Electrochemical nano-biosensor based on electrospun indium zinc oxide nanofibers for the determination of complement component 3 protein

Age-related macular degeneration (AMD) is a progressive chronic neurodegenerative retinal disease leading to vision loss, irreversible blindness, and visual impairment in older adults worldwide. Complement component 3 (C3) protein has been identified as the most predominant biomarker towards early diagnosis of AMD; therefore, there is an utmost requirement for non-invasive detection of C3 protein in the tear fluids of AMD patients. Considering this, we report an insightful electrochemical sensor capable of detecting clinically relevant concentrations ranging from 10 fg/mL to 1 μg/mL using electrospun indium-doped zinc oxide (InZnO) nanofibers as the transducing layer. The InZnO nanofibers have facilitated high anti-C3 antibody loading of 3.42 × 10^-9 mol/cm² and enhanced the overall charge transport mechanism at the sensor interface. The biofunctionalization process of the biosensor was investigated thoroughly using X-ray photoelectron spectroscopy (XPS) as well as different electrochemical techniques. The target C3 proteins were captured on the fabricated biosensor surface and determined through changes in charge transfer resistance (R_CT) while executing electrochemical impedance spectroscopy (EIS) and peak current (I_p) in the case of cyclic voltammetry (CV) and differential pulse voltammetry (DPV), respectively. The InZnO nanofiber-based nano-biosensor demonstrated a very low limit of detections (LODs) of 5.214 fg/mL and 0.241 fg/mL with an excellent sensitivity of 4.6709 (ΔR/R) (g/mL)^-1 cm^-2 and 54.4939 (ΔI_p/I_p)% (g/mL)^-1 cm^-2 for EIS and DPV techniques, respectively. By virtue of high antibody loading, ultrasensitive and ultra-selective capability, the indium-doped ZnO nanofibers show huge potential to be used as a high-performance diagnostic platform for AMD diagnosis.

Identification of intermolecular bonds between human factor B and Cobra Venom Factor important for C3 convertase stability

Cobra venom factor (CVF) is the complement-activating protein in cobra venom. CVF is a structural and functional analog of complement component C3. CVF, like C3b, forms a convertase with factor B. This bimolecular complex CVF, Bb is an enzyme that cleaves C3 and C5. However, CVF, Bb exhibits significantly different functional properties from C3b,Bb. Whereas both, CVF, Bb and C3b, Bb exhibit spontaneous decay-dissociation into the respective subunits, thereby eliminating the enzymatic activity, the CVF, Bb convertase is physico-chemically far more stable, decaying with a half-life that is more than two orders of magnitude slower than that of C3b,Bb. In addition, CVF, Bb is completely resistant to inactivation by Factors H and I. These two properties of CVF, Bb allow continuous activation of C3 and C5, and complement depletion in serum. In order to understand the structural basis for the physico-chemical stability of CVF,Bb, we have created recombinant hybrid proteins of CVF and human C3, based on structural differences between CVF and human C3b in the C-terminal C345C domain. Here we describe three human C3/CVF hybrid proteins which differ in only one, two, or five amino acid residues from earlier described hybrid proteins. In all three cases, the hybrid proteins containing CVF residues form more stable convertases, and exhibit stronger complement-depletion activity than hybrid proteins with human C3 residues. Three bonds between CVF residues and Factor Bb residues could be identified by crystallographic modeling that contribute to the greater stability of the convertases.

Gender differences on oxidative stress markers and complement component C3 plasma values after an oral unsaturated fat load test

OBJECTIVE

Post-prandial lipaemia (PL), oxidative stress (OS), and complement component C3 (C3) values are related to the atherosclerosis process. The post-prandial response of C3 after an oral fat load test (OFLT) using unsaturated fat is poorly addressed. The aim of this study was to analyze and compare the post-prandial response of OS markers and C3 values in men and women after an OFLT using unsaturated fat.

METHODS

The study included a total of 22 healthy subjects with normal lipids and normal blood glucose (11 men and 11 pre-menopausal women). An oral unsaturated fat load test (OFLT: 50g fat per m² body surface) was performed using a commercial liquid preparation of long chain triglycerides (Supracal®). OS markers and C3 were measured using standardized methods at fasting state and every 2h up to 8h after the OFLT.

RESULTS

Men showed statistically significant higher C3, oxidized glutathione (GSSG), and oxidized-reduced glutathione (GSSG/GSH) ratio values at fasting state compared to that obtained in women. In addition, post-prandial C3 values and GSSG/GSH ratios were significantly higher in men compared to women. The GSSG value and GSSG/GSH ratio significantly decreased in men after the OFLT compared to fasting values. In contrast, the post-prandial OS markers decrease observed in women was not statistically significant.

CONCLUSIONS

In fasting state, men showed higher statistically significant C3 values and OS markers than women. The post-prandial OS markers (GSSG and GSSG/GSH ratio) significantly decrease after the OFLT with unsaturated fat in men compared to women.

Molecular cloning of complement component C3 gene from pearl mussel, Hyriopsis cumingii and analysis of the gene expression in response to tissue transplantation

Complement component C3 is well recognized as the central mediator of complement system, whose activation is responsible for the immune surveillance and elimination of non-self-antigens. In this study, C3 gene (HcC3) from a pearl making mussel, Hyriopsis cumingii, was successfully identified. The putative HcC3 possessed the canonical domains and highly conserved functional residues of C3 family members. In phylogenetic analysis, HcC3 was also clustered into C3 subfamily and separated from α2 macroglobulin clade. HcC3 gene was constitutively expressed in a wide range of tissues of pearl mussels, among which the immune-related tissues like hemocytes got highest expression. After allograft surgery of mantle tissues for aquaculture pearl production, the gene expression of HcC3 exhibited a rapid upregulation on day 1, dropped back on day 3, peaked the value on day 7, and restored to the level similar to control samples on day 14 after mantle allograft. The biphasic expression within the two weeks post the surgery suggests the important roles for HcC3 in alloimmune responses and an intricate complement activation mechanism in mollusks during tissue allograft.

Expression, purification, and characterization of a human complement component C3 analog that lacks the C-terminal C345c domain

The complement system consists of a series of soluble and cell-surface proteins that serve numerous roles in innate immunity, development, and homeostasis. Despite its many functions, the central event in the complement system is the proteolytic activation of the 185 kDa complement component 3 (C3) into its opsonin and anaphylatoxin fragments known as C3b (175 kDa) and C3a (10 kDa), respectively. The C3 protein is comprised of thirteen separate structural domains, several of which undergo extensive structural rearrangement upon activation to C3b. In addition to this, the C-terminal C345c domain found in C3, C3b, and the terminal degradation product, C3c (135 kDa), appears to adopt multiple conformations relative to the remainder of the molecule. To facilitate various structure/function studies, we designed two C3 analogs that could be activated to a C345c-less, C3c-like state following treatment with Tobacco Etch Virus (TEV) protease. We generated stably transfected Chinese Hamster Ovary (CHO) cell lines that secrete approximately 1.5 mg of the highest-expressing C3 analog per liter of conditioned culture medium. We purified this C3 analog by sequential immobilized metal ion affinity and size exclusion chromatographies, activated the protein by digestion with TEV protease, and purified the resulting C3c analog by a final size exclusion chromatography. The conformations and activities of our C3 and C3c analogs were assessed by measuring their binding profiles to known C3/b/c ligands by surface plasmon resonance. Together, this work demonstrates the feasibility of producing a C3 analog that can be site-specifically activated by an exogenous proteolytic enzyme.

Molecular characterization and expression analysis of complement component C3 in southern catfish (Silurus meridionalis) and a whole mount in situ hybridization study on its ontogeny

The complement system plays an important role in protecting fish against attack by pathogens early in life. Complement component C3 is a central component in the complement system. The present work aimed to clone the full length C3 cDNA sequence of southern catfish (Silurus meridionalis), detect the tissue expression patterns of C3, investigate the ontogeny of C3 in embryo and larva, and assess the expression of C3 in response to pathogen infection. The full length C3 cDNA sequence of 5157 bp with an open reading frame (ORF) of 4938 bp was cloned from southern catfish. The deduced amino acid sequence showed similarity with other teleost fish. The mRNA expression of C3 was detected in liver, spleen, stomach, intestine, and head kidney with RT-PCR and in situ hybridization. Whole mount in situ hybridization results revealed that C3 was first expressed in the yolk syncytial layer at 34 h post fertilization (hpf), followed by the liver at 36 h post hatching (hph). When challenged with Aeromonas hydrophila, the transcripts of C3 showed a significant up-regulation in liver and spleen at 24 h. The results suggested that complement C3 played a key role in defense against invading pathogens in the early development stages of southern catfish. Therefore, these results provide important information to understand the functions of C3 during fish early development in Siluriformes.

Does replacing sedentary behaviour with light or moderate to vigorous physical activity modulate inflammatory status in adults?

BACKGROUND

Sedentary behaviour, obesity and insulin resistance are associated with pro-inflammatory status. Limited data on whether physical activity modulates inflammatory status and counteracts obesity and insulin resistance associated low-grade inflammation exist. Our objective was to investigate associations between objectively measured physical activity and inflammatory status, and specifically whether substituting daily sedentary behaviour with light activity or moderate to vigorous physical activity (MVPA), is associated with beneficial alterations to the inflammatory profile among middle-aged adults and those at increased cardiometabolic risk (obese and insulin resistant subjects).

METHODS

Data are from a sub-sample of the Mitchelstown cohort; a population-based cross-sectional sample of 2047 Irish adults. Physical activity intensity and duration were measured in 396 participants for 7-consecutive days using the GENEActiv accelerometer. Isotemporal regression analysis examined the associations between replacing 30 min per day of sedentary behaviour with equal amounts of light activity and MVPA on inflammatory factors (serum acute-phase reactants, adipocytokines, pro-inflammatory cytokines and white blood cells (WBC)).

RESULTS

Reallocating 30 min of sedentary time with MVPA was associated with a more favourable inflammatory profile characterized by higher adiponectin and lower complement component C3 (C3), leptin, interleukin 6 (IL-6) and WBC concentrations (P < 0.05). No significant effects were noted with substitution of sedentary time with light activity. Among the obese subjects replacing sedentary behaviour with an equivalent amount of MVPA was associated with lower WBC counts (P < 0.05); no associations were detected among the insulin resistant (HOMA-IR >75th percentile) subjects. Among the non-obese and non-insulin resistant subjects substituting 30 min of sedentary behaviour with MVPA was associated with decreased C3, IL-6 and WBC concentrations.

CONCLUSIONS

Replacing sedentary behaviour with MVPA modulates pro-inflammatory status. These findings, which highlight the need for the developing randomized trials aimed at lowering cardiometabolic risk, warrant further investigation.

HIV induces expression of complement component C3 in astrocytes by NF-κB-dependent activation of interleukin-6 synthesis

BACKGROUND

Abnormal activation of the complement system contributes to some central nervous system diseases but the role of complement in HIV-associated neurocognitive disorder (HAND) is unclear.

METHODS

We used real-time PCR and immunohistochemistry to detect complement expression in postmortem brain tissue from HAND patients and controls. To further investigate the basis for viral induction of gene expression in the brain, we studied the effect of HIV on C3 expression by astrocytes, innate immune effector cells, and targets of HIV. Human fetal astrocytes (HFA) were infected with HIV in culture and cellular pathways and factors involved in signaling to C3 expression were elucidated using pharmacological pathway inhibitors, antisense RNA, promoter mutational analysis, and fluorescence microscopy.

RESULTS

We found significantly increased expression of complement components including C3 in brain tissues from patients with HAND and C3 was identified by immunocytochemistry in astrocytes and neurons. Exposure of HFA to HIV in culture-induced C3 promoter activity, mRNA expression, and protein production. Use of pharmacological inhibitors indicated that induction of C3 expression by HIV requires NF-κB and protein kinase signaling. The relevance of NF-κB regulation to C3 induction was confirmed through detection of NF-κB translocation into nuclei and inhibition through overexpression of the physiological NF-κB inhibitor, I-κBα. C3 promoter mutation analysis revealed that the NF-κB and SP binding sites are dispensable for the induction by HIV, while the proximal IL-1β/IL-6 responsive element is essential. HIV-treated HFA secreted IL-6, exogenous IL-6 activated the C3 promoter, and anti-IL-6 antibodies blocked HIV activation of the C3 promoter. The activation of IL-6 transcription by HIV was dependent upon an NF-κB element within the IL-6 promoter.

CONCLUSIONS

These results suggest that HIV activates C3 expression in primary astrocytes indirectly, through NF-κB-dependent induction of IL-6, which in turn activates the C3 promoter. HIV induction of C3 and IL-6 in astrocytes may contribute to HIV-mediated inflammation in the brain and cognitive dysfunction.

Dietary β-glucan (MacroGard®) enhances survival of first feeding turbot (Scophthalmus maximus) larvae by altering immunity, metabolism and microbiota

Reflecting the natural biology of mass spawning fish aquaculture production of fish larvae is often hampered by high and unpredictable mortality rates. The present study aimed to enhance larval performance and immunity via the oral administration of an immunomodulator, β-glucan (MacroGard(®)) in turbot (Scophthalmus maximus). Rotifers (Brachionus plicatilis) were incubated with or without yeast β-1,3/1,6-glucan in form of MacroGard(®) at a concentration of 0.5 g/L. Rotifers were fed to first feeding turbot larvae once a day. From day 13 dph onwards all tanks were additionally fed untreated Artemia sp. nauplii (1 nauplius ml/L). Daily mortality was monitored and larvae were sampled at 11 and 24 dph for expression of 30 genes, microbiota analysis, trypsin activity and size measurements. Along with the feeding of β-glucan daily mortality was significantly reduced by ca. 15% and an alteration of the larval microbiota was observed. At 11 dph gene expression of trypsin and chymotrypsin was elevated in the MacroGard(®) fed fish, which resulted in heightened tryptic enzyme activity. No effect on genes encoding antioxidative proteins was observed, whilst the immune response was clearly modulated by β-glucan. At 11 dph complement component c3 was elevated whilst cytokines, antimicrobial peptides, toll like receptor 3 and heat shock protein 70 were not affected. At the later time point (24 dph) an anti-inflammatory effect in form of a down-regulation of hsp 70, tnf-α and il-1β was observed. We conclude that the administration of MacroGard(®) induced an immunomodulatory response and could be used as an effective measure to increase survival in rearing of turbot.

Complement component 3 is necessary to preserve myocardium and myocardial function in chronic myocardial infarction

Activation of the complement cascade (CC) with myocardial infarction (MI) acutely initiates immune cell infiltration, membrane attack complex formation on injured myocytes, and exacerbates myocardial injury. Recent studies implicate the CC in mobilization of stem/progenitor cells and tissue regeneration. Its role in chronic MI is unknown. Here, we consider complement component C3, in the chronic response to MI. C3 knockout (KO) mice were studied after permanent coronary artery ligation. C3 deficiency exacerbated myocardial dysfunction 28 days after MI compared to WT with further impaired systolic function and LV dilation despite similar infarct size 24 hours post-MI. Morphometric analysis 28 days post-MI showed C3 KO mice had more scar tissue with less viable myocardium within the infarct zone which correlated with decreased c-kit(pos) cardiac stem/progenitor cells (CPSC), decreased proliferating Ki67(pos) CSPCs and decreased formation of new BrdU(pos) /α-sarcomeric actin(pos) myocytes, and increased apoptosis compared to WT. Decreased CSPCs and increased apoptosis were evident 7 days post-MI in C3 KO hearts. The inflammatory response with MI was attenuated in the C3 KO and was accompanied by attenuated hematopoietic, pluripotent, and cardiac stem/progenitor cell mobilization into the peripheral blood 72 hours post-MI. These results are the first to demonstrate that CC, through C3, contributes to myocardial preservation and regeneration in response to chronic MI. Responses in the C3 KO infer that C3 activation in response to MI expands the resident CSPC population, increases new myocyte formation, increases and preserves myocardium, inflammatory response, and bone marrow stem/progenitor cell mobilization to preserve myocardial function.