Recombinant Human Tissue Non-Specific Alkaline Phosphatase Successfully Counteracts Lipopolysaccharide Induced Sepsis in Mice

Development of recombinant secondary antibody mimics (rSAMs) for immunoassays through genetic fusion of monomeric alkaline phosphatase with antibody binders

In conventional immunoassays, a secondary antibody is used to amplify the signal generated by the binding of the primary antibody to the target analyte. Due to concerns regarding animal use and cost-inefficiency of secondary antibody productions, there is a significant demand for the development of recombinant secondary antibody mimics (rSAMs). Here, we developed rSAMs using a signal-generating enzyme, monomeric alkaline phosphatase (mALP), and antibody-binders, including monomeric streptavidin (mSA2) and mouse IgG1- or rabbit IgG-binding nanobodies (MG1Nb or RNb). The mALP-MG1Nb, mALP-RNb, and mALP-mSA2 were genetically constructed and produced in large quantities using bacterial overexpression systems, which reduced manufacturing costs and time without the use of animals. Each rSAM exhibited high and selective binding to its respective primary antibody, generating linear band signals corresponding to the amounts of target analytes in western blots. The rSAMs also successfully generated sigmoidal signal curves that increased as the sample concentration increased. Moreover, they generated stronger signals than conventional ALP-conjugated secondary antibodies and SA, particularly in the medium to high sample concentration range, in both indirect and sandwich-type indirect ELISAs at the same sample concentration. The rSAMs we developed here may provide new insights to develop novel immunoassay-based analytical and diagnostic tools.

Babies, Bugs, and Barriers: Dietary Modulation of Intestinal Barrier Function in Early Life

The intestinal barrier is essential in early life to prevent infection, inflammation, and food allergies. It consists of microbiota, a mucus layer, an epithelial layer, and the immune system. Microbial metabolites, the mucus, antimicrobial peptides, and secretory immunoglobulin A (sIgA) protect the intestinal mucosa against infection. The complex interplay between these functionalities of the intestinal barrier is crucial in early life by supporting homeostasis, development of the intestinal immune system, and long-term gut health. Exclusive breastfeeding is highly recommended during the first 6 months. When breastfeeding is not possible, milk-based infant formulas are the only safe alternative. Breast milk contains many bioactive components that help to establish the intestinal microbiota and influence the development of the intestinal epithelium and the immune system. Importantly, breastfeeding lowers the risk for intestinal and respiratory tract infections. Here we review all aspects of intestinal barrier function and the nutritional components that impact its functionality in early life, such as micronutrients, bioactive milk proteins, milk lipids, and human milk oligosaccharides. These components are present in breast milk and can be added to milk-based infant formulas to support gut health and immunity. Expected final online publication date for the Annual Review of Nutrition, Volume 42 is August 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

TNAP as a therapeutic target for cardiovascular calcification: a discussion of its pleiotropic functions in the body

Cardiovascular calcification (CVC) is associated with increased morbidity and mortality. It develops in several diseases and locations, such as in the tunica intima in atherosclerosis plaques, in the tunica media in type 2 diabetes and chronic kidney disease, and in aortic valves. In spite of the wide occurrence of CVC and its detrimental effects on cardiovascular diseases (CVD), no treatment is yet available. Most of CVC involve mechanisms similar to those occurring during endochondral and/or intramembranous ossification. Logically, since tissue-nonspecific alkaline phosphatase (TNAP) is the key-enzyme responsible for skeletal/dental mineralization, it is a promising target to limit CVC. Tools have recently been developed to inhibit its activity and preclinical studies conducted in animal models of vascular calcification already provided promising results. Nevertheless, as its name indicates, TNAP is ubiquitous and recent data indicate that it dephosphorylates different substrates in vivo to participate in other important physiological functions besides mineralization. For instance, TNAP is involved in the metabolism of pyridoxal phosphate and the production of neurotransmitters. TNAP has also been described as an anti-inflammatory enzyme able to dephosphorylate adenosine nucleotides and lipopolysaccharide. A better understanding of the full spectrum of TNAP's functions is needed to better characterize the effects of TNAP inhibition in diseases associated with CVC. In this review, after a brief description of the different types of CVC, we describe the newly uncovered additional functions of TNAP and discuss the expected consequences of its systemic inhibition in vivo.

Novel drug discovery strategies for the treatment of decompensated cirrhosis

INTRODUCTION

Disease progression in cirrhosis leads to decompensation and acute-on-chronic liver failure (ACLF), which is characterized by organ failure and high mortality. Portal hypertension and cardiovascular dysfunction trigger the development of cirrhosis-related complications whilst tissue injury and cellular metabolic dysfunction lead to organ failure. System inflammation is the overarching mechanism mediating both the transition from compensation to decompensation as well as progression to ACLF. Treatment of precipitating events and intensive organ support is the only established therapeutic strategies. Liver transplantationrepresents the only curative therapy but contraindications and organ scarcity limit its availability to only a minority of patients with end-stage liver disease. Therefore, the discovery and development of novel interventions modifying the disease course and improving patients' outcome are of utmost importance.

AREAS COVERED

This review highlights and discusses therapeutic novelties in the field of end-stage liver disease.

EXPERT OPINION

Despite decades of research, there are still no established therapies to improve the devastating prognosis of patients with end-stage liver disease. The clinical heterogeneity and complex pathogenesis will put high demands on drug discovery. Combinatorial therapies tailored to the patients' individual pattern of pathomechanisms may be the most efficient way to modify disease course.

Biomolecules Orchestrating Cardiovascular Calcification

Vascular calcification, once considered a degenerative, end-stage, and inevitable condition, is now recognized as a complex process regulated in a manner similar to skeletal bone at the molecular and cellular levels. Since the initial discovery of bone morphogenetic protein in calcified human atherosclerotic lesions, decades of research have now led to the recognition that the regulatory mechanisms and the biomolecules that control cardiovascular calcification overlap with those controlling skeletal mineralization. In this review, we focus on key biomolecules driving the ectopic calcification in the circulation and their regulation by metabolic, hormonal, and inflammatory stimuli. Although calcium deposits in the vessel wall introduce rupture stress at their edges facing applied tensile stress, they simultaneously reduce rupture stress at the orthogonal edges, leaving the net risk of plaque rupture and consequent cardiac events depending on local material strength. A clinically important consequence of the shared mechanisms between the vascular and bone tissues is that therapeutic agents designed to inhibit vascular calcification may adversely affect skeletal mineralization and vice versa. Thus, it is essential to consider both systems when developing therapeutic strategies.

Tissue-Nonspecific Alkaline Phosphatase in Central Nervous System Health and Disease: A Focus on Brain Microvascular Endothelial Cells

Tissue-nonspecific alkaline phosphatase (TNAP) is an ectoenzyme bound to the plasma membranes of numerous cells via a glycosylphosphatidylinositol (GPI) moiety. TNAP's function is well-recognized from earlier studies establishing its important role in bone mineralization. TNAP is also highly expressed in cerebral microvessels; however, its function in brain cerebral microvessels is poorly understood. In recent years, few studies have begun to delineate a role for TNAP in brain microvascular endothelial cells (BMECs)-a key component of cerebral microvessels. This review summarizes important information on the role of BMEC TNAP, and its implication in health and disease. Furthermore, we discuss current models and tools that may assist researchers in elucidating the function of TNAP in BMECs.

Alkaline phosphatase in pulmonary inflammation-a translational study in ventilated critically ill patients and rats

Background

Alkaline phosphatase (AP), a dephosphorylating enzyme, is involved in various physiological processes and has been shown to have anti-inflammatory effects.

Aim

To determine the correlation between pulmonary AP activity and markers of inflammation in invasively ventilated critically ill patients with or without acute respiratory distress syndrome (ARDS), and to investigate the effect of administration of recombinant AP on pulmonary inflammation in a well-established lung injury model in rats

Methods

AP activity was determined and compared with levels of various inflammatory mediators in bronchoalveolar lavage fluid (BALF) samples obtained from critically ill patients within 2 days of start of invasive ventilation. The endpoints of this part of the study were the correlations between AP activity and markers of inflammation, i.e., interleukin (IL)-6 levels in BALF. In RccHan Wistar rats, lung injury was induced by intravenous administration of 10 mg/kg lipopolysaccharide, followed by ventilation with a high tidal volume for 4 h. Rats received either an intravenous bolus of 1500 IU/kg recombinant AP or normal saline 2 h after intravenous LPS administration, right before start of ventilation. Endpoints of this part of the study were pulmonary levels of markers of inflammation, including IL-6, and markers of endothelial and epithelial dysfunction.

Results

BALF was collected from 83 patients; 10 patients had mild ARDS, and 15 had moderate to severe ARDS. AP activity correlated well with levels of IL-6 (r = 0.70), as well as with levels of other inflammatory mediators. Pulmonary AP activity between patients with and without ARDS was comparable (0.33 [0.14–1.20] vs 0.55 [0.21–1.42] U/L; p = 0.37). Animals with acute lung injury had markedly elevated pulmonary AP activity compared to healthy controls (2.58 [2.18–3.59] vs 1.01 [0.80–1.46] U/L; p < 0.01). Intravenous administration of recombinant AP did neither affect pulmonary inflammation nor endothelial and epithelial dysfunction.

Conclusions

In ventilated critically ill patients, pulmonary AP activity correlates well with markers of pulmonary inflammation, such as IL-6 and IL-8. In animals with lung injury, pulmonary AP activity is elevated. Administration of recombinant AP does not alter pulmonary inflammation and endothelial or epithelial dysfunction in the acute phase of a murine lung injury model.

Recent advances in intestinal alkaline phosphatase, inflammation, and nutrition

In recent years, much new data on intestinal alkaline phosphatase (IAP) have been published, and major breakthroughs have been disclosed. The aim of the present review is to critically analyze the publications released over the last 5 years. These breakthroughs include, for example, the direct implication of IAP in intestinal tight junction integrity and barrier function maintenance; chronic intestinal challenge with low concentrations of Salmonella generating long-lasting depletion of IAP and increased susceptibility to inflammation; the suggestion that genetic mutations in the IAP gene in humans contribute to some forms of chronic inflammatory diseases and loss of functional IAP along the gut and in stools; stool IAP as an early biomarker of incipient diabetes in humans; and omega-3 fatty acids as direct inducers of IAP in intestinal tissue. Many recent papers have also explored the prophylactic and therapeutic potential of IAP and other alkaline phosphatase (AP) isoforms in various experimental settings and diseases. Remarkably, nearly all data confirm the potent anti-inflammatory properties of (I)AP and the negative consequences of its inhibition on health. A simplified model of the body AP system integrating the IAP compartment is provided. Finally, the list of nutrients and food components stimulating IAP has continued to grow, thus emphasizing nutrition as a potent lever for limiting inflammation.

Effects of intestinal alkaline phosphatase on intestinal barrier function in a cecal ligation and puncture (CLP)-induced mouse model for sepsis

BACKGROUND

Sepsis is a severe pathological condition associated with systemic inflammation, intestinal inflammation, and gastrointestinal barrier dysfunction. Intestinal alkaline phosphatase (IAP) has been demonstrated to detoxify lipopolysaccharide, an important mediator in the pathophysiology of sepsis. We investigated the effect of treatment with IAP on intestinal permeability, intestinal inflammation, and bacterial translocation.

METHODS

OF-1 mice were divided into 4 groups (n = 12/group), undergoing either a sham or cecal ligation and puncture (CLP) procedure to induce sepsis. Mice received IAP or a vehicle intraperitoneally 5 minutes prior to the onset of the CLP or sham procedure, which was repeated every 12 hours for two consecutive days. After two days, in vivo intestinal permeability, intestinal inflammation, and bacterial translocation were determined.

KEY RESULTS

CLP-induced sepsis resulted in significantly more weight loss, worse clinical disease scores, bacterial translocation, and elevated inflammatory cytokines. Intestinal permeability was increased up to 5-fold (P < .001). IAP activity was significantly increased in septic animals. Treatment with IAP had no effect on clinical outcomes but reduced the increased permeability of the small intestine by 50% (P = .005). This reduction in permeability was accompanied by a modified gene expression of claudin-1 (P = .025), claudin-14 (P = .035), and interleukin 12 (P = .015). A discriminant analysis showed that treatment with IAP is linked to modified mRNA levels of several tight junction proteins and cytokines.

CONCLUSIONS AND INFERENCES

Treatment with IAP diminished CLP-induced intestinal barrier disruption, associated with modified expression of several cytokines and claudins. Nevertheless, this effect did not translate into better clinical outcomes in our experimental setup.

Loss of tissue-nonspecific alkaline phosphatase (TNAP) enzyme activity in cerebral microvessels is coupled to persistent neuroinflammation and behavioral deficits in late sepsis

Sepsis is a host response to systemic inflammation and infection that may lead to multi-organ dysfunction and eventual death. While acute brain dysfunction is common among all sepsis patients, chronic neurological impairment is prevalent among sepsis survivors. The brain microvasculature has emerged as a major determinant of sepsis-associated brain dysfunction, yet the mechanisms that underlie its associated neuroimmune perturbations and behavioral deficits are not well understood. An emerging body of data suggests that inhibition of tissue-nonspecific alkaline phosphatase (TNAP) enzyme activity in cerebral microvessels may be associated with changes in endothelial cell barrier integrity. The objective of this study was to elucidate the connection between alterations in cerebrovascular TNAP enzyme activity and brain microvascular dysfunction in late sepsis. We hypothesized that the disruption of TNAP enzymatic activity in cerebral microvessels would be coupled to the sustained loss of brain microvascular integrity, elevated neuroinflammatory responses, and behavioral deficits. Male mice were subjected to cecal ligation and puncture (CLP), a model of experimental sepsis, and assessed up to seven days post-sepsis. All mice were observed daily for sickness behavior and underwent behavioral testing. Our results showed a significant decrease in brain microvascular TNAP enzyme activity in the somatosensory cortex and spinal cord of septic mice but not in the CA1 and CA3 hippocampal regions. Furthermore, we showed that loss of cerebrovascular TNAP enzyme activity was coupled to a loss of claudin-5 and increased perivascular IgG infiltration in the somatosensory cortex. Analyses of whole brain myeloid and T-lymphoid cell populations also revealed a persistent elevation of infiltrating leukocytes, which included both neutrophil and monocyte myeloid derived suppressor cells (MDSCs). Regional analyses of the somatosensory cortex, hippocampus, and spinal cord revealed significant astrogliosis and microgliosis in the cortex and spinal cord of septic mice that was accompanied by significant microgliosis in the CA1 and CA3 hippocampal regions. Assessment of behavioral deficits revealed no changes in learning and memory or evoked locomotion. However, the hot plate test uncovered a novel anti-nociceptive phenotype in our septic mice, and we speculate that this phenotype may be a consequence of sustained GFAP astrogliosis and loss of TNAP activity in the somatosensory cortex and spinal cord of septic mice. Taken together, these results demonstrate that the loss of TNAP enzyme activity in cerebral microvessels during late sepsis is coupled to sustained neuroimmune dysfunction which may underlie, in part, the chronic neurological impairments observed in sepsis survivors.

Recombinant Alkaline Phosphatase Prevents Acute on Chronic Liver Failure

The lipopolysaccharide (LPS)– toll-like receptor-4 (TLR4) pathway plays an important role in liver failure. Recombinant alkaline phosphatase (recAP) deactivates LPS. The aim of this study was to determine whether recAP prevents the progression of acute and acute-on-chronic liver failure (ACLF). Eight groups of rats were studied 4-weeks after sham surgery or bile duct ligation and were injected with saline or LPS to mimic ACLF. Acute liver failure was induced with Galactosamine-LPS and in both models animals were treated with recAP prior to LPS administration. In the ACLF model, the severity of liver dysfunction and brain edema was attenuated by recAP, associated with reduction in cytokines, chemokines, liver cell death, and brain water. The activity of LPS was reduced by recAP. The treatment was not effective in acute liver failure. Hepatic TLR4 expression was reduced by recAP in ACLF but not acute liver failure. Increased sensitivity to endotoxins in cirrhosis is associated with upregulation of hepatic TLR4, which explains susceptibility to development of ACLF whereas acute liver failure is likely due to direct hepatoxicity. RecAP prevents multiple organ injury by reducing receptor expression and is a potential novel treatment option for prevention of ACLF but not acute liver failure.

Raw cow's milk consumption and allergic diseases - The potential role of bioactive whey proteins

The prevalence of allergic diseases has increased significantly in Western countries in the last decades. This increase is often explained by the loss of rural living conditions and associated changes in diet and lifestyle. In line with this 'hygiene hypothesis', several epidemiological studies have shown that growing up on a farm lowers the risk of developing allergic diseases. The consumption of raw, unprocessed, cow's milk seems to be one of the factors contributing to this protective effect. Recent evidence indeed shows an inverse relation between raw cow's milk consumption and the development of asthma and allergies. However, the consumption of raw milk is not recommended due to the possible contamination with pathogens. Cow's milk used for commercial purposes is therefore processed, but this milk processing is shown to abolish the allergy-protective effects of raw milk. This emphasizes the importance of understanding the components and mechanisms underlying the allergy-protective capacity of raw cow's milk. Only then, ways to produce a safe and protective milk can be developed. Since mainly heat treatment is shown to abolish the allergy-protective effects of raw cow's milk, the heat-sensitive whey protein fraction of raw milk is an often-mentioned source of the protective components. In this review, several of these whey proteins, their potential contribution to the allergy-protective effects of raw cow's milk and the consequences of heat treatment will be discussed. A better understanding of these bioactive whey proteins might eventually contribute to the development of new nutritional approaches for allergy management.

Loss of CNFY toxin-induced inflammation drives Yersinia pseudotuberculosis into persistency

Gastrointestinal infections caused by enteric yersiniae can become persistent and complicated by relapsing enteritis and severe autoimmune disorders. To establish a persistent infection, the bacteria have to cope with hostile surroundings when they transmigrate through the intestinal epithelium and colonize underlying gut-associated lymphatic tissues. How the bacteria gain a foothold in the face of host immune responses is poorly understood. Here, we show that the CNFY toxin, which enhances translocation of the antiphagocytic Yop effectors, induces inflammatory responses. This results in extensive tissue destruction, alteration of the intestinal microbiota and bacterial clearance. Suppression of CNFY function, however, increases interferon-γ-mediated responses, comprising non-inflammatory antimicrobial activities and tolerogenesis. This process is accompanied by a preterm reprogramming of the pathogen's transcriptional response towards persistence, which gives the bacteria a fitness edge against host responses and facilitates establishment of a commensal-type life style.

Secretion of a recombinant protein without a signal peptide by the exocrine glands of transgenic rabbits

Transgenic rabbits carrying mammary gland specific gene constructs are extensively used for excreting recombinant proteins into the milk. Here, we report refined phenotyping of previously generated Venus transposon-carrying transgenic rabbits with particular emphasis on the secretion of the reporter protein by exocrine glands, such as mammary, salivary, tear and seminal glands. The Sleeping Beauty (SB) transposon transgenic construct contains the Venus fluorophore cDNA, but without a signal peptide for the secretory pathway, driven by the ubiquitous CAGGS (CAG) promoter. Despite the absence of a signal peptide, the fluorophore protein was readily detected in milk, tear, saliva and seminal fluids. The expression pattern was verified by Western blot analysis. Mammary gland epithelial cells of SB-CAG-Venus transgenic lactating does also showed Venus-specific expression by tissue histology and fluorescence microscopy. In summary, the SB-CAG-Venus transgenic rabbits secrete the recombinant protein by different glands. This finding has relevance not only for the understanding of the biological function of exocrine glands, but also for the design of constructs for expression of recombinant proteins in dairy animals.

[Effects of neutrophils alkaline phosphatase on functions of neutrophils in vitro]

目的

探讨中性粒细胞碱性磷酸酶（neutrophils alkaline phosphatase, NAP）对中性粒细胞迁移、活性氧（ROS）生成以及凋亡的影响。

方法

通过慢病毒感染人早幼粒细胞白血病细胞株HL-60获得NAP高表达细胞株，采用RT-PCR和Western blot技术分别检测感染后细胞NAP的基因转录及蛋白表达水平。HL-60细胞经1.5% DMSO体外诱导分化为类中性粒细胞后进行相关实验：分别利用Transwell迁移实验和流式细胞术检测高表达NAP中性粒细胞的迁移及ROS生成能力；流式细胞术检测细胞凋亡；Western blot法检测高表达NAP中性粒细胞中凋亡相关蛋白Bax、caspase-3和caspase-9的表达情况。

结果

经慢病毒感染的HL-60细胞通过嘌呤霉素筛选后80％以上细胞可见绿色荧光，且NAP在基因及蛋白水平表达均明显升高。HL-60细胞经1.5% DMSO体外诱导分化5 d后，细胞体积变小、表面出现许多突起，核质比例降低，核仁消失，核染色质由密集趋向疏松，细胞核扭曲折叠呈杆状或分叶，CD11b⁺细胞百分比明显升高。Transwell迁移实验结果显示，高表达NAP的中性粒细胞迁移细胞数多于阴性对照组[（15.30±3.65）×10³对（8.00±0.78）×10³，P<0.001]。流式细胞术检测结果表明，高表达NAP的中性粒细胞胞内ROS的平均荧光强度高于阴性对照组（355.70±20.10对103.22±4.71，P<0.001）；与阴性对照组比较，高表达NAP中性粒细胞胞凋亡率及凋亡相关蛋白Bax、active-caspase-3以及active-caspase-9的表达水平明显上调。

结论

NAP具有促进类中性粒细胞迁移及ROS生成、加速细胞凋亡的生物学作用。