A Model for SARS-CoV-2 Infection with Treatment.

The current emergence of coronavirus (SARS-CoV-2) puts the world in threat. The structural research on the receptor recognition by SARS-CoV-2 has identified the key interactions between SARS-CoV-2 spike protein and its host (epithelial cell) receptor, also known as angiotensin-converting enzyme 2 (ACE2). It controls both the cross-species and human-to-human transmissions of SARS-CoV-2. In view of this, we propose and analyze a mathematical model for investigating the effect of CTL responses over the viral mutation to control the viral infection when a postinfection immunostimulant drug (pidotimod) is administered at regular intervals. Dynamics of the system with and without impulses have been analyzed using the basic reproduction number. This study shows that the proper dosing interval and drug dose both are important to eradicate the viral infection.

A Replication-Competent Vesicular Stomatitis Virus for Studies of SARS-CoV-2 Spike-Mediated Cell Entry and Its Inhibition.

There is an urgent need for vaccines and therapeutics to prevent and treat COVID-19. Rapid SARS-CoV-2 countermeasure development is contingent on the availability of robust, scalable, and readily deployable surrogate viral assays to screen antiviral humoral responses, define correlates of immune protection, and down-select candidate antivirals. Here, we generate a highly infectious recombinant vesicular stomatitis virus (VSV) bearing the SARS-CoV-2 spike glycoprotein S as its sole entry glycoprotein and show that this recombinant virus, rVSV-SARS-CoV-2 S, closely resembles SARS-CoV-2 in its entry-related properties. The neutralizing activities of a large panel of COVID-19 convalescent sera can be assessed in a high-throughput fluorescent reporter assay with rVSV-SARS-CoV-2 S, and neutralization of rVSV-SARS-CoV-2 S and authentic SARS-CoV-2 by spike-specific antibodies in these antisera is highly correlated. Our findings underscore the utility of rVSV-SARS-CoV-2 S for the development of spike-specific therapeutics and for mechanistic studies of viral entry and its inhibition.

Balancing Effect of Biejiajian Oral Liquid () on ACE-Ang II-AT1R Axis and ACE2-Ang-(1-7)-Mas Axis in Rats with CCl4-Induced Hepatic Fibrosis.

OBJECTIVE: To explore the effect of Biejiajian Oral Liquid (, BOL) on CCl4-induced hepatic fibrosis in rats by detecting the changes in the levels of angiotensin II (Ang II), angiotensin-(1-7) [Ang-(1-7)], angiotensin-converting enzyme (ACE), ACE2, angiotensin II type 1 receptor (AT1R), Mas, etc. METHODS: A total of 180 Wistar rats were randomly divided into two groups by random digital table method: prevention experiment and treatment experiment. Each group was further subdivided into the following 6 subgroups: normal control group, model group, vitamin E [100 mg/(kg·d), VE] group, enalapril [10 mg/(kg·g), Ena] group, high-dosage [20 g/(kg·d)] BOL group, and low-dosage [10 g/(kg·d)] BOL group. The hepatic fibrosis rat model was established by subcutaneous injection of CCl4 for 6 weeks. Prevention experiment and treatment experiment were administered with specific drugs at different times. At the end of treatment experiment, the pathological changes of liver were observed after hematoxylin-eosin staining. The expressions of ingredients in renin-angiotensin-aldosterone system (RAAS) such as AngII, Ang-(1-7), ACE, ACE2, AT1R, Mas, renin, CYP11B2 and angen in liver were detected by enzyme linked immunosorbent assay, immunohistochemistry method or reverse transcription-polymerase chain reaction, respectively. RESULTS: The levels of AngII and Ang-(1-7) at the 6th week increased by 496.10% and 73.64%, respectively, compared with those at the 2nd week in the model group (P<0.01). With prevention or treatment with high-dosage BOL, there was an evident reduction of AngII level but an improvement of Ang-(1-7) level. Specifically, AngII level of high-dosage group decreased by 77.50% in prevention experiment (P=0.000) and by 76.93% in treatment experiment (P=0.002) compared with that in the model group. Ang-(1-7) level increased by 91.69% in prevention experiment (P=0.006) and by 70.77% in the treatment experiment (P=0.010) compared with that in the model group. The expression levels of mRNA of renin, ACE, CYP11B2, angen and AT1R decreased by 58.15%, 99.90%, 99.84%, 99.99% and 99.99% (all P<0.01), respectively. CONCLUSIONS: BOL could help resist liver fibrosis in rats by enhancing the level of each ingredient in ACE2-Ang-(1-7)-Mas axis, while decreasing the level of each ingredient in ACE-AngII-AT1R axis. To some extent, BOL could enhance the regulation of RAAS in rats with CCl4-induced hepatic fibrosis.

Brain angiotensin-converting enzymes: role of angiotensin-converting enzyme 2 in processing angiotensin II in mice.

Angiotensin (Ang)-converting enzyme 2 (ACE2) metabolizes Ang II to the vasodilatory peptide Ang(1-7), while neprilysin (NEP) generates Ang(1-7) from Ang I. Experiments used novel Surface Enhanced Laser Desorption Ionization-Time of Flight (SELDI-TOF) mass spectroscopic (MS) assays to study Ang processing. Mass spectroscopy was used to measure proteolytic conversion of Ang peptide substrates to their specific peptide products. We compared ACE/ACE2 activity in plasma, brain and kidney from C57BL/6 and NEP(-/-) mice. Plasma or tissue extracts were incubated with Ang I or Ang II (1296 or 1045, m/z, respectively), and generated peptides were monitored with MS. Angiotensin-converting enzyme 2 activity was detected in kidney and brain, but not in plasma. Brain ACE2 activity was highest in hypothalamus. Angiotensin-converting enzyme 2 activity was inhibited by the specific ACE2 inhibitor, DX600 (10 microm, 99% inhibition), but not by the ACE inhibitor, captopril (10 microm). Both MS and colorimetric assays showed high ACE activity in plasma and kidney with low levels in brain. To extend these findings, ACE measurements were made in ACE overexpressing mice. Angiotensin-converting enzyme four-copy mice showed higher ACE activity in kidney and plasma with low levels in hypothalamus. In hypothalamus from NEP-/- mice, generation of Ang(1-7) from Ang I was decreased, suggesting a role for NEP in Ang metabolism. With Ang II as substrate, there was no difference between NEP-/- and wild-type control mice, indicating that other enzymes may contribute to generation of Ang(1-7). The data suggest a predominant role of hypothalamic ACE2 in the processing of Ang II, in contrast to ACE, which is most active in plasma.

Angiotensin-converting enzyme inhibition modulates mitogen-activated protein kinase family expressions in the neonatal rat kidney.

Among the mitogen-activated protein kinase (MAPK) family members, extracellular signal-regulated kinase (ERK) promotes cell proliferation or differentiation, whereas c-jun N terminal kinase (JNK) and p38 MAPK are thought to inhibit cell growth and induce apoptosis. The MAPK family may plays some role during kidney development, when large-scale proliferation and apoptosis have been observed to occur. Also, in this period, the renin-angiotensin system is markedly activated. We have demonstrated that angiotensin-converting enzyme inhibition in the developing rat kidney increases apoptosis and decreases cell proliferation, which may account for renal growth impairment. The aim of this study, therefore, was to examine the relationship between the MAPK family and renin-angiotensin system during neonatal renal development. Newborn rat pups were treated with enalapril (30 mg . kg(-1) . d(-1)) or normal saline for 7 d. Right kidneys of both groups were selected for immunohistochemical stains of MAPKs and activating transcription factor-2 (ATF-2), and left kidneys were selected for reverse transcriptase-PCR and immunoblot analysis of MAPKs, phospho-MAPKs, and ATF-2. To determine whether apoptosis is involved in the same tubules that highly expressed JNK and p38, we performed terminal deoxynucleotide transferase-mediated nick-end labeling stain for apoptotic cells and immunohistochemical stains for JNK-2, p38, and ATF-2 expression in the serial sections from the same kidney of the enalapril-treated group. In the enalapril-treated group, JNK-2, p38, phospho-JNK-2, phospho-p38, and ATF-2 protein expressions were significantly increased, and their immunoactivities were strongly detected in the proximal tubular epithelial cells in the cortex, compared with the control group. Especially JNK-2 and p38 expressions were highly activated and were spatially in accordance with the occurrence of apoptosis. ERK1/2 and phospho-ERK expressions were not changed by enalapril. These results suggest that the expressions of the MAPK family are modulated by angiotensin-converting enzyme inhibition in the developing kidney. JNK and p38 may be implicated to participate in angiotensin II-related intracellular signaling pathways of renal apoptosis in the developing kidney.

Modulation of cutaneous inflammation by angiotensin-converting enzyme.

Cutaneous neurogenic inflammation is a complex biological response of the host immune system to noxious stimuli. Present evidence suggests that zinc metalloproteases may play an important role in the regulation of neurogenic inflammation by controlling the local availability of neuropeptides, such as substance P (SP), that are capable of initiating or amplifying cutaneous inflammation after release from sensory nerves. To address the hypothesis that the dipeptidyl carboxypeptidase angiotensin-converting enzyme (ACE) is capable of modulating skin inflammation, we have analyzed murine allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD) using wild-type C57BL/6J (ACE(+/+)) or genetically engineered mice with a heterozygous deletion of somatic ACE (ACE(+/-)). In 2,4-dinitro-1-fluorobenzene-sensitized ACE(+/-) mice, ACD was significantly augmented in comparison to ACE(+/+) controls as determined by the degree of ear swelling after exposure to hapten. Likewise, systemic treatment of ACE(+/+) mice with the ACE inhibitor captopril before sensitization or elicitation of ACD significantly augmented the ACD response. In contrast, local damage and neuropeptide depletion of sensory nerves following capsaicin, injection of a bradykinin B(2), or a SP receptor antagonist before sensitization significantly inhibited the augmented effector phase of ACD in mice with functionally absent ACE. However, in contrast to ACD, the response to the irritant croton oil was not significantly altered in ACE(+/-) compared with ACE(+/+) mice. Thus, ACE by degrading bradykinin and SP significantly controls cutaneous inflammatory responses to allergens but not to irritants, which may explain the frequently observed exacerbation of inflammatory skin disease in patients under medication with ACE inhibitors.

Action of three ectopeptidases on corticotropin-releasing factor: metabolism and functional aspects.

Using purified enzyme preparations, we investigated the actions of angiotensin-converting enzyme, aminopeptidase N, and endopeptidase 24.11 on corticotropin-releasing factor (CRF). The effects of inhibition of these enzymes on CRF action in rat anterior pituitary cultures were also determined. Finally, specific inhibitors were used to evaluate ectopeptidase action on the regional brain metabolism of CRF. K(m) values for CRF were 165, 90, and 42 microM for angiotensin-converting enzyme, aminopeptidase N, and endopeptidase 24.11, respectively. A CRF metabolite profile for each enzyme was determined. In pituitary cultures, inhibition of endopeptidase 24.11 and aminopeptidase N potentiated CRF-stimulated release of adrenocorticotropic hormone (ACTH). In rat pituitary and hypothalamus membrane preparations, specific inhibitor experiments indicated that CRF hydrolysis involved members of the neutral endopeptidase and aminopeptidase enzyme families. In cortex membranes, similar peptidase inhibition was without effect. These data support the hypothesis that ectopeptidases play a major role in CRF metabolism and biological function.

Milk protein-derived peptide inhibitors of angiotensin-I-converting enzyme.

Numerous casein and whey protein-derived angiotensin-I-converting enzyme (ACE) inhibitory peptides/hydrolysates have been identified. Clinical trials in hypertensive animals and humans show that these peptides/hydrolysates can bring about a significant reduction in hypertension. These peptides/hydrolysates may be classified as functional food ingredients and nutraceuticals due to their ability to provide health benefits i.e. as functional food ingredients in reducing the risk of developing a disease and as nutraceuticals in the prevention/treatment of disease.

Race: a Drosophila homologue of the angiotensin converting enzyme.

We report the isolation and characterization of a putative angiotensin converting enzyme (ACE) in Drosophila, called Race. General interest in mammalian ACE stems from its association with high blood pressure; ACE has also been implicated in a variety of other physiological processes including the processing of neuropeptides and gut peristalsis. Mammalian ACE is a membrane associated zinc binding protease that converts angiotensin I (A I) into angiotensin II (A II). A II functions as a potent vasoconstrictor by triggering a G-coupled receptor system in the smooth muscles that line blood vessels. Drosophila Race is composed of 615 amino acid residues, and shares extensive sequence identity with mammalian ACE over its entire length (over 42% overall identity and greater than 60% similarity). Evidence is presented that Race might correspond to a target of the homeobox regulatory gene, zerknullt (zen). Soon after zen expression is restricted to the dorsal-most regions of the embryonic ectoderm, Race is activated in a coincident pattern and becomes associated with the amnioserosa during germ band elongation, shortening and heart morphogenesis. After germ band elongation, Race is also expressed in both the anterior and posterior midgut, where it persists throughout embryogenesis. Race expression is lost from the dorsal ectoderm in either zen- or dpp- mutants, although gut expression is unaffected. P-transformation assays and genetic complementation tests suggest that Race corresponds to a previously characterized lethal complementation group, 1(2)34Eb. Mutants die during larval/pupal development, and transheterozygotes for two different lethal alleles exhibit male sterility. We propose that Race might play a role in the contractions of the heart, gut, or testes and also suggest that Hox genes might be important for coordinating both developmental and physiological processes.