Effect of dapagliflozin on collectins and complement activation in plasma from patients with type 2 diabetes and albuminuria: Data from the DapKid cohort.

BACKGROUND: Sodium-glucose cotransporter 2 (SGLT- 2) inhibitors exert cardiovascular and kidney-protective effects in people with diabetes. Attenuation of inflammation could be important for systemic protection. The lectin pathway of complement system activation is linked to diabetic nephropathy. We hypothesized that SGLT-2 inhibitors lower the circulating level of pattern-recognition molecules of the lectin cascade and attenuate systemic complement activation. METHODS: Analysis of paired plasma samples from the DapKid crossover intervention study where patients with type 2 diabetes mellitus (T2DM) and albuminuria were treated with dapagliflozin and placebo for 12 weeks (10 mg/day, n=36). ELISA was used to determine concentrations of collectin kidney 1 (CL-K1), collectin liver 1 (CL-L1), mannose-binding lectin (MBL), MBL-associated serine protease 2 (MASP-2), the anaphylatoxin complement factor 3a (C3a), the stable C3 split product C3dg and the membrane attack complex (sC5b-9). RESULTS: As published before, dapagliflozin treatment lowered Hba1C from 74 (14.9) mmol/mol to 66 (13.9) mmol/mol (p<0.0001), and the urine albumin/creatinine ratio from 167.8 mg/g to 122.5 mg/g (p<0.0001). Plasma concentrations of CL-K1, CL-L1, MBL, and MASP-2 did not change significantly after dapagliflozin treatment (P>0.05) compared to placebo treatment. The plasma levels of C3a (P<0.05) and C3dg (P<0.01) increased slightly but significantly, 0.6 [0.2] units/mL and 76 [52] units/mL respectively, after dapagliflozin treatment. The C9-associated neoepitope in C5b-9 did not change in plasma concentration by dapagliflozin (P>0.05). CONCLUSION: In patients with type 2 diabetes and albuminuria, SGLT-2 inhibition resulted in modest C3 activation in plasma, likely not driven by primary changes in circulating collectins and not resulting in changes in membrane attack complex. Based on systemic analyses, organ-specific local protective effects of gliflozins against complement activation cannot be excluded.

Potency measurements of the complement system facilitated by antibodies targeting the zymogen form of complement factor D (Adipsin).

The serine protease complement factor D is fundamental in the activation of the complement system. In addition, it was the first adipokine described (named Adipsin) and shown to improve beta cell function in diabetes. As part of an amplification loop of complement activation, factor D is a rate-limiting enzyme, and its accessibility contributes to the potency of complement activation. The dogma has been that conversion of the zymogen form, profactor D, to mature factor D occurred during secretion by adipocytes by uncharacterized proteases. However, recent findings demonstrated that the serine protease MASP-3 of the lectin pathway of the complement system mediated this conversion, suggesting that pattern recognition of pathogen/danger-associated molecular patterns could be a prior requirement for all complement activation. To facilitate studies addressing this hypothesis, we have developed monoclonal antibodies specific for human profactor D without binding to mature factor D. We demonstrate their applications in accessing the conversion of profactor D into mature factor D and in measuring levels of profactor D.

A novel approach to evaluate ELISA antibody coverage of host cell proteins-combining ELISA-based immunocapture and mass spectrometry.

Monitoring host cell proteins (HCPs) is one of the most important analytical requirements in production of recombinant biopharmaceuticals to ensure product purity and patient safety. Enzyme-linked immunosorbent assay (ELISA) is the standard method for monitoring HCP clearance. It is important to validate that the critical reagent of an ELISA, the HCP antibody, covers a broad spectrum of the HCPs potentially present in the purified drug substance. Current coverage methods for assessing HCP antibody coverage are based on 2D-Western blot or immunoaffinity-purification combined with 2D gel electrophoresis and have several limitations. In the present study, we present a novel coverage method combining ELISA-based immunocapture with protein identification by liquid chromatography-tandem mass spectrometry (LC-MS/MS): ELISA-MS. ELISA-MS is used to accurately determine HCP coverage of an early process sample by three commercially available anti-Escherichia coli HCP antibodies, evading the limitations of current methods for coverage analysis, and taking advantage of the benefits of MS analysis. The results obtained comprise a list of individual HCPs covered by each HCP antibody. The novel method shows high sensitivity, high reproducibility, and enables tight control of nonspecific binding through inclusion of a species-specific isotype control antibody. We propose that ELISA-MS will be a valuable supplement to existing coverage methods or even a replacement. ELISA-MS will increase the possibility of selecting the best HCP ELISA, thus improving HCP surveillance and resulting in a final HCP profile with the lowest achievable risk. Overall, this will be beneficial to both the pharmaceutical industry and patient safety.

Novel Monoclonal Antibodies Against Native Human Collectin L1, Using the Heteromeric Complex CL-LK as Immunogen.

Collectin LK (CL-LK) is a recently described collectin complex, which upon binding to microbial glycoconjugates, activates the lectin pathway of the complement system, and thereby contributes to the removal of invading microorganisms. The complex consists of the two collectins; Collectin K1 (kidney 1 alias CL-11) and Collectin L1 (liver 1 alias CL-10). At present, most efforts have been made on the characterization of CL-K1, and little is known about the function of CL-L1 and its association with diseases. Deficiency of either of the two collectins is associated with the developmental syndrome 3MC, whereas increased plasma levels of CL-K1 are associated with disseminated intravascular coagulation. Using CL-LK purified from human plasma as an immunogen, we succeed in generating seven monoclonal antibodies (mAbs) with specificity for CL-L1. All seven mAbs recognize both native and recombinant CL-L1. In addition, four of the mAbs were successful in immunohistochemical detection of CL-L1 in human tissues. To our knowledge, these are the first mAbs specific for human native CL-L1 described in the literature, and we expect them to be of great importance in characterizing the function of CL-L1, as well as for the study of CL-L1's association with disease.

CL-L1 and CL-K1 Exhibit Widespread Tissue Distribution With High and Co-Localized Expression in Secretory Epithelia and Mucosa.

Collectin liver 1 (CL-L1, alias collectin 10) and collectin kidney 1 (CL-K1, alias collectin 11) are oligomeric pattern recognition molecules associated with the complement system, and mutations in either of their genes may lead to deficiency and developmental defects. The two collectins are reportedly localized and synthesized in the liver, kidneys, and adrenals, and can be found in the circulation as heteromeric complexes (CL-LK), which upon binding to microbial high mannose-like glycoconjugates activates the complement system via the lectin activation pathway. The tissue distribution of homo- vs. heteromeric CL-L1 and -K1 complexes, the mechanism of heteromeric complex formation and in which tissues this occurs, is hitherto incompletely described. We have by immunohistochemistry using monoclonal antibodies addressed the precise cellular localization of the two collectins in the main human tissues. We find that the two collectins have widespread and almost identical tissue distribution with a high expression in epithelial cells in endo-/exocrine secretory tissues and mucosa. There is also accordance between localization of mRNA transcripts and detection of proteins, showing that local synthesis likely is responsible for peripheral localization and eventual formation of the CL-LK complexes. The functional implications of the high expression in endo-/exocrine secretory tissue and mucosa is unknown but might be associated with the activity of MASP-3, which has a similar pattern of expression and is known to potentiate the activity of the alternative complement activation pathway.

Limonene and its ozone-initiated reaction products attenuate allergic lung inflammation in mice.

Inhalation of indoor air pollutants may cause airway irritation and inflammation and is suspected to worsen allergic reactions. Inflammation may be due to mucosal damage, upper (sensory) and lower (pulmonary) airway irritation due to activation of the trigeminal and vagal nerves, respectively, and to neurogenic inflammation. The terpene, d-limonene, is used as a fragrance in numerous consumer products. When limonene reacts with the pulmonary irritant ozone, a complex mixture of gas and particle phase products is formed, which causes sensory irritation. This study investigated whether limonene, ozone or the reaction mixture can exacerbate allergic lung inflammation and whether airway irritation is enhanced in allergic BALB/cJ mice. Naïve and allergic (ovalbumin sensitized) mice were exposed via inhalation for three consecutive days to clean air, ozone, limonene or an ozone-limonene reaction mixture. Sensory and pulmonary irritation was investigated in addition to ovalbumin-specific antibodies, inflammatory cells, total protein and surfactant protein D in bronchoalveolar lavage fluid and hemeoxygenase-1 and cytokines in lung tissue. Overall, airway allergy was not exacerbated by any of the exposures. In contrast, it was found that limonene and the ozone-limonene reaction mixture reduced allergic inflammation possibly due to antioxidant properties. Ozone induced sensory irritation in both naïve and allergic mice. However, allergic but not naïve mice were protected from pulmonary irritation induced by ozone. This study showed that irritation responses might be modulated by airway allergy. However, aggravation of allergic symptoms was observed by neither exposure to ozone nor exposure to ozone-initiated limonene reaction products. In contrast, anti-inflammatory properties of the tested limonene-containing pollutants might attenuate airway allergy.

The collectins CL-L1, CL-K1 and CL-P1, and their roles in complement and innate immunity.

Both the complement system and collectins play important roles in our innate immune system. The collectins, which are characterized by their inclusion of a collagen-like region and a calcium-dependent carbohydrate recognition domain, are pattern recognition molecules and include the well characterized proteins mannan-binding lectin (MBL) and the surfactant proteins SP-A/-D. Collectin liver 1 (CL-L1), collectin kidney 1 (CL-K1) and collectin placenta 1 (CL-P1) are the most recently discovered collectins. Although their function is still under investigation, accumulating information suggests that CL-L1, CL-K1 and CL-P1 play important roles in host defense by recognizing a variety of microorganisms and interacting with effector proteins, including complement components. The recent establishment of the existence of CL-K1 in the circulation in form of heteromeric complexes with CL-L1 (known as CL-LK) and its activation of the lectin pathway via MASPs, drew new attention in the complement biology, which was further strengthened by the observed interactions between CL-P1 and CRP-C1q-factor H or properdin. Deficiency of either CL-K1 or MASP-3 has been demonstrated in 3MC syndrome patients with developmental abnormalities, showing that lectin pathway components, regulation and/or activation are essential during the embryonic development; another feature that they most likely share CL-P1. Herein, we discuss the recent characteristics and roles of the collectins CL-L1, CL-K1 and CL-P1 in the complement system, in innate immunity and their possible association with disease development and pathogenesis.

Polarized Airway Epithelial Models for Immunological Co-Culture Studies.

Epithelial cells line all cavities and surfaces throughout the body and play a substantial role in maintaining tissue homeostasis. Asthma and other atopic diseases are increasing worldwide and allergic disorders are hypothesized to be a consequence of a combination of dysregulation of the epithelial response towards environmental antigens and genetic susceptibility, resulting in inflammation and T cell-derived immune responses. In vivo animal models have long been used to study immune homeostasis of the airways but are limited by species restriction and lack of exposure to a natural environment of both potential allergens and microflora. Limitations of these models prompt a need to develop new human cell-based in vitro models. A variety of co-culture systems for modelling the respiratory epithelium exist and are available to the scientific community. The models have become increasingly sophisticated and specific care needs to be taken with regard to cell types, culture medium and culture models, depending on the aim of the study. Although great strides have been made, there is still a need for further optimization, and optimally also for standardization, in order for in vitro co-culture models to become powerful tools in the discovery of key molecules dictating immunity and/or tolerance, and for understanding the complex interplay that takes place between mucosa, airway epithelium and resident or infiltrating immune cells. This review focuses on current knowledge and the advantages and limitations of the different cell types and culture methods used in co-culture models of the human airways.