that ADSC-loaded mfNHC is a promising therapy for CD-PAF, and warrants further studies to advance mfNHC toward clinical translation.

Auriculotherapy Modulates Macrophage Polarization to Reduce Inflammatory Response in a Rat Model of Acne

Background

The inflammatory response is an important part of the pathogenesis of acne vulgaris. Auriculotherapy has been shown to have a good therapeutic effect on this disease. The aim of this study was to explore the mechanism underlying the anti-inflammatory effect of auriculotherapy in the treatment of acne vulgaris.

Methods

Propionibacterium acnes was injected subcutaneously into the ears of rats to establish an animal model of acne. The auriculotherapy intervention in rats consisted of auricular bloodletting therapy (ABT), auricular point sticking (APS), or a combination of both (ABPS). The anti-inflammatory effects of auriculotherapy were evaluated by measuring changes in ear thickness, local body surface microcirculation in the ear, and serum inflammatory factors in rats. The polarization of macrophages was analyzed by flow cytometry, and the expression of TLR2/NF-κB signaling pathway in the target tissues was analyzed using western blot.

Results

ABT, APS, and ABPS all reduced the erythema of ear acne, decreased microcirculation in localized ear acne, and decreased serum levels of TNF-α and IL-1β in rats. Meanwhile, the three interventions reduced M1-type macrophages and increased M2-type macrophages; only APS could reduce the expression of TLR2/NF-κB signaling pathway.

Conclusion

ABT, APS, and ABPS can improve the inflammatory symptoms of acne and reduce inflammatory cytokines. APS may exert anti-inflammatory effects by altering macrophage polarization and decreasing TLR2/NF-κB expression.

Phagocytosing differentiated cell-fragments is a novel mechanism for controlling somatic stem cell differentiation within a short time frame

Stem cells undergo cytokine-driven differentiation, but this process often takes longer than several weeks to complete. A novel mechanism for somatic stem cell differentiation via phagocytosing ‘model cells’ (apoptotic differentiated cells) was found to require only a short time frame. Pluripotent-like Muse cells, multipotent mesenchymal stem cells (MSCs), and neural stem cells (NSCs) phagocytosed apoptotic differentiated cells via different phagocytic receptor subsets than macrophages. The phagocytosed-differentiated cell-derived contents (e.g., transcription factors) were quickly released into the cytoplasm, translocated into the nucleus, and bound to promoter regions of the stem cell genomes. Within 24 ~ 36 h, the cells expressed lineage-specific markers corresponding to the phagocytosed-differentiated cells, both in vitro and in vivo. At 1 week, the gene expression profiles were similar to those of the authentic differentiated cells and expressed functional markers. Differentiation was limited to the inherent potential of each cell line: triploblastic-, adipogenic-/chondrogenic-, and neural-lineages in Muse cells, MSCs, and NSCs, respectively. Disruption of phagocytosis, either by phagocytic receptor inhibition via small interfering RNA or annexin V treatment, impeded differentiation in vitro and in vivo. Together, our findings uncovered a simple mechanism by which differentiation-directing factors are directly transferred to somatic stem cells by phagocytosing apoptotic differentiated cells to trigger their rapid differentiation into the target cell lineage.

Snapshots of nascent RNA reveal cell- and stimulus-specific responses to acute kidney injury

The current strategy to detect acute injury of kidney tubular cells relies on changes in serum levels of creatinine. Yet serum creatinine (sCr) is a marker of both functional and pathological processes and does not adequately assay tubular injury. In addition, sCr may require days to reach diagnostic thresholds, yet tubular cells respond with programs of damage and repair within minutes or hours. To detect acute responses to clinically relevant stimuli, we created mice expressing Rosa26-floxed-stop uracil phosphoribosyltransferase (Uprt) and inoculated 4-thiouracil (4-TU) to tag nascent RNA at selected time points. Cre-driven 4-TU-tagged RNA was isolated from intact kidneys and demonstrated that volume depletion and ischemia induced different genetic programs in collecting ducts and intercalated cells. Even lineage-related cell types expressed different genes in response to the 2 stressors. TU tagging also demonstrated the transient nature of the responses. Because we placed Uprt in the ubiquitously active Rosa26 locus, nascent RNAs from many cell types can be tagged in vivo and their roles interrogated under various conditions. In short, 4-TU labeling identifies stimulus-specific, cell-specific, and time-dependent acute responses that are otherwise difficult to detect with other technologies and are entirely obscured when sCr is the sole metric of kidney damage.

Macrophages Can Drive Sympathetic Excitability in the Early Stages of Hypertension

Hypertension is a major health burden worldwide with many cases resistant to current treatments. Hyperactivity of the sympathetic nervous contributes to the etiology and progression of the disease, where emerging evidence suggests that inflammation may underpin the development of sympathetic dysautonomia. This study examined whether macrophages could drive the sympathetic phenotype in Spontaneously Hypertensive Rats (SHR) before animals develop high pressure. Stellate neurons from wild-type control Wistar rats and SHRs were co-cultured with blood leukocytes from their own strain, and also crossed cultured between strains. The calcium transient response to nicotinic stimulation was recorded using Fura-2 calcium imaging, where SHR neurons had a greater calcium transient compared with Wistar neurons. However, when co-cultured with leukocytes, Wistar neurons began to phenocopy the SHR sympathetic hyperactivity, while the SHR neurons themselves were unaltered. Resident leukocyte populations of the SHR and Wistar stellate ganglia were then compared using flow cytometry, where there was a shift in monocyte-macrophage subset proportions. While classical monocyte-macrophages were predominant in the Wistar, there were relatively more of the non-classical subset in the SHR, which have been implicated in pro-inflammatory roles in a number of diseases. When bone marrow-derived macrophages (BMDMs) were co-cultured with stellate neurons, they made Wistar neurons recapitulate the SHR nicotinic stimulated calcium transient. Wistar BMDMs however, had no effect on SHR neurons, even though SHR BMDMs increased SHR neuron responsiveness further above their hyper-responsive state. Taken together, these findings show that macrophages can be potent enhancers of sympathetic neuronal calcium responsiveness, and thus could conceivably play a role in peripheral sympathetic hyperactivity observed in the early stages of hypertension.

Phosphorus Supplementation Mitigates Perivascular Adipose Inflammation-Induced Cardiovascular Consequences in Early Metabolic Impairment

Background

The complexity of the interaction between metabolic dysfunction and cardiovascular complications has long been recognized to extend beyond simple perturbations of blood glucose levels. Yet, structured interventions targeting the root pathologies are not forthcoming. Growing evidence implicates the inflammatory changes occurring in perivascular adipose tissue (PVAT) as early instigators of cardiovascular deterioration.

Methods and Results

We used a nonobese prediabetic rat model with localized PVAT inflammation induced by hypercaloric diet feeding, which dilutes inorganic phosphorus (Pi) to energy ratio by 50%, to investigate whether Pi supplementation ameliorates the early metabolic impairment. A 12‐week Pi supplementation at concentrations equivalent to and twice as much as that in the control diet was performed. The localized PVAT inflammation was reversed in a dose‐dependent manner. The increased expression of UCP1 (uncoupling protein1), HIF‐1α (hypoxia inducible factor‐1α), and IL‐1β (interleukin‐1β), representing the hallmark of PVAT inflammation in this rat model, were reversed, with normalization of PVAT macrophage polarization. Pi supplementation restored the metabolic efficiency consistent with its putative role as an UCP1 inhibitor. Alongside, parasympathetic autonomic and cerebrovascular dysfunction function observed in the prediabetic model was reversed, together with the mitigation of multiple molecular and histological cardiovascular damage markers. Significantly, a Pi‐deficient control diet neither induced PVAT inflammation nor cardiovascular dysfunction, whereas Pi reinstatement in the diet after a 10‐week exposure to a hypercaloric low‐Pi diet ameliorated the dysfunction.

Conclusions

Our present results propose Pi supplementation as a simple intervention to reverse PVAT inflammation and its early cardiovascular consequences, possibly through the interference with hypercaloric‐induced increase in UCP1 expression/activity.

Kidney resident macrophages in the rat have minimal turnover and replacement by blood monocytes

Kidney resident macrophages (KRMs) are involved in maintaining renal homeostasis and in controlling the pathological outcome of acute kidney injury and cystic kidney disease in mice. In adult mice, KRMs maintain their population through self-renewal with little or no input from the peripheral blood. Despite recent data suggesting that a transcriptionally similar population of KRM-like cells is present across species, the idea that they are self-renewing and minimally dependent on peripheral blood input in other species has yet to be proven due to the lack of an appropriate model and cross-species expression markers. In this study, we used our recently identified cross-species KRM cell surface markers and parabiosis surgery in inbred Lewis rats to determine if rat KRMs are maintained independent of peripheral blood input, similar to their mouse counterparts. Flow cytometry analysis indicated that parabiosis surgery in the rat results in the establishment of chimerism of T/B cells, neutrophils, and monocyte-derived infiltrating macrophages in the blood, spleen, and kidney 3 wk after parabiosis surgery. Analysis of KRMs using the cell surface markers CD81 and C1q indicated that these cells have minimal chimerism and, therefore, receive little input from the peripheral blood. These data indicate that KRM properties are conserved in at least two different species.NEW & NOTEWORTHY In this report, we performed parabiosis surgery on inbred Lewis rats and showed that rat kidney resident macrophages (KRMs), identified using our novel cross-species markers, are minimally dependent on peripheral blood input. Thus, for the first time, to our knowledge, we confirm that a hallmark of mouse KRMs is also present in KRMs isolated from another species.

Statins Directly Influence the Polarization of Adipose Tissue Macrophages: A Role in Chronic Inflammation

Statins represent one of the most widely used classes of drugs in current medicine. In addition to a substantial decrease in atherogenic low density lipoprotein (LDL) particle concentrations, several large trials have documented their potent anti-inflammatory activity. Based on our preliminary data, we showed that statins are able to decrease the proportion of pro-inflammatory macrophages (CD14+16+CD36high) in visceral adipose tissue in humans. In the present study including 118 healthy individuals (living kidney donors), a very close relationship between the pro-inflammatory macrophage proportion and LDL cholesterol levels was found. This was confirmed after adjustment for the most important risk factors. The effect of statins on the proportion of pro-inflammatory macrophages was also confirmed in an experimental model of the Prague hereditary hypercholesterolemia rat. A direct anti-inflammatory effect of fluvastatin on human macrophage polarization in vitro was documented. Based on modifying the LDL cholesterol concentrations, statins are suggested to decrease the cholesterol inflow through the lipid raft of macrophages in adipose tissue and hypercholesterolemia to enhance the pro-inflammatory macrophage phenotype polarization. On the contrary, due to their opposite effect, statins respond with anti-inflammatory activity, affecting the whole organism.

Intraglomerular Monocyte/Macrophage Infiltration and Macrophage-Myofibroblast Transition during Diabetic Nephropathy Is Regulated by the A2B Adenosine Receptor

Diabetic nephropathy (DN) is considered the main cause of kidney disease in which myofibroblasts lead to renal fibrosis. Macrophages were recently identified as the major source of myofibroblasts in a process known as macrophage–myofibroblast transition (MMT). Adenosine levels increase during DN and in vivo administration of MRS1754, an antagonist of the A_2B adenosine receptor (A_2BAR), attenuated glomerular fibrosis (glomerulosclerosis). We aimed to investigate the association between A_2BAR and MMT in glomerulosclerosis during DN. Kidneys/glomeruli of non-diabetic, diabetic, and MRS1754-treated diabetic (DM+MRS1754) rats were processed for histopathologic, transcriptomic, flow cytometry, and cellular in vitro analyses. Macrophages were used for in vitro cell migration/transmigration assays and MMT studies. In vivo MRS1754 treatment attenuated the clinical and histopathological signs of glomerulosclerosis in DN rats. Transcriptomic analysis demonstrated a decrease in chemokine-chemoattractants/cell-adhesion genes of monocytes/macrophages in DM+MRS1754 glomeruli. The number of intraglomerular infiltrated macrophages and MMT cells increased in diabetic rats. This was reverted by MRS1754 treatment. In vitro cell migration/transmigration decreased in macrophages treated with MRS1754. Human macrophages cultured with adenosine and/or TGF-β induced MMT, a process which was reduced by MRS1754. We concluded that pharmacologic blockade of A_2BAR attenuated some clinical signs of renal dysfunction and glomerulosclerosis, and decreased intraglomerular macrophage infiltration and MMT in DN rats.

Forced treadmill running reduces systemic inflammation yet worsens upper limb discomfort in a rat model of work-related musculoskeletal disorders

BACKGROUND

Musculoskeletal disorders can result from prolonged repetitive and/or forceful movements. Performance of an upper extremity high repetition high force task increases serum pro-inflammatory cytokines and upper extremity sensorimotor declines in a rat model of work-related musculoskeletal disorders. Since one of the most efficacious treatments for musculoskeletal pain is exercise, this study investigated the effectiveness of treadmill running in preventing these responses.

METHODS

Twenty-nine young adult female Sprague-Dawley rats were used. Nineteen were trained for 5 weeks to pull a lever bar at high force (15 min/day). Thirteen went on to perform a high repetition high force reaching and lever-pulling task for 10 weeks (10-wk HRHF; 2 h/day, 3 days/wk). From this group, five were randomly selected to undergo forced treadmill running exercise (TM) during the last 6 weeks of task performance (10-wk HRHF+TM, 1 h/day, 5 days/wk). Results were compared to 10 control rats and 6 rats that underwent 6 weeks of treadmill running following training only (TR-then-TM). Voluntary task and reflexive sensorimotor behavioral outcomes were assessed. Serum was assayed for inflammatory cytokines and corticosterone, reach limb median nerves for CD68+ macrophages and extraneural thickening, and reach limb flexor digitorum muscles and tendons for pathological changes.

RESULTS

10-wk HRHF rats had higher serum levels of IL-1α, IL-1β and TNFα, than control rats. In the 10-wk HRHF+TM group, IL-1β and TNFα were lower, whereas IL-10 and corticosterone were higher, compared to 10-wk HRHF only rats. Unexpectedly, several voluntary task performance outcomes (grasp force, reach success, and participation) worsened in rats that underwent treadmill running, compared to untreated 10-wk HRHF rats. Examination of forelimb tissues revealed lower cellularity within the flexor digitorum epitendon but higher numbers of CD68+ macrophages within and extraneural fibrosis around median nerves in 10-wk HRHF+TM than 10-wk HRHF rats.

CONCLUSIONS

Treadmill running was associated with lower systemic inflammation and moderate tendinosis, yet higher median nerve inflammation/fibrosis and worse task performance and sensorimotor behaviors. Continued loading of the injured tissues in addition to stress-related factors associated with forced running/exercise likely contributed to our findings.

Human mesenchymal stromal cells ameliorate complement induced inflammatory cascade and improve renal functions in a rat model of ischemia-reperfusion induced acute kidney injury

Introduction

The primary rational for using mesenchymal stromal cells (MSCs) to rejuvenate damaged tissue is mostly based on their capacity to trans-differentiate and repair injured organs. However, previous studies have demonstrated that MSCs are beneficial even at very early stages, before differentiation and proliferation can be expected. The aim of the current study was to investigate the multifaceted immunological effects of systemically administrating MSCs in the setting of acute kidney injury (AKI) induced by ischemic-reperfusion (I/R).

Methods

A rat model of I/R induced AKI was used. The rats underwent a unilateral nephrectomy with simultaneously clamping the contralateral kidney for 60 minutes. Four treatment groups received intravenously, increasing doses of human MSCs and after 48 hours, the rats were sacrificed. Blood was taken to evaluate renal functions and to measure systemic inflammatory markers. Kidneys were taken for histopathologic examinations and evaluations of intra-renal complement activation and inflammatory mediators.

Results

Renal functions improved in U shaped dose dependent manner. Mean serum creatinine levels were 4.5, 2.9, 2.6, 1.7 and 4.1 mg/dL in I/R + placebo, I/R + 150x10³ cells, I/R + 250x10³ cells, I/R + 500x10³ cells and I/R + 1,000x10³ cells respectfully (p-values<0.05). Urea demonstrated consistent results with the same U shape improvement manner. The extensive activation of the complement system was ameliorated in the MSCs treatment groups. In addition, MSCs significantly decreased intra-renal levels of IL-1β and TNF-α. It should be noted that the highest doses of MSCs induced renal hypoxia, marked by the Hypoxy-probe staining.

Conclusions

The early beneficial effect of MSCs in the setting of AKI may be attributed to their immunomodulatory effects. Safe treatment with MSCs can block the deleterious activation of the complement cascade and alleviate the hazardous inflammatory mediator-related cascade.

Salt-sensitive increase in macrophages in the kidneys of Dahl SS rats

Studies of Dahl salt-sensitive (SS) rats have shown that renal CD3⁺ T cells and ED-1⁺ macrophages are involved in the development of salt-sensitive hypertension and renal damage. The present study demonstrated that the increase in renal immune cells, which accompanies renal hypertrophy and albuminuria in high-salt diet-fed Dahl SS rats, is absent in Sprague-Dawley and SSBN13 rats that are protected from the SS disease phenotype. Flow cytometric analysis demonstrated that >70% of the immune cells in the SS kidney are M1 macrophages. PCR profiling of renal myeloid cells showed a salt-induced upregulation in 9 of 84 genes related to Toll-like receptor signaling, with notable upregulation of the Toll-like receptor 4/CD14/MD2 complex. Because of the prominent increase in macrophages in the SS kidney, we used liposome-encapsulated clodronate (Clod) to deplete macrophages and assess their contribution to salt-sensitive hypertension and renal damage. Dahl SS animals were administered either Clod-containing liposomes (Clod-Lipo), Clod, or PBS-containing liposomes as a vehicle control. Clod-Lipo treatment depleted circulating and splenic macrophages by ∼50%; however, contrary to our hypothesis, Clod-Lipo-treated animals developed an exacerbated salt-sensitive response with respect to blood pressure and albuminuria, which was accompanied by increased renal T and B cells. Interestingly, those treated with Clod also demonstrated an exacerbated phenotype, but it was less severe than Clod-Lipo-treated animals and independent of changes to the number of renal immune cells. Here, we have shown that renal macrophages in Dahl SS animals sustain a M1 proinflammatory phenotype in response to increased dietary salt and highlighted potential adverse effects of Clod-Lipo macrophage depletion.

Dissecting recipient from donor contribution in experimental kidney transplantation: focus on endothelial proliferation and inflammation

Kidney transplantation (Tx) is considered the only definite treatment for end-stage kidney disease (ESKD) patients. The increasing prevalence of ESKD has necessitated the introduction of transplantation with kidneys from suboptimal donors. There is, however, still a lack of fundamental and longitudinal research on suboptimal kidney transplants. Specifically, there is a demand for accurate pre-Tx predictors of donor kidney function and injury to predict post-Tx outcome. In the present study, we combine rat models of chronic kidney disease (CKD) and renal Tx to dissect the effects of healthy and CKD renal grafts on healthy and CKD recipients. We show that renal function at 6 weeks post-Tx is exclusively determined by donor graft quality. Using cell tracking within enhanced green fluorescent protein-positive (eGFP⁺) recipients, we furthermore show that most inflammatory cells within the donor kidney originate from the donor. Oxidative and vascular extra-renal damage were, in contrast, determined by the recipient. Post- versus pre-Tx evaluation of grafts showed an increase in glomerular and peritubular capillary rarefaction in healthy but not CKD grafts within a CKD environment. Proliferation of glomerular endothelium was similar in all groups, and influx of eGFP⁺ recipient-derived cells occurred irrespective of graft or recipient status. Glomerular and peritubular capillary rarefaction, severity of inflammation and macrophage subtype data post-Tx were, however, determined by more complicated effects, warranting further study. Our experimental model could help to further distinguish graft from recipient environment effects, leading to new strategies to improve graft survival of suboptimal Tx kidneys.

This article has an associated First Person interview with the first author of the paper.

Summary: Using experimental kidney transplantation, we dissected donor graft from recipient environment effects, focusing on the endothelium and inflammation. These results can direct strategies to improve graft survival after suboptimal transplantation.

Abdominal surgery induced gastric ileus and activation of M1-like macrophages in the gastric myenteric plexus: prevention by central vagal activation in rats

Inflammation plays a role in abdominal surgery (AS)-induced intestinal ileus that is alleviated by electrical vagal stimulation. Intracisternal injection of RX-77368, the stable thyrotropin-releasing hormone agonist, activates dorsal motor nucleus neurons and gastric vagal efferent discharges. We investigated the gastric inflammation induced by AS and the modulation by intracisternal RX-77368 in rats. RX-77368 (50 ng/rat) or saline was injected followed, 1 h later, by laparotomy and small intestinal/cecal manipulation. The sham group had anesthesia alone. After 6 h, gastric emptying (GE) and the inflammation in gastric corpus were determined. AS inhibited GE by 72% vs. control and doubled the number of M1-like macrophage immunoreactive for major histocompatibility complex class II (MHCII; M1 marker) but not for cluster of differentiation 206 (CD206; M2 marker) (MHCII⁺/CD206^-) while there was no change in M2-like macrophages (MHCII^-/CD206⁺). AS increased mRNA levels of interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α) by 1.7- and 1.5-fold, respectively, in the gastric submucosa plus muscle layers and the infiltration of neutrophils labeled by myeloperoxidase by 9.5-fold in the muscularis externa. RX-77368 inhibited AS-related gastric changes while not altering these parameters in the sham group. There was a significant negative correlation between GE and IL-1β (r = -0.46), TNF-α (r = -0.44), M1 macrophage (r = -0.82), and neutrophils (r = -0.91). The M2-like macrophages and IL-10 expression were unchanged by AS with intracisternal saline or RX-77368. These data indicate that AS activates gastric M1 macrophages and increases proinflammatory cytokines expression, which are prevented by central vagal activation and may contribute to the correlated dampening of postoperative gastric ileus.NEW & NOTEWORTHY MHCII⁺/CD206^- (M1) and MHCII^-/CD206⁺ (M2) constitute two distinct populations of macrophages that are in close apposition to the cholinergic neurons in the rat gastric myenteric plexus (MP). Abdominal surgery (6 h) activates M1 macrophage leading to inflammation in the gastric MP correlated with the delayed gastric emptying, which was abolished by central vagal stimulation via intracisternal injection of RX-77368. Vagal stimulation linked with the cephalic phase may have potential beneficial effects to curtail postoperative gastric ileus.

Preparation of exenatide-loaded linear poly(ethylene glycol)-brush poly(l-lysine) block copolymer: potential implications on diabetic nephropathy

The poly(ethylene glycol)-b-brush poly(l-lysine) polymer (PEG-b-(PELG50-g-PLL3)) was synthesized and evaluated as a nanocarrier for prolonging delivery of exenatide through the abdominal subcutaneous injection route. The isoelectric point of exenatide was 4.86, and exenatide could combine with PEG-b-(PELG50-g-PLL3) polymers via electrostatic interactions at pH 7.4. This polymer was a good candidate for achieving prolonged drug delivery for exenatide, considering its high molecular weight. Besides the physicochemical characterization of the polymer, in vitro and in vivo applications were researched as a sustained exenatide delivery system. In the in vitro release research, 20.16%-76.88% of total exenatide was released from the PEG-b-(PELG50-g-PLL3) polymer within 7 days. The synthesized block-brush polymers and exenatide-block-brush polymers were analyzed by nuclear magnetic resonance spectroscopy, gel permeation chromatography, transmission electron microscopy, nanoparticle size instrument, and scanning electron microscopy. The best formulation was selected for in vivo experimentation to achieve blood glucose control in diabetic rat models using free exenatide as the control. The hypoglycemic action of the formulation following subcutaneous injection in diabetic rats lasted 7 days, and the results indicated that exenatide-block-brush polymers demonstrate enhanced long-acting hypoglycemic action. Besides the hypoglycemic action, exenatide-block-brush polymers significantly alleviated diabetic nephropathy via improving renal function, decreasing oxidative stress injury, decreasing urinary albumin excretion rate, mitigating albumin/creatinine ratio, reducing blood lipids, abating kidney index, weakening apoptosis, and downregulating expression of connective tissue growth factor. All of the results suggested that PEG-b-(PELG50-g-PLL3) polymers could be used as potential exenatide nanocarriers, with efficient encapsulation and sustained release.

Bronchoalveolar Lavage of Murine Lungs to Analyze Inflammatory Cell Infiltration

Bronchoalveolar Lavage (BAL) is an experimental procedure that is used to examine the cellular and acellular content of the lung lumen ex vivo to gain insight into an ongoing disease state. Here, a simple and efficient method is described to perform BAL on murine lungs without the need of special tools or equipment. BAL fluid is isolated by inserting a catheter in the trachea of terminally anesthetized mice, through which a saline solution is instilled into the bronchioles. The instilled fluid is gently retracted to maximize BAL fluid retrieval and to minimize shearing forces. This technique allows the viability, function, and structure of cells within the airways and BAL fluid to be preserved. Numerous techniques may be applied to gain further understanding of the disease state of the lung. Here, a commonly used technique for the identification and enumeration of different types of immune cells is described, where flow cytometry is combined with a select panel of fluorescently labeled cell surface-specific markers. The BAL procedure presented here can also be used to analyze infectious agents, fluid constituents, or inhaled particles within murine lungs.