Introduction: Forum in immunology on neutrophils

Therapeutic effects of pentoxifylline on invasive pulmonary aspergillosis in immunosuppressed mice

Background

The most common and severe infection of Aspergillus fumigatus is invasive pulmonary aspergillosis (IPA), which is usually seen in immunocompromised patients. Neutropenia is the primary risk factor implicated in IPA; however, IPA also occurs in patients without neutropenia, namely, those who are immunosuppressed owing to long-term corticosteroid use. With IPA-associated mortality as high as 51–79%, novel and effective treatment strategies are urgently needed. Pentoxifylline (PTX) has been shown to competitively inhibit the family 18 chitinases in fungi, which may be an new antifungal therapy. Hence, the aim of our study was to compare neutropenic and non-neutropenic IPA mouse models, and to evaluate the effect of PTX on IPA in immunosuppressed mice.

Methods

C57BL/6J mice were pre-treated with cyclophosphamide and hydrocortisone. Neutropenic model IPA mice (CTX-IPA) and non-neutropenic IPA mice (HC-IPA) were established by intranasal administration of Aspergillus fumigatus spore suspension. A subset of each group was injected with PTX post-infection. Among these groups, we compared overall survival, pulmonary fungal burden, lung hispathology, and myeloperoxidase (MPO), interleukin 8 (IL-8), and mammalian chitinase concentration in the bronchoalveolar lavage fluid (BALF).

Results

The survival rate of the HC-IPA group was higher than that of the CTX-IPA group, and pulmonary fungal burden was also lower (p < 0.05). The CTX-IPA group showed infiltration of alveolae and blood vessels by numerous hyphae of A. fumigatus. The HC-IPA group exhibited destruction of bronchi, expansion of alveolar septa, increased macrophages aggregation, significant neutrophil infiltration and a few hyphae in peribronchial areas. After PTX treatment, improvement was observed in survival duration and pulmonary fungal burden in HC-IPA mice. MPO and IL-8 levels were lower in the HC-IPA + PTX group compared to the corresponding levels in the HC-IP group. Chitotriosidase (CHIT1) and Chitinase 3-like 1 (CHI3L1) expression in the HC-IPA group was decreased after PTX treatment (p < 0.05).

Conclusion

PTX was found to exert a therapeutic effect in a non-neutropenic mouse model of IPA, which may lead to the development of novel strategies for IPA treatment.

A Comparative Review of Equine SIRS, Sepsis, and Neutrophils

The most recent definition of sepsis in human medicine can be summarized as organ dysfunction caused by a dysregulated host response to infection. In equine medicine, although no consensus definition is available, sepsis is commonly described as a dysregulated host systemic inflammatory response to infection. Defense against host infection is the primary role of innate immune cells known as neutrophils. Neutrophils also contribute to host injury during sepsis, making them important potential targets for sepsis prevention, diagnosis, and treatment. This review will present both historical and updated perspectives on the systemic inflammatory response (SIRS) and sepsis; it will also discuss the impact of sepsis on neutrophils, and the impact of neutrophils during sepsis. Future identification of clinically relevant sepsis diagnosis and therapy depends on a more thorough understanding of disease pathogenesis across species. To gain this understanding, there is a critical need for research that utilizes a clearly defined, and consistently applied, classification system for patients diagnosed with, and at risk of developing, sepsis.

Neutrophils influx and proinflammatory cytokines inhibition by sodium salicylate, unlike aspirin, in Candida albicans-induced peritonitis model

Sodium salicylate (NaS) and aspirin (ASA) are known to have a variety of effects on microorganisms, such as fungus (C. albicans and C. neoformans), moreover, it have effects in leukocyte adhesion and migration in vitro. In this report, we investigated the effect of ASA and NaS in neutrophil migration and cytokine production in C. albicans-induced peritonitis murine model. For this, mice were treated intraperitoneally (i.p) or orally (po) with NaS or ASA; after they were stimulated i.p. with C. albicans, the cellular migration was evaluated 24 h after stimulation. NaS, in mice treated i.p., unlike ASA, was able to inhibit the neutrophil migration and proinflammatory cytokine production induced by C. albicans, such as TNF-α, IL-1, IFN-γ, IL-12, and IL-10, but did not alter the IL-4 levels in these animals. However, the po treatment with same the dose of NaS or ASA did not affect the influx of this cell for inflammatory site. These results suggest that the NaS inhibits cellular migration and proinflammatory cytokine by different anti-inflammatory mechanism compared to ASA.

Elevated levels of the neutrophil chemoattractant pro-platelet basic protein in macrophages from individuals with chronic and allergic aspergillosis

BACKGROUND

Aspergillus fumigatus causes chronic cavitary pulmonary aspergillosis (CCPA) and allergic bronchopulmonary aspergillosis (ABPA) in overtly immunocompetent and atopic individuals, respectively. Disease mechanisms are poorly understood but may be related to increased neutrophil presence and activation. Pro-platelet basic protein (PPBP) is a potent neutrophil chemoattractant and activator whose expression is repressed by interleukin 10 (IL-10).

METHODS

PPBP expression by monocyte-derived macrophages from patients with ABPA or CCPA and asthmatic and healthy controls (10 individuals per group) was analyzed using reverse-transcription polymerase chain reaction. PPBP and IL-10 protein levels in cell culture supernatants were measured by enzyme-linked immunosorbent assay. Two PPBP single-nucleotide polymorphisms (SNPs) were genotyped in 638 individuals. The gene was resequenced in 20 individuals.

RESULTS

PPBP expression and protein levels were significantly increased in the ABPA (19.7-fold) and CCPA (27.7-fold) groups, compared with the control groups. PPBP SNPs were not associated with disease. IL-10 protein levels were significantly lower in the ABPA and CCPA groups, compared with the healthy group, suggesting that differences in PPBP levels may result from regulatory mechanisms.

CONCLUSIONS

The results suggest a role for increased PPBP expression in ABPA and CCPA. Repression of PPBP expression may benefit some patients. Increased PPBP expression in ABPA and CCPA may be useful as a future diagnostic tool or possible target for novel therapeutics.

Type 2 diabetes mellitus, resistance training, and innate immunity: is there a common link?

Type 2 diabetes mellitus is a serious chronic disease that is very prevalent in the developed world. The etiology of this disease is not well understood. Recently, the role of the innate immune system in the pathogenesis of type 2 diabetes and its complications has received a great deal of attention. Cytokines, acute phase proteins, and phagocytes have been implicated in this model. Resistance training has known benefits in type 2 diabetic patients and older adults, such as improved insulin action, insulin sensitivity, fasting blood glucose and insulin, and glucose tolerance levels. Actions of pro-inflammatory mediators linked to dysregulated innate immune activity have been associated with type 2 diabetes. The immunomodulatory effects of exercise, and in particular approaches such as resistance training, may provide a strategy to counter these pro-inflammatory effectors. However, the effects of resistance training on innate immunity have not been studied extensively in adults with type 2 diabetes or in older adults who are at increased risk for development of type 2 diabetes. This review discusses the possibility that resistance training may have positive effects on innate immunity in this population and so may provide benefits in addition to improving strength and functional abilities. In particular, the potential of resistance training to modulate pro-inflammatory parameters associated with type 2 diabetes, as a strategy that could provide multiple beneficial health outcomes, is addressed.

The contribution of PARs to inflammation and immunity to fungi

During inflammation, host- and microbial-derived proteases trigger the activation of protease-activated receptors (PARs), a family of G-protein-coupled receptors. We report here that activation of Toll-like receptors (TLRs) by fungi unmasks an essential and divergent role for PAR(1) and PAR(2) in downstream signaling and inflammation. TLRs activated PARs and triggered distinct signal transduction pathways involved in inflammation and immunity to Candida albicans and Aspergillus fumigatus. Inflammation was promoted by PAR(1) and PAR(2) activation in response to Candida and by PAR(2) inhibition in response to Aspergillus. This occurred by TLR regulation of PAR signaling, with TLR2 promoting PAR(1) activity, and TLR4 suppressing PAR(2) activity. Thus, tissue injury and pathogens induce signals that are integrated at the level of distinct TLR/PAR-dependent pathways, the exploitation or subversion of which contributes to divergence in microbial promotion of inflammatory response.

Response to genistein: Assaying the activation status and chemotaxis efficacy of isolated neutrophils

Neutrophil (PMN) activation and chemotaxis toward inflammatory stimuli play critical roles in host defense and tissue inflammation. To determine the molecular mechanisms that regulate PMN function, many studies currently employ in vitro PMN activation and transmigration assays using freshly isolated peripheral PMN or PMN isolated from bone marrow. However, due to the highly sensitive nature of PMN, cell activation or priming can occur during isolation, which demands assay(s) that ensure the consistency of isolated PMN prior to using them in subsequent experiments. Here, we introduce a simple screening assay based on the observation that in transmigration assays, isolated PMN differentially respond to the tyrosine kinase inhibitor genistein and this is related to their activation status. As shown, we observed that isolated PMN for which early migration is enhanced by genistein have an overall high transmigration efficacy and that over 80% of applied PMN migrate across collagen-coated filters in a 2 h time period. Conversely, the inhibitory/non-enhancement effect of genistein is accompanied by a poor PMN transmigration, with less than 25% of applied PMN transmigrating across. Further analysis of PMN spontaneous adhesion, degranulation and cell surface CD11b/CD18 expression suggests that reduced migration of PMN is associated with PMN activation/priming that happens, in most cases, during the in vitro cell isolation procedure regardless of the blood donor. Thus, based on these observations, we developed a "genistein assay" to directly predict PMN status after each isolation. From our experience, this assay has not only revealed new insights into the mechanisms of PMN activation and assisted in functional assays, but it has also provided a method that can be mastered by both inexperienced and experienced researchers to assay isolated PMN and thus avoid using inconsistent cells (e.g. pre-activated PMN) in their experiments.

Professional phagocytic granulocytes of the bony fish gilthead seabream display functional adaptation to testicular microenvironment

It has been shown previously that professional phagocytic granulocytes are present in the testis of the gilthead seabream, a seasonal breeding teleost that offers an excellent model for studying the testicular regression process that occurs in seasonal testicular involution and sex change. It is unexpected that testicular granulocytes produce interleukin-1beta, a regulator for spermatogonia proliferation in mammals, but are not involved in the elimination of degenerative germ cells. Here, we show that phagocytosis and reactive oxygen intermediate (ROI) production were suppressed dramatically in testicular phagocytic granulocytes, compared with their level of activity in the head-kidney, the main hematopoietic organ in fish. Furthermore, testicular-conditioned media modulated migration, phagocytosis, and ROI production of head-kidney phagocytic granulocytes, and the addition of testicular cells impaired their ROI production capacity. Until now, monocytes/macrophages were believed to be the only innate immune cells able to develop into functional subsets, whereas neutrophils only infiltrate the tissues upon infection or inflammation. Our findings demonstrate, however, that fish professional phagocytic granulocytes also display functional adaptation to different microenvironments and strongly suggest a role for these cells in the reorganization of the testis during post-spawning.

Cytochemical and functional characterization of blood and inflammatory cells from the lizard Ameiva ameiva

The fine structure and differential cell count of blood and coelomic exudate leukocytes were studied with the aim to identify granulocytes from Ameiva ameiva, a lizard distributed in the tropical regions of the Americas. Blood leukocytes were separated with a Percoll cushion and coelomic exudate cells were obtained 24 h after intracoelomic thioglycollate injection. In the blood, erythrocytes, monocytes, thrombocytes, lymphocytes, plasma cells and four types of granulocytes were identified based on their morphology and cytochemistry. Types I and III granulocytes had round intracytoplasmic granules with the same basic morphology; however, type III granulocyte had a bilobued nucleus and higher amounts of heterochromatin suggesting an advance stage of maturation. Type II granulocytes had fusiformic granules and more mitochondria. Type IV granulocytes were classified as the basophil mammalian counterpart based on their morphology and relative number. Macrophages and granulocytes type III were found in the normal coelomic cavity. However, after the thioglycollate injection the number of type III granulocyte increased. Granulocytes found in the coelomic cavity were related to type III blood granulocyte based on the morphology and cytochemical localization of alkaline phosphatase and basic proteins in their intracytoplasmic granules. Differential blood leukocyte counts showed a predominance of type III granulocyte followed by lymphocyte, type I granulocyte, type II granulocyte, monocyte and type IV granulocyte. Taken together, these results indicate that types I and III granulocytes correspond to the mammalian neutrophils/heterophils and type II to the eosinophil granulocytes.

TLRs govern neutrophil activity in aspergillosis

Polymorphonuclear neutrophils (PMNs) are essential in initiation and execution of the acute inflammatory response and subsequent resolution of fungal infection. PMNs, however, may act as double-edged swords, as the excessive release of oxidants and proteases may be responsible for injury to organs and fungal sepsis. To identify regulatory mechanisms that may balance PMN-dependent protection and immunopathology in fungal infections, the involvement of different TLR-activation pathways was evaluated on human PMNs exposed to the fungus Aspergillus fumigatus. Recognition of Aspergillus and activation of PMNs occurred through the involvement of distinct members of the TLR family, each likely activating specialized antifungal effector functions. By affecting the balance between fungicidal oxidative and nonoxidative mechanisms, pro- and anti-inflammatory cytokine production, and apoptosis vs necrosis, the different TLRs ultimately impacted on the quality of microbicidal activity and inflammatory pathology. Signaling through TLR2 promoted the fungicidal activity of PMNs through oxidative pathways involving extracellular release of gelatinases and proinflammatory cytokines while TLR4 favored the oxidative pathways through the participation of azurophil, myeloperoxidase-positive, granules and IL-10. This translated in vivo in the occurrence of different patterns of fungal clearance and inflammatory pathology. Both pathways were variably affected by signaling through TLR3, TLR5, TLR6, TLR7, TLR8, and TLR9. The ability of selected individual TLRs to restore antifungal functions in defective PMNs suggests that the coordinated outputs of activation of multiple TLRs may contribute to PMN function in aspergillosis.

Proteomic survey of bovine neutrophils

Mastitis is a major economic concern for the dairy industry. Conditions such as parturition cause a transient immunosuppression that leads to increased incidence of mastitis. One facet of periparturient immunosuppression is a functional impairment of the blood and milk neutrophils in dairy cows. To better understand the biology of the bovine neutrophil we report the first proteomic analysis of the bovine neutrophil. We have identified over 250 proteins using one-dimensional electrophoresis followed by reverse-phase chromatography in line with electrospray tandem mass spectrometry. A large number of metabolic proteins were identified, including most of the enzymes required for generation of NADPH and ATP. In addition, many proteins were identified that participate in cell mobility and phagocytosis. All the bovine members of the cathelicidin family were identified, as well as other proteins with immunological functions. Proteins important for cell signaling, vesicular transport, control of apoptosis and other functions were identified giving an overview of the bovine neutrophil proteome.

Investigating the morphology, function and genetics of cytotoxic cells in bony fish

Bony fish (teleosts) possess multiple cytotoxic cell lineages that recognize and destroy virally infected and transformed cells. In general, these lineages parallel their functional equivalents in mammals and include neutrophilic granulocytes, macrophages, cytotoxic T lymphocytes (CTL) and natural killer (NK) cells. These four cell types have been morphologically identified in multiple fish species but only limited information is available about their function. In contrast, much work has gone into examining the function of a fifth cytotoxic cell lineage, termed nonspecific cytotoxic cells (NCC), that has been referred to as the bony fish equivalent of NK cells. However, evidence suggesting that NCC do not represent the NK lineage has come through the development of multiple cytotoxic catfish cell lines that are morphologically and functionally similar to human NK cells and are distinct from NCC. In addition to characterizing cytotoxic cells from fish, recent work has identified the novel immune-type receptors (NITR) and cichlid killer leukocyte receptors (cKLR) that are structurally related to mammalian NK receptors and likely play a role in cytotoxic function in fish. This review summarizes the morphological and functional evidence for cytotoxic cells within bony fish and discusses future directions for examining cytotoxicity through genomics and transgenics.