Carbonic Anhydrase III Research Articles

Synthesis and Biological Evaluation of Carbonic Anhydrase III and IX Inhibitors using Gas Chromatography with Modified pH Sensitive Pellets

Fifteen compounds were synthesized and tested as potential carbonic anhydrase III (CAIII) and carbonic anhydrase IX (CAIX) inhibitors, six of which are novel. Amides (a1-4), hydroxamic acids (b1-2), and imines (c1-9) derivatives were evaluated for their inhibitory activity against CAII and CAIX using gas chromatography with modified pH-sensitive pellets. The derivatives showed inhibition percentages between 12-56% for CAIII and 44-59% for CAIX, compared to 49% and 63% for captopril (the positive control), respectively. Imines showed the best inhibition of CAIII, while all derivatives showed comparable activity against CAIX. It is hypothesized that the nitrogen atom in imine, amide, or hydroxamic acid moieties in the vicinity of an ionizable group is in coordination with the zinc ion in the active site. Furthermore, the candidates were tested for their antimicrobial and antifungal activity. Generally, they showed low to zero activity against some gram-positive and negative bacteria. This supports the theory of their ability to bind to human carbonic anhydrase but not to bacterial one. These compounds could serve as useful scaffolds to develop more potent and selective carbonic anhydrase inhibitors as anti-obesity and anticancer candidates.

Carbonic Anhydrase III Has Potential as a Biomarker for Experimental Colitis and Functions as an Immune Regulator by Inhibiting Inflammatory Cytokine Secretion.

Simple SummaryThe mechanism underlying the onset of ulcerative colitis (UC) has not yet been elucidated in detail. Unknown components in colorectal tissue may be important risk factors to elucidate the cause of UC; however, they have not been highlighted as targets. To identify key factors, rats with dextran sulfate sodium-induced experimental colitis were used. The level of carbonic anhydrase III was significantly decreased in both the serum and colon tissues of these UC rats. Upon stimulation of peritoneal macrophages (MΦ) with lipopolysaccharide, the intracellular concentration of carbonic anhydrase III significantly decreased, while the secretion of pro-inflammatory cytokines from MΦ treated with an anti-carbonic anhydrase III antibody was negatively regulated. In conclusion, carbonic anhydrase III may be a novel regulator of experimental colitis in rats.Ulcerative colitis (UC) is characterized by chronic inflammation of the large intestine, repeated remissions, and symptom relapses. Although unknown components in colonic regions are deeply involved in the pathogenesis of UC, the causes of UC development and aggravation have not yet been elucidated in detail. To identify key factors, we investigated the changes in protein components in the large intestine of rats with dextran sulfate sodium-induced experimental colitis (UCR). The components that differed in their concentration between normal rats (WT) and UCR were carefully investigated by electrophoretic separation and mass spectrometry. Based on these results, seven proteins with different expression levels between the WT and UCR were observed. Among them, we focused on carbonic anhydrase III (CA-III) in the pathogenesis of UC. CA-III concentrations in the colon tissue and serum were quantitatively measured using an enzyme-linked immunosorbent assay (ELISA) and real-time PCR, and the levels significantly decreased in both the colon tissue and serum of UCR with the aggravation of experimental UC. In an in vitro assay, CA-III function in peritoneal macrophages (MΦ) from rats was investigated. Upon stimulation of MΦ with lipopolysaccharide (LPS), the CA-III concentration significantly decreased in the cytoplasm of these cells. MΦ treated with an anti-CAIII antibody followed by stimulation with LPS actively secreted inflammatory cytokines, particularly interleukin-6 and tumor necrosis factor-α. Therefore, CA-III in MΦ appears to be an immune regulator that suppresses the secretion of inflammatory cytokines.

The role of carbonic anhydrase III and autophagy in type 2 diabetes with cardio-cerebrovascular disease

Type 2 diabetes mellitus (T2DM) is one of the most common chronic diseases among the elderly people. The T2DM increases the risk of cardio-cerebrovascular disease (CCD), and the main pathological change of the CCD is atherosclerosis (AS). Meanwhile, the carbonic anhydrases (CAs) are involved in the formation and progression of plaques in AS. However, the exact physiological mechanism of carbonic anhydrase III (CAIII) has not been clear yet, and there are also no correlation study between CAIII protein and T2DM with CCD. The 8-week old diabetic mice (db/db−/− mice) and wild-type mice (wt mice) were feed by a normal diet till 32 weeks, and detected the carotid artery vascular opening angle using the method of biomechanics; The changes of cerebral cortex and myocardium were watched by the ultrastructure, and the autophagy were observed by electron microscope; The tissue structure, inflammation and cell injury were observed by Hematoxylin and eosin (HE) staining; The apoptosis of cells were observed by TUNEL staining; The protein levels of CAIII, IL-17, p53 were detected by immunohistochemical and Western Blot, and the Beclin-1, LC3, NF-κB were detected by Western Blot. All statistical analysis is performed using PRISM software. Compared with wt mice, db/db−/− mice’ carotid artery open angle increased significantly. Electron microscope results indicated that autophagy in db/db−/− mice cerebral cortex and heart tissue decreased and intracellular organelle ultrastructure were damaged. HE staining indicated that, db/db−/− mice’ cerebral cortex and heart tissue stained lighter, inflammatory cells infiltration, cell edema were obvious, myocardial fibers were disorder, and myocardial cells showed different degrees of degeneration. Compared with wt mice, TUNEL staining showed that there was obviously increase in db/db−/− mice cortex and heart tissue cell apoptosis. The results of immunohistochemistry and Western Blot indicated that CAIII, Beclin-1 and LC3II/I expression levels conspicuously decreased in cortex and heart tissue of db/db−/− mice, and the expression level of IL-17, NF-κB and p53 obviously increased. The carotid artery’ vascular stiffness was increased and which was probably related with formation of AS in diabetic mice. And the autophagy participated in the occurrence and development of diabetic CCD. CAIII protein might somehow be involved in the regulation of autophagy probably through affecting cell apoptosis and inflammation, but the underlying mechanism remains to be further studied.

Aldolase A and carbonic anhydrase III, two new candidate biomarkers versus acknowledged parameters in the context of crushing syndrome

Introduction. Crushing syndrome can affect all structures of a limb and can cause unique or complex injuries. The clinical picture of the injuries is nonspecific and extremely varied, and is not characteristic of the mechanism that generated it. The aim of our study was to correlate the changes of ALD A (aldolase A) and CAIII (carbonic anhydrase III) in the appearance and evolution of the crushing syndrome. Material and methods. The present study included 22 patients with crushing syndrome. The control group consisted of 20 healthy subjects. IL-6 (interleukin-6), CK (creatine kinase), ALD A and CAIII blood levels were determined simultaneously from all the participants to the study. Statistical analysis was performed using IBM SPSS Statistics 25 and Microsoft Office Excel / Word 2013. Results. Our results showed significantly increased levels of ALD A, CAIII, IL-6 and CK in patients with crushing syndrome. However, no statistically significant correlations could be found between the studied biomarkers. Discussions. So far, in the medical literature, very few studies focused on the correlation between the occurrence of crushing syndrome and changes in ALD A and CA III levels. Conclusions. Our study showed that ALD A and CAIII may become important biomarkers for the rapid diagnosis of crushing syndrome in the future.

Carbonic Anhydrase III Attenuates Hypoxia-Induced Apoptosis and Activates PI3K/Akt/mTOR Pathway in H9c2 Cardiomyocyte Cell Line.

Myocardial ischemia can cause insufficient oxygen and functional damage to myocardial cells. Carbonic anhydrase III (CAIII) has been found to be closely related to the abnormality of cardiomyocytes. To investigate the role of CAIII in the apoptosis of myocytes under hypoxic conditions and facilitate the strategy for treating hypoxia-induced damage, in vitro experiments in H9c2 were employed. The protein expression of CAIII in H9c2 cells after hypoxia or normoxia treatment was determined by western blotting and immunohistochemistry. MTT assay was employed for cells viability measurement and LDH release was monitored. The apoptotic cells were observed using immunofluorescence assay, flow cytometric analysis, and TUNEL assay. CAIII-overexpression or -knockdown cells were constructed to determine the role of CAIII in regulating apoptosis-related proteins caspase-3, Bax, Bcl-2, and anti-apoptosis pathway PI3K/Akt/mTOR. The mRNA levels of CAIII and genes related to CAIII synthesis including REN, IGHM, APOBEC 3F, and SKOR2 were significantly upregulated in hypoxia fetal sheep. The expression of CAIII protein and content of apoptotic H9c2 cells were increased at 1, 3, 6, and 12h after hypoxia treatment. Overexpression of CAIII significantly upregulated Bcl2 level and downregulated Bax and caspase-3 cleavagelevels, while its knockdown led to the contrary results. Overexpressed CAIII promoted the HIF-1α level and activated the PI3K/Akt/mTOR pathway, thereby exerting an inhibitory effect on hypoxia-induced apoptosis. In conclusion, our findings revealed that CAIII could protect cell from hypoxia-apoptosis of H9c2 cells, in which, activated PI3K/Akt/mTOR signaling pathway may be involved.

Inhibitory Binding of Angiotensin Converting Enzyme Inhibitors with Carbonic Anhydrase III

Both angiotensin converting enzyme (ACE) and carbonic anhydrase III (CAIII) are zinc-containing enzymes. Interestingly, blocking of the both enzymes is attributed with clinically significant outcomes against hyperlipidemia and obesity. An optimized in-vitro screening approach based on HPLC–size exclusion chromatography was adopted to study the angiotensin converting enzyme inhibitors (ACEIs) affinity against CAIII enzyme. Series of concentrations of the enzyme were injected in the column with a mobile phase containing one of ACEIs in each time. The affinity of the ACEIs toward CAIII was characterized by vacancy (negative) peak whose intensity representing the fraction of the drug bound with CAIII. To explore whether the binding is within the binding site or just a promiscuous binding, exact procedure was repeated with apo-protein part of CAIII. Furthermore, an esterase activity of CAIII was performed to determine if the binding with ACEIs is excitatory or inhibitory. It has been found that ACEIs have real in-vitro inhibitory effects against CAIII at a micro-molar level. The chromatographic study revealed that the ionized carboxylate groups are essential for binding with Zn+2 ion in the enzyme active site. Among the four tested ACEIs, captopril, ramipril, enalapril, and lisinopril, captopril was found to be the most potent inhibitor with Ki = 12.1 μM, while lisinopril is the least potent one with Ki = 25.3 μM. This finding might open the door for further investigation to optimize ACEIs as lead compounds for the discovery and development of selective and potent CAIII inhibitors.

Carbonic anhydrase III is a new target of HIF1α in prostate cancer model.

Carbonic Anhydrase III (CAIII) belongs to a member of the alpha Carbonic Anhydrase (CA) family. Although some CA members are strongly up-regulated by HIF1-α, it is not known about the transcriptional regulation of CAIII in prostate cancer cells, PCa. Therefore, we aimed to identify regulatory regions important for the regulation of CAIII gene under hypoxic conditions in human prostate cancer cells (PC3). The present study, for the first time, demonstrated that the chemically mimicked hypoxic condition led to the induced CAIII mRNA and protein expression in prostate cancer cells. Transcriptional regulation of CAIII was investigated by transient transfection assay that indicates that the most active promoter activity was in the region of P2 -699/+86. Hypoxic condition also upregulates the basal activity of for P1;-941/+86 and P2;-699/+86 constructs containing putative Hypoxia Response Element (HRE) region located in -268/-252. EMSA analysis of HRE located in -268/-252 bases, showed one DNA-protein binding complexes. Competition assays indicated this complex is resulted from HIF1α interactions. In addition, site-directed mutagenesis of potential HIF1α binding sites diminished a DNA-protein complex. These findings suggest that CAIII is a hypoxia-regulated gene and valuable for targeting of prostate cancer tumors in hypoxic condition.

Synthesis and evaluation of 2,4,5-trisubstitutedthiazoles as carbonic anhydrase-III inhibitors

A series of 17 compounds (12–16 b) with 2,4,5-trisubstitutedthiazole scaffold having 5-aryl group, 4-carboxylic acid/ester moiety, and 2-amino/amido/ureido functional groups were synthesised, characterised, and evaluated for their carbonic anhydrase (CA)-III inhibitory activities using the size exclusion Hummel–Dreyer method (HDM) of chromatography. Compound 12a with a free amino group at the 2-position, carboxylic acid moiety at the 4-position, and a phenyl ring at the 5-position of the scaffold was found to be the most potent CA-III inhibitor (Ki = 0.5 μM). The presence of a carboxylic acid group at the 4-position of the scaffold was found to be crucial for the CA-III inhibitory activity. Furthermore, replacement of the free amino group with an amide and urea group resulted in a significant reduction of activity (compounds 13c and 14c, Ki = 174.1 and 186.2 μM, respectively). Thus, compound 12a (2-amino-5-phenylthiazole-4-carboxylic acid) can be considered as the lead molecule for further modification and development of more potent CA-III inhibitors.

CAIII expression in skeletal muscle is regulated by Ca2+–CaMKII–MEF2C signaling

Carbonic anhydrase III (CAIII) is selectively expressed in slow-twitch myofibers in skeletal muscle. The fast-twitch to slow-twitch transformation of myofibers following denervation is accompanied by increased CAIII expression, suggesting that the effects of nerve impulses on skeletal-muscle remodeling influence CAIII expression. Here, we determined the molecular mechanisms underlying the effects of nerve conduction on CAIII expression. The results indicated that changes in skeletal-muscle [Ca2+]i altered CAIII expression. Moreover, results from the RNA-interference and over-expression experiments identified myocyte enhancer factor 2C (MEF2C) as the key transcription factor regulating [Ca2+]i-mediated changes in CAIII transcription. Additionally, chromatin immunoprecipitation experiments and luciferase assays confirmed MEF2C interaction and direct binding of the CAIII promoter between −416 and −200 base pair. Investigations of upstream cytoplasmic signaling pathways responsible for MEF2C activation revealed Ca2+/calmodulin-dependent protein kinase II (CaMKII) as the key factor involved in MEF2C-mediated regulation of CAIII expression. This study demonstrates that the Ca2+–CaMKII–MEF2C signaling pathway is the key factor involved in regulating CAIII expression in skeletal muscle. These results provide a theoretical basis supporting further investigations of changes in CAIII levels under different pathophysiological conditions and will facilitate a broader understanding of the biological functions of CAIII.

Transgenic expression of carbonic anhydrase III in cardiac muscle demonstrates a mechanism to tolerate acidosis.

Carbonic anhydrase III (CAIII) is abundant in liver, adipocytes, and skeletal muscles, but not heart. A cytosolic enzyme that catalyzes conversions between CO2 and in the regulation of intracellular pH, its physiological role in myocytes is not fully understood. Mouse skeletal muscles lacking CAIII showed lower intracellular pH during fatigue, suggesting its function in stress tolerance. We created transgenic mice expressing CAIII in cardiomyocytes that lack endogenous CAIII. The transgenic mice showed normal cardiac development and life span under nonstress conditions. Studies of ex vivo working hearts under normal and acidotic conditions demonstrated that the transgenic and wild-type mouse hearts had similar pumping functions under normal pH. At acidotic pH, however, CAIII transgenic mouse hearts showed significantly less decrease in cardiac function than that of wild-type control as shown by higher ventricular pressure development, systolic and diastolic velocities, and stroke volume via elongating the time of diastolic ejection. In addition to the effect of introducing CAIII into cardiomyocytes on maintaining homeostasis to counter acidotic stress, the results demonstrate the role of carbonic anhydrases in maintaining intracellular pH in muscle cells as a potential mechanism to treat heart failure.

The relationship between carbonic anhydrase-III expression and oxidative stress in brown adipose tissue

Objective:
 High-fat foods increase adipose tissue size, and induce obesity. Although
 carbonic anhydrase III is abundantly found in brown adipose tissue, its
 function is not fully defined. In this study, we investigated the relationship
 between carbonic anhydrase III enzyme mRNA expression and malondialdehyde,
 oxidative stress marker, in brown adipose tissue of rats that were fed high-fat
 diets. In addition, we investigated potential effect of N-acetylcysteine as an
 antioxidant in this relationship. 
 
 Methods: In
 our study three experimental groups were formed and each contained 6 rats
 (control, obese, and antioxidant groups). The experimental groups were fed for
 a duration of 85 days with high fat diets. In these groups, carbonic anhydrase
 III mRNA expression, total carbonic anhydrase hydratase activitie, and
 malondialdehyde levels were measured in brown adipose tissues dissected from
 rat scapula regions.
 
 Results:
 According to our findings, carbonic anhydrase III mRNA expression was higher in
 the obese group than in the control group (p = 0.004), and malondialdehyde
 levels were lower in the obese group than in the control group (p = 0.03). It
 was observed that carbonic anhydrase III mRNA expression was higher in the
 antioxidant group than in the control group (p = 0.006), and malondialdehyde
 levels were lower in the antioxidant group than in the control group (p =
 0.006). In addition, in the obese group carbonic anhydrase III mRNA expression
 was higher than in the antioxidant group (p=0.01). 
 
 Conclusion:
 In brown adipose tissue of rats that were fed high-fat diets, this study showed
 that the carbonic anhydrase III mRNA expression increased and the
 malondialdehyde level decreased.

The Impact of EVI1 on Carbonic Anhydrase III Expression and the Sensitivity of Rat1 Fibroblasts to H2O2-induced Apoptosis

EVI1 is a transcriptional factor with two distinct zinc finger domains and encoded in human chromosome 3q26. In human, the protein is believed to have role in cell proliferation, organogenesis and it was detected in kidneys and lungs. EVI1 overexpression has been associated with various conditions such as myelodysplastic syndrome (MDS), juvenile myelomonocytic leukaemia (JMML) and acute myeloid leukaemia (AML). In the present study, Carbonic Anhydrase III (CaIII) was expressed at much lower levels in EVI1 overexpressing fibroblast cells compared to the wild type indicating an inhibitory role of EVI1 against CaIII. Our results were further confirmed by western blot in which CaIII protein in normal fibroblast cells was more abundance than that in cells with EVI1 enforced expression. Furthermore, Luciferase reporter assay showed repressed promotor activity in EVI1 overexpressing cells resulted from EVI1 interfering with CaIII promotor by direct or indirect binding. Fibroblast cells with repressed CaIII showed higher sensitivity to apoptosis induced by hydrogen peroxide, this is attributed to the downregulation of CaIII gene which has a defensive role against the oxidative damage. It has been reported that the CaIII overexpression increases the cell resistance against the oxidative stress caused by exposure to H2O2. Thus, elevated EVI1 levels repress CaIII expression leading to increased cell sensitivity to H2O2-induced apoptosis. These findings seem to be constant with previous studies, and might introduce a novel approach to treat leukaemia depending on H2O2-induced apoptosis.

Expression of Carbonic Anhydrase III, a Nucleus Pulposus Phenotypic Marker, is Hypoxia-responsive and Confers Protection from Oxidative Stress-induced Cell Death

The integrity of the avascular nucleus pulposus (NP) phenotype plays a crucial role in the maintenance of intervertebral disc health. While advances have been made to define the molecular phenotype of healthy NP cells, the functional relevance of several of these markers remains unknown. In this study, we test the hypothesis that expression of Carbonic Anhydrase III (CAIII), a marker of the notochordal NP, is hypoxia-responsive and functions as a potent antioxidant without a significant contribution to pH homeostasis. NP, but not annulus fibrosus or end-plate cells, robustly expressed CAIII protein in skeletally mature animals. Although CAIII expression was hypoxia-inducible, we did not observe binding of HIF-1α to select hypoxia-responsive-elements on Car3 promoter using genomic chromatin-immunoprecipitation. Similarly, analysis of discs from NP-specific HIF-1α null mice suggested that CAIII expression was independent of HIF-1α. Noteworthy, silencing CAIII in NP cells had no effect on extracellular acidification rate, CO2 oxidation rate, or intracellular pH, but rather sensitized cells to oxidative stress-induced death mediated through caspase-3. Our data clearly suggests that CAIII serves as an important antioxidant critical in protecting NP cells against oxidative stress-induced injury.

Expression of carbonic anhydrase III and skeletal muscle remodeling following selective denervation.

Carbonic anhydrase III (CAIII) is expressed selectively in type I(slow‑twitch) myofibers. To investigate the association between changes in the expression of CAIII and skeletal muscle structure following denervation, the present study stained adjacent sections of skeletal muscle for ATPase and immunohistochemically for CAIII. In addition, differences in the protein expression and phosphatase activity of CAIII were examined by western blot and phosphatase staining between rat soleus and extensol digitorum longus (EDL) muscles, which are composed of predominantly slow‑ and fast‑twitch fibers, respectively. Upon denervation, the EDL muscle showed more pronounced structural changes, compared with the soleus muscle. There was a transformation from fast to slow fibers, and a concomitant increase in fibers positive for CAIII. Following denervation, the protein expression of CAIII initially increased and then decreased in the soleus muscle, whereas the protein expression of CAIII in the EDL muscle increased gradually with time. In contrast to the protein changes, phosphatase activity in the soleus and EDL muscles decreased significantly following denervation. These results indicated that, following denervation, changes in the expression of CAIII were associated with myofiber remodeling. Specifically, the change in the expression of CAIII reflected the conversion to type I myofibers, suggesting the importance of CAIII in resistance to fatigue in skeletal muscle.

Carbonic anhydrase III protects osteocytes from oxidative stress.

Osteocytes are master orchestrators of bone remodeling; they control osteoblast and osteoclast activities both directly via cell-to-cell communication and indirectly via secreted factors, and they are the main postnatal source of sclerostin and RANKL (receptor activator of NF-kB ligand), two regulators of osteoblast and osteoclast function. Despite progress in understanding osteocyte biology and function, much remains to be elucidated. Recently developed osteocytic cell lines-together with new genome editing tools-has allowed a closer look at the biology and molecular makeup of these cells. By using single-cell cloning, we identified genes that are associated with high Sost/sclerostin expression and analyzed their regulation and function. Unbiased transcriptome analysis of high- vs. low-Sost/sclerostin-expressing cells identified known and novel genes. Dmp1 (dentin matrix protein 1), Dkk1 (Dickkopf WNT signaling pathway inhibitor 1), and Phex were among the most up-regulated known genes, whereas Srpx2, Cd200, and carbonic anhydrase III (CAIII) were identified as novel markers of differentiated osteocytes. Aspn, Enpp2, Robo2, Nov, and Serpina3g were among the transcripts that were most significantly suppressed in high-Sost cells. Considering that CAII was recently identified as being regulated by Sost/sclerostin and capable of controlling mineral homeostasis, we focused our attention on CAIII. Here, we report that CAIII is highly expressed in osteocytes, is regulated by parathyroid hormone both in vitro and in vivo, and protects osteocytes from oxidative stress.-Shi, C., Uda, Y., Dedic, C., Azab, E., Sun, N., Hussein, A. I., Petty, C. A., Fulzele, K., Mitterberger-Vogt, M. C., Zwerschke, W., Pereira, R., Wang, K., Divieti Pajevic, P. Carbonic anhydrase III protects osteocytes from oxidative stress.

Effects of pepsin A on heat shock protein 70 response in laryngopharyngeal reflux patients with chronic rhinosinusitis

Objectives: We investigated the relationship between laryngopharyngeal reflux (LPR) and chronic rhinosinusitis (CRS), and explored the effects of pepsin A on the level of heat shock protein 70 (HSP70) in CRS.Methods: We included 23 CRS patients with nasal polyps (CRSwNP), 26 CRS patients without nasal polyps (CRSsNP) and nine normal controls to measure pepsin A levels in nasal secretions, blood plasma and nasal tissues, to measure HSP70 levels in nasal tissues, and to detect pepsinogen A, HSPA5, cyclo-oxygenase-2 (COX-2), and carbonic anhydrase III (CAIII) mRNA expression levels in nasal tissues.Results: Pepsin A levels in nasal secretions were significantly higher in CRSwNP/CRSsNP patients than in controls. HSP70 levels were significantly increased in pepsin A-positive turbinate mucosa compared to controls (p < .001). Similarly, HSP70 levels were significantly increased in pepsin A-positive polyp tissues than in pepsin A-negative polyp tissues (p = .016). Furthermore, no association was found between the presence of pepsin A and HSPA5, COX-2, and CAIII mRNA expression levels.Conclusions: These results suggest that LPR may play a role in the development of CRS through pepsin A reflux, and increased HSP70 expression may be associated with the pathogenic mechanism of mucosal injury in CRS.

6-Substituted nicotinic acid analogues, potent inhibitors of CAIII, used as therapeutic candidates in hyperlipidemia and cancer

Nicotinic acid has been reported as a potential inhibitor of carbonic anhydrase III enzyme. Carbonic anhydrase III (CAIII) is an emerging new pharmacological target for the management of dyslipidemia and cancer progression. The activity of 6-substituted nicotinic acid analogs against carbonic anhydrase III was studied using a size-exclusion chromatography. The appearance of concentration-dependent vacancy peak was indicative of binding with CAIII. Chromatographic and docking studies revealed that the carboxylic acid of ligand is essential for binding via coordinate bond formation with Zn+2 ion in the enzyme active site. Moreover, the presence of a hydrophobic group, containing a hydrogen bond acceptor, at position 6 of the pyridine improves activity, e.g., 6-(hexyloxy) pyridine-3-carboxylic acid (Ki = 41.6 µM). Utilizing the weak esterase activity of CAIII, the inhibitory mode of 6-substituted nicotinic acid was confirmed.

Carbonic Anhydrase III Is Expressed in Mouse Skeletal Muscles Independent of Fiber Type-Specific Myofilament Protein Isoforms and Plays a Role in Fatigue Resistance.

Carbonic anhydrase III (CAIII) is a metabolic enzyme and a regulator for intracellular pH. CAIII has been reported with high level expression in slow twitch skeletal muscles. Here we demonstrate that CAIII is expressed in multiple slow and fast twitch muscles of adult mouse independent of the expression of myosin isoforms. Expressing similar fast type of myofilament proteins, CAIII-positive tibial anterior (TA) muscle exhibits higher tolerance to fatigue than that of CAIII-negative fast twitch extensor digitorum longus (EDL) muscle in in situ contractility studies. We further studied the muscles of CAIII knockout (Car3-KO) mice. The loss of CAIII in soleus and TA muscles in Car3-KO mice did not change muscle mass, sarcomere protein isoform contents, and the baseline twitch and tetanic contractility as compared with age-matched wild type (WT) controls. On the other hand, Car3-KO TA muscle showed faster force reduction at the beginning but higher resistance at the end during a fatigue test, followed by slower post fatigue recovery than that of WT TA muscle. Superfused Car3-KO soleus muscle also had faster total force reduction during fatigue test than that of WT soleus. However, it showed a less elevation of resting tension followed by a better post fatigue recovery under acidotic stress. CAIII was detected in neonatal TA and EDL muscle, downregulated during development, and then re-expressed in adult TA but not EDL muscles. The expression of CAIII in Tnnt1-KO myopathy mouse soleus muscle that has diminished slow fiber contents due to the loss of slow troponin T remained high. Car3-KO EDL, TA, and soleus muscles showed no change in the expression of mitochondria biomarker proteins. The data suggest a fiber type independent expression of CAIII with a role in the regulation of intracellular pH in skeletal muscle and may be explored as a target for improving fatigue resistance and for the treatment of TNNT1 myopathies.

Improved serological detection of rheumatoid arthritis: a highly antigenic mimotope of carbonic anhydrase III selected in a murine model by phage display.

IntroductionRheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that affects around 1 % of the human population worldwide. RA diagnosis can be difficult as there is no definitive test for its detection. Therefore, the aim of this study was to identify biomarkers that could be used for RA diagnosis.MethodsSera from a collagen-induced arthritis mouse model were used to select potential biomarkers for RA diagnosis by phage display technology. In silico and in vitro analyses were performed to characterize and validate the selected peptides. Samples were classified into three groups: RA; two other immune-mediated rheumatic diseases (systemic lupus erythematosus (SLE) and ankylosing spondylitis (AS)); and healthy controls (HC). Enzyme-linked immunosorbent assay (ELISA) was carried out to determine antibody levels, and diagnostic parameters were determined by constructing receiver operating characteristic curves. Mass spectrometry and Western blot were performed to identify the putative autoantigen that was mimicked by a highly reactive mimotope.ResultsAfter three rounds of selection, 14 clones were obtained and tested for immunoreactivity analysis against sera from RA and HC groups. The phage-fused peptide with the highest immunoreactivity (M12) was synthesized, and was able to efficiently discriminate RA patients from SLE, AS and HCs (p < 0.0001) by ELISA. The specificity and sensitivity of anti-M12 antibodies for RA diagnosis were 91 % and 84.3 %, respectively. The M12 peptide was identified as one that mimics a predicted antigenic site of the carbonic anhydrase III (CAIII) protein, a ubiquitous biomarker that has been identified in patients with other diseases.ConclusionM12 is the first peptide associated with the CAIII protein that may be used as an antigen for antibody detection to aid in RA diagnosis with high sensitivity and specificity.

Isoaspartate, carbamoyl phosphate synthase-1, and carbonic anhydrase-III as biomarkers of liver injury

We had previously shown that alcohol consumption can induce cellular isoaspartate protein damage via an impairment of the activity of protein isoaspartyl methyltransferase (PIMT), an enzyme that triggers repair of isoaspartate protein damage. To further investigate the mechanism of isoaspartate accumulation, hepatocytes cultured from control or 4-week ethanol-fed rats were incubated in vitro with tubercidin or adenosine. Both these agents, known to elevate intracellular S-adenosylhomocysteine levels, increased cellular isoaspartate damage over that recorded following ethanol consumption in vivo. Increased isoaspartate damage was attenuated by treatment with betaine. To characterize isoaspartate-damaged proteins that accumulate after ethanol administration, rat liver cytosolic proteins were methylated using exogenous PIMT and 3H-S-adenosylmethionine and proteins resolved by gel electrophoresis. Three major protein bands of ∼75–80 kDa, ∼95–100 kDa, and ∼155–160 kDa were identified by autoradiography. Column chromatography used to enrich isoaspartate-damaged proteins indicated that damaged proteins from ethanol-fed rats were similar to those that accrued in the livers of PIMT knockout (KO) mice. Carbamoyl phosphate synthase-1 (CPS-1) was partially purified and identified as the ∼160 kDa protein target of PIMT in ethanol-fed rats and in PIMT KO mice. Analysis of the liver proteome of 4-week ethanol-fed rats and PIMT KO mice demonstrated elevated cytosolic CPS-1 and betaine homocysteine S-methyltransferase-1 when compared to their respective controls, and a significant reduction of carbonic anhydrase-III (CA-III) evident only in ethanol-fed rats. Ethanol feeding of rats for 8 weeks resulted in a larger (∼2.3-fold) increase in CPS-1 levels compared to 4-week ethanol feeding indicating that CPS-1 accumulation correlated with the duration of ethanol consumption. Collectively, our results suggest that elevated isoaspartate and CPS-1, and reduced CA-III levels could serve as biomarkers of hepatocellular injury.