Clinical significance of serum microRNA-146a and inflammatory factors in children with Mycoplasma pneumoniae pneumonia after azithromycin treatment.

OBJECTIVE: This study aimed to investigate the clinical significance of serum microRNA-146a and pro-inflammatory factors in children with Mycoplasma pneumoniae pneumonia after azithromycin treatment. microRNA-146a is known to regulate inflammatory responses, and excessive inflammation is a primary characteristic of MPP. METHODS: Children with MPP received conventional symptomatic therapy along with intravenous administration of azithromycin for one week. Serum levels of microRNA-146a and pro-inflammatory factors were measured using RT-qPCR and ELISA kits, respectively. The correlation between microRNA-146a and pro-inflammatory factors was analyzed by the Pearson method. Pulmonary function indexes were assessed using a pulmonary function analyzer, and their correlation with microRNA-146a and pro-inflammatory factors after treatment was evaluated. Children with MPP were divided into effective and ineffective treatment groups, and the clinical significance of microRNA-146a and pro-inflammatory factors was evaluated using receiver operating characteristic curves and logistic multivariate regression analysis. RESULTS: Serum microRNA-146a was downregulated in children with MPP but upregulated after azithromycin treatment, contrasting with the trend observed for pro-inflammatory factors. MicroRNA-146a showed a negative correlation with pro-inflammatory cytokines. Pulmonary function parameters were initially reduced in children with MPP, but increased after treatment, showing positive/inverse associations with microRNA-146a and pro-inflammatory factors. Higher microRNA-146a and lower pro-inflammatory factors predicted better efficacy of azithromycin treatment. MicroRNA-146a, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-8 (IL-8), and forced expiratory volume in the first second/forced vital capacity (FEV1/FVC) were identified as independent factors influencing treatment efficacy. CONCLUSION: Azithromycin treatment in children with MPP upregulates microRNA-146a, downregulates pro-inflammatory factors, and effectively improves pulmonary function.

Clinical significance of serum microRNA-146a and inflammatory factors in children with Mycoplasma pneumoniae pneumonia after azithromycin treatment

Abstract Objective This study aimed to investigate the clinical significance of serum microRNA-146a and pro-inflammatory factors in children with Mycoplasma pneumoniae pneumonia after azithromycin treatment. microRNA-146a is known to regulate inflammatory responses, and excessive inflammation is a primary characteristic of MPP. Methods Children with MPP received conventional symptomatic therapy along with intravenous administration of azithromycin for one week. Serum levels of microRNA-146a and pro-inflammatory factors were measured using RT-qPCR and ELISA kits, respectively. The correlation between microRNA-146a and pro-inflammatory factors was analyzed by the Pearson method. Pulmonary function indexes were assessed using a pulmonary function analyzer, and their correlation with microRNA-146a and pro-inflammatory factors after treatment was evaluated. Children with MPP were divided into effective and ineffective treatment groups, and the clinical significance of microRNA-146a and pro-inflammatory factors was evaluated using receiver operating characteristic curves and logistic multivariate regression analysis. Results Serum microRNA-146a was downregulated in children with MPP but upregulated after azithromycin treatment, contrasting with the trend observed for pro-inflammatory factors. MicroRNA-146a showed a negative correlation with pro-inflammatory cytokines. Pulmonary function parameters were initially reduced in children with MPP, but increased after treatment, showing positive/inverse associations with microRNA-146a and pro-inflammatory factors. Higher microRNA-146a and lower pro-inflammatory factors predicted better efficacy of azithromycin treatment. MicroRNA-146a, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), interleukin-8 (IL-8), and forced expiratory volume in the first second/forced vital capacity (FEV1/FVC) were identified as independent factors influencing treatment efficacy. Conclusion Azithromycin treatment in children with MPP upregulates microRNA-146a, downregulates pro-inflammatory factors, and effectively improves pulmonary function.

Arginine vasopressin injection rescues delayed oviposition in cyp19a1b-/- mutant female zebrafish.

In zebrafish, estrogens produced in the ovaries via Cyp19a1a activity are required for both sexual differentiation of the ovary during early development as well as maintenance of the ovarian state during adulthood. The importance of Cyp19a1b that is highly expressed in the brain for female reproduction is still under study. We previously reported that female cyp19a1b -/- mutant zebrafish have significantly lower brain estradiol levels and impaired spawning behavior characterized by an increased latency to oviposition during dyadic sexual behavior encounters. In the current study, we provide evidence that the delayed oviposition in female cyp19a1b -/- mutants is linked to impaired arginine vasopressin (Avp) signaling. Droplet digital PCR experiments revealed that levels of the estrogen receptors, avp, and oxytocin (oxt) are lower in the hypothalamus of mutant females compared to wildtype fish. We then used acute intraperitoneal injections of Avp and Oxt, along with mixtures of their respective receptor antagonists, to determine that Avp can uniquely rescue the delayed oviposition in female cyp19a1b -/- mutants. Using immunohistochemistry, we demonstrated that Cyp19a1b-expressing radial glial cell (RGC) fibers surround and are in contact with Avp-immunopositive neurons in the preoptic areas of the brain. This could provide the neuroanatomical proximity for RGC-derived estrogens to diffuse to and activate estrogen receptors and regulate avp expression levels. Together these findings identify a positive link between Cyp19a1b and Avp for female zebrafish sexual behavior. They also suggest that the female cyp19a1b -/- mutant behavioral phenotype is likely a consequence of impaired processing of Avp-dependent social cues important for mate identification and assessment.

Simultaneous extraction and detection of peptides, steroids, and proteins in small tissue samples.

The detection and quantification of hormones are important to assess the reproductive and stress status of experimental models and for the diagnosis of diseases in human and veterinary clinics. Traditionally, steroid, peptide, and protein hormones are analyzed in individual experiments using different extraction methodologies. With the new advancement on HPLC sorbents, the simultaneous measurement of hormones from different categories becomes possible. In this study, we present a novel sample processing strategy for the simultaneous extraction and detection of peptides, steroids, and proteins using high-resolution liquid chromatography tandem mass spectrometry. We demonstrate the sensitivity of our method for small tissues by acquiring data from brain, pituitary gland, and gonads of single zebrafish samples. This approach promises to shed light on the hormonal pathways and their interrelationships, providing knowledge on the integration of hormone systems.

Mutation of brain aromatase disrupts spawning behavior and reproductive health in female zebrafish.

Aromatase (Cyp19a1) is the steroidogenic enzyme that converts androgens into bioactive estrogens, and hence is in a pivotal position to mediate reproduction and sexual behavior. In teleosts, there are two aromatase paralogs: cyp19a1a that is highly expressed in granulosa and Leydig cells in the gonads with critical function in sexual differentiation of the ovary, and cyp19a1b that is highly expressed in radial glial cells in the brain with unknown roles in reproduction. Cyp19a1 -/- mutant zebrafish lines were used to investigate the importance of the cyp19a1 paralogs for spawning behavior and offspring survival and early development. Mutation of cyp19a1b was found to increase the latency to the first oviposition in females. Mutation of cyp19a1b in females also increased the number of eggs spawned; however, significantly more progeny died during early development resulting in no net increase in female fecundity. This finding suggests a higher metabolic cost of reproduction in cyp19a1b -/- mutant females. In males, the combined mutation of both cyp19a1 paralogs resulted in significantly lower progeny survival rates, indicating a critical function of cyp19a1 during early larval development. These data establish the specific importance of cyp19a1b for female spawning behavior and the importance of the cyp19a1 paralogs for early larval survival.

Clinical characterization of polycythemia vera associated with IgA nephropathy in a single Chinese center: A case series.

BACKGROUND: Polycythemia vera (PV) is a myeloproliferative neoplasm which is characterized by excessive production of erythrocytes as well as myeloid and megakaryocytic proliferation. PV associated with IgA nephropathy (IgAN) has rarely been reported in the literature. The long-term renal prognosis of these patients is unknown. METHODS: Clinical and pathological characteristics of 7 patients with renal biopsy-proven IgAN associated with PV were retrospectively analyzed. RESULTS: The 7 patients were all males, with a mean age of 49.1 ±â€…18.8 years when admitted to our hospital. Systemic symptoms include: hypertension in case 2, 3, 5, and 6, splenomegaly in case 2, 4, and 5, and multiple lacunar infarction in case 6. Bone marrow biopsy test revealed relative erythroid hyperplasia and atypical megakaryocyte proliferation which consistent with a chronic myeloproliferative neoplasm. All patients had JAK2V617F and BCR-ABL tested, and JAK2V617F positive in 2 patients. Mild mesangial proliferation was observed in 5 patients and moderate/severe mesangial proliferation in 2patients. Immunofluorescence mainly showed diffuse granular deposition of dominant IgA in mesangium. After follow-up of 56.7 ±â€…44.0 months, hemoglobin level was 144 ±â€…29 g/L and hematocrit lever was 0.470 ±â€…0.03, compared with 187 ±â€…29 g/L and 0.563 ±â€…0.087 respectively when admitted to our hospital. The urine protein was 0.85 ±â€…0.64 g/24 h compared with 3.97 ±â€…4.68 g/24 h. Case 3 progressed to end stage renal disease and had received hemodialysis for 5 years before renal transplantation. CONCLUSIONS: The results of this study showed that PV associated with IgAN mainly occurs in males and is often accompanied by hematuria and mild-to-moderate renal insufficiency. The long-term prognosis was good for most patients, and few progressed relatively quickly to end stage renal disease.

The role of glomerular lesions in the prognosis of patients with acute kidney injury during hemorrhagic fever with renal syndrome.

OBJECTIVE: This study aimed to explore the role of glomerular lesions in patients who suffered from acute kidney injury (AKI) during hemorrhagic fever with renal syndrome (HFRS). METHODS: The study comprised 66 patients with AKI during HFRS treated at the National Clinical Research Center of Kidney Diseases of China, Jinling Hospital, from January 2014 to December 2018. According to the kidney pathological findings, the 66 patients were divided into two groups: the tubulointerstitial injury group (HFRS-TI group, n = 43) and the tubulointerstitial injury with glomerular lesions group (HFRS-GL group, n = 23). The clinical and pathological characteristics of the 66 patients were analyzed. RESULTS: There were 9 cases of IgA nephropathy, 1 case of membranous nephropathy, 2 cases of diabetic nephropathy, and 11 cases of mesangial proliferative glomerulonephritis in the HFRS-GL group. There were more males in the HFRS-GL group than in the HFRS-TI group (92.3% vs. 69.8%, p < .05). A higher proportion of interstitial fibrosis (56.5% vs. 27.9%, p < .05) and more immunoglobulin and complement depositions (p < .001) were observed in the HFRS-GL group than in the HFRS-TI group. Rates of remission of AKI were lower in the HFRS-GL group than in the HFRS-TI group (73.9% vs. 95.3%, p < .05). The presence of glomerular lesions (HR = 5.636, 95% CI = 1.121-28.329, p = .036) and moderate tubulointerstitial injury (HR = 3.598, 95% CI = 1.278-10.125, p = .015) were found to be independent risk factors for kidney prognosis. CONCLUSIONS: Patients with AKI during HFRS can have glomerular lesions or glomerulonephritis. Patients with AKI during HFRS who have glomerular lesions or moderate renal tubulointerstitial injury proven by kidney biopsy have a relatively poor kidney prognosis. A kidney biopsy can help determine long-term prognosis in patients with AKI during HFRS.

Applying contrast-enhanced ultrasound model to distinguish atypical focal adenomyosis from uterine leiomyomas.

Background: Different from conventional ultrasound, contrast-enhanced ultrasound (CEUS) is better in observing microperfusion. For atypical focal adenomyosis and uterine leiomyomas that are difficult to be distinguished by conventional ultrasound, this study aims to further improve the differential diagnosis performance by using CEUS model. Methods: After screening the cases with difficulties in identifying focal myometrium lesions through conventional ultrasound, the number of cases covered in the focal adenomyosis group and leiomyomas group were 60 and 30 in derivation cohort, 14 and 7 in validation cohort. The qualitative and quantitative characteristics of CEUS were analyzed according to the surgical pathology. The qualitative characteristics include: the enhancement level based on the myometrium, the contrast enhancement pattern, the enhanced time of the lesion based on the myometrium, post-contrast lesion border, the distribution of the contrast agent, and the wash-out time based on the myometrium. The quantitative characteristics include: arrive time (AT), time to peak (TTP), peak intensity (PI), ΔAT, ΔTTP, ΔPI, |ΔAT|, |ΔTTP|, |ΔPI| and lesion temporal variability. Multiple logistic regression analysis was used to screen the independent risk factors, and a risk prediction model for the differential diagnosis of the two diseases was established. The area under the receiver operating characteristic (ROC) curve (AUC) was used to assess the diagnostic performance of the model. The validation cohort was used to further evaluate the diagnostic performance of the model. Results: Through the multivariate analysis, it concluded that short-term vessels first enhanced enhancement mode, unclear boundary, lesion temporal variability under CEUS >9.5 s, uneven contrast agent distribution could be independent risk factors for the diagnosis of adenomyosis [AUC =0.908, 95% confidence interval (CI): 0.833-0.982]. We also determined the sensitivity (98.33%), specificity (70.00%), positive predictive value (PPV) (86.76%), negative predictive value (NPV) (95.45%), and accuracy (87.78%) of this model. Based on pathological diagnosis, the sensitivity and specificity of the model in the validation cohort were both 85.71%, with NPV of 75% and PPV of 92.3%. The area under the ROC curve was 0.898 (95% CI: 0.742-1.000). Conclusions: The establishment of CEUS model has certain clinical application value in differentiating atypical focal adenomyosis from leiomyomas.

Value of contrast-enhanced ultrasound in diagnosis and differential diagnosis of polypoid lesions of gallbladder ≥ 1 cm.

OBJECTIVES: To evaluate the usefulness of Contrast-enhanced ultrasound (CEUS) in the diagnosis and differential diagnosis of Polypoid lesions of gallbladder (PLGs) ≥ 1 cm. METHODS: A prospective analysis was performed on 180 patients with PLGs ≥ 1 cm. 175 cases were confirmed by pathological diagnosis and the remaining were confirmed by other imaging findings. The characteristics of lesions on conventional Ultrasonography (US) and CEUS were recorded. RESULTS: Significant differences were observed in enhancement patterns between benign and malignant PLGs during both arterial (P < 0.001) and venous phases (P < 0.001). The malignant lesions typically yielded a "fast-in and fast-out" enhancement pattern. There was no significant difference in Arrival time (AT) between malignant and benign PLGs. If we consider wash-out time ≤ 40 s as a diagnostic standard for malignant lesions, the sensitivity, specificity, and accuracy were 88.24%, 85.62%, and 86.11%, respectively. Destruction of the Gallbladder (GB) wall was a particularly important indication of malignant PLGs, and the sensitivity, specificity, and accuracy were 93.33%, 92.12%, and 92.22%, respectively. The accuracy of CEUS in the diagnosis of PLGs, as well as malignant and benign lesions, was 92.22%, 92.47%, and 91.17%, respectively. CONCLUSIONS: The "fast-in and fast-out" enhancement pattern, hyper-enhancement in comparison to the GB wall in the arterial phase, wash-out time ≤ 40 s, GB wall destruction, and hepatic parenchymal infiltration are the characteristic findings of malignant PLGs. Besides, CEUS provides a valuable reference to classify some of the benign lesions.

Characteristics of hepatic solitary necrotic nodules on contrast-enhanced ultrasonography.

BACKGROUND: To summarize the characteristics of solitary necrotic nodules (SNN) in the liver observed under contrast-enhanced ultrasonography (CEUS). METHODS: Conventional ultrasonography (US) and CEUS were performed in 24 patients who were confirmed to have SNN by pathological assessment. The US data and dynamic enhancement patterns of CEUS were recorded and retrospectively analyzed. RESULTS: Ten of 24 patients underwent surgical resection, while the other 14 patients underwent a puncture biopsy to be confirmed as SNN. Among the 24 patients, 13 patients had a single lesion and 11 patients had multiple lesions. The largest lesion was selected for CEUS examination for patients with multiple lesions. Eleven patients presented no enhancement in all three phases, while the other 13 patients presented with a peripheral thin rim-like enhancement in the arterial phase, an iso-enhancement in the portal phase and delayed phase. However, no enhancement in the interior of the lesions was detected during three phases of CEUS. CONCLUSIONS: SNN has characteristic findings on the CEUS, which play an important role in the differential diagnoses of liver focal lesions.

Targeted mutation of secretogranin-2 disrupts sexual behavior and reproduction in zebrafish.

The luteinizing hormone surge is essential for fertility as it triggers ovulation in females and sperm release in males. We previously reported that secretoneurin-a, a neuropeptide derived from the processing of secretogranin-2a (Scg2a), stimulates luteinizing hormone release, suggesting a role in reproduction. Here we provide evidence that mutation of the scg2a and scg2b genes using TALENs in zebrafish reduces sexual behavior, ovulation, oviposition, and fertility. Large-scale spawning within-line crossings (n = 82 to 101) were conducted. Wild-type (WT) males paired with WT females successfully spawned in 62% of the breeding trials. Spawning success was reduced to 37% (P = 0.006), 44% (P = 0.0169), and 6% (P < 0.0001) for scg2a-/- , scg2b-/- , and scg2a-/-;scg2b-/- mutants, respectively. Comprehensive video analysis indicates that scg2a-/-;scg2b-/- mutation reduces all male courtship behaviors. Spawning success was 47% in saline-injected WT controls compared to 11% in saline-injected scg2a-/-;scg2b-/- double mutants. For these mutants, spawning success increased 3-fold following a single intraperitoneal (i.p.) injection of synthetic secretoneurin-a (P = 0.0403) and increased 3.5-fold with injection of human chorionic gonadotropin (hCG). Embryonic survival at 24 h remained on average lower in scg2a-/-;scg2b-/- fish compared to WT injected with secretoneurin-a (P < 0.001). Significant reductions in the expression of gonadotropin-releasing hormone 3 in the hypothalamus, and luteinizing hormone beta and glycoprotein alpha subunits in the pituitary provide evidence for disrupted hypothalamo-pituitary function in scg2a and scg2b mutant fish. Our results indicate that secretogranin-2 is required for optimal reproductive function and support the hypothesis that secretoneurin is a reproductive hormone.

Ser422 phosphorylation blocks human Tau cleavage by caspase-3: Biochemical implications to Alzheimer's Disease.

Proteolytic truncation of microtubule associated human (h) Tau protein by caspase-3 at the carboxy (C) terminus has been linked to the pathogenesis of Alzheimer's Disease (AD). This cleavage likely occurs between Asp421↓Ser422 leading to the formation of 421-mer truncated Tau protein which has been found to be present as aggregate in high level after phosphorylation in mortal AD brain tissue compared to normal. At least 50 phosphorylation sites involving Ser, Thr and Tyr residues have been identified or proposed in hTau and a selected number of them have been implicated in hTau aggregation following latter's proteolytic truncation. Interestingly, it is further noted that Ser422 residue present in the P1' position of hTau caspase-3 cleavage region is a potential phosphorylation site. So we became interested to examine in vitro the effect of phospho-Ser422 residue on hTau cleavage by caspase-3 which is a crucial upstream event associated with hTau self-assembly leading to AD pathogenesis. The goal of this project is to study in vitro the caspase-3 cleavage site of hTau protein and to examine the kinetics of this cleavage following Ser422 phosphorylation and treatment with caspase-3 inhibitors. This is achieved by designing peptides from the sequence of hTau protein containing the proposed caspase-3 cleavage region. Peptides were designed from 441-mer major human Tau protein sequence that encompasses the proposed caspase-3 cleavage site [Asp421↓Ser422]. Corresponding phospho-, dextro-Ser422 and dextro-Asp421 analogs were also designed. Peptides were synthesized by solid phase chemistry, purified and fully characterized by mass spectrometry. These were then incubated with recombinant caspase-3 enzyme under identical condition for digestion and analyzed for cleavage by mass spectrometry and RP-HPLC chromatograms. Our results indicated that while the control peptide is efficiently cleaved by caspase-3 at Asp421↓Ser422 site producing the expected N- and C-terminal fragment peptides, the corresponding phospho-Ser422 peptide remained completely resistant to the cleavage. Substitution of Asp421 by its dextro isoform also blocks peptide cleavage by caspase-3. However substitution of Ser422 by its dextro isoform in the peptide did not affect the cleavage significantly. The above results were further confirmed by caspase-3 digestion experiment in the presence of varying amounts of caspase-3 inhibitor (Ac-DQVD-aldehyde) which was found to block this cleavage in a highly effective manner. Our results highlighted the crucial significance of Ser422 phosphorylation and suggest that the kinase associated with this Ser-phosphorylation may protect Tau from aggregation. Thus specific promoters/activators of this kinase may find useful therapeutic benefits in arresting Tau truncation by caspase-3 and the progression of AD. In addition our data demonstrated that Tau-peptides where Ser422 or Asp421 are substituted by their respective dextro isomers, exhibit different cleavage kinetics by caspase-3 and this may have important implications in therapeutic intervention of Tau aggregation and associated AD.

Post-Translational Protein Modifications of Rare and Unconventional Types: Implications in Functions and Diseases.

Protein post-translational modification (PTM) occurs following their biosynthesis and is a key cellular event that defines their ultimate functional properties. It is an important control mechanism for display of biological functions of proteins often in a profound manner. It may switch on or off a protein's function. Several studies have been conducted to understand their mechanisms, physiological pathways and functional properties. PTMs have been shown to alter structural, conformational and physicochemical properties of proteins. So far a variety of protein modifications have been detected in physiological systems. These involve covalent modifications of amino acids via their side chains, backbone peptide bonds and terminal moieties. Following PTM, proteins may become (a) pathologically toxic, (b) biologically active or inactive, (c) more or less susceptible to proteolytic processing, (d) increasingly/decreasingly bound to its partner protein/s, or (e) modified with altered protease activities. These changes may affect pathways linked to cell signaling/transduction, trafficking, storing, expression, binding and/or affinity. Any of these events may be linked to metabolic, growth and/or chronic dysfunctions with serious health consequences that may include cancer, cardiovascular disease, stroke, viral/bacterial/parasite infections, inflammation, thrombosis, diabetes; central nervous system related conditions. Some of the modifications are more prevalent physiologically and widely studied. However, in recent years additional PTMs have been described that are less common. These include glypiation, neddylayion, siderophorylation, sumoylation, AMPylation, Cholesteroylation and others which are also important. This manuscript provides a comprehensive review of these rare and unconventional types of protein modifications and their functional implications to health, metabolism and disease conditions.

LDL-R promoting activity of peptides derived from human PCSK9 catalytic domain (153-421): design, synthesis and biochemical evaluation.

BACKGROUND: High level of Low Density Lipoprotein-Cholesterol (LDL-C) in circulation in the blood is associated with an elevated risk of cardiovascular disease (CVD) and stroke. Currently the statin drugs which inhibit the enzyme HMG-CoA reductase responsible for cholesterol synthesis in the liver are very effective in lowering LDL-cholesterol. However these drugs are often associated with serious side effects particularly for ∼10-12% of cases. Therefore there is a need to develop non-statin based cholesterol reducing agents. Recently it was revealed that the secreted Proprotein Convertase Subtilisin Kexin 9 (PCSK9) binds with LDL-receptor (LDL-R) causing its degradation in the lysosome with the result of LDL-C accumulating in the blood. Thus PCSK9 has become an alternative target for development of non-statin cholesterol reducing agents. It is established that the catalytic domain of PCSK9 (aa153-421) and the EGF-A domain of LDL-R (aa314-355) are involved in the above bind leading to the reduction of LDL-R level and accumulation of LDL-C. OBJECTIVE: The major goal of this study is to identify peptide/s from the catalytic domain of hPCSK9 that can block the binding of hPCSK9 and LDL-R and therefore can reduce LDL-R degradation leading to the clearance of LDL-C from the plasma. RESULTS: Using 51 synthetic linear peptides (P1-P51) of 15aa long with 10 amino acids overlapping sequences spanning the entire catalytic segment of hPCSK9 (aa153-421), we identified two domains of hPCSK9 namely (aa323-358) and (aa365-384) that exhibited strong binding affinity towards synthetic EGF-A peptide. The results were based on mass spectrometry, fluorescence spectroscopy and native gel electrophoresis. Thus peptides containing the above segments in part (P35-P39 and P42-P47) exhibited LDL-R promoting activity when added exogenously to culture medium of growing human hepatic cells like HepG2 and HuH7. The effects were particularly significant with peptides P36, P37, P46 and P47. Interestingly, the first two peptides are present within the disulphide loop Cys(323)-Cys(358) and contain the key gain of function mutation D(374)/Y site while the last two peptides contain another disulphide bridge loop Cys(375)-Cys(378) and the second most potent gain of function mutation R(357)/H. Further studies revealed that S-S bridged cyclic loop peptide hPCSK9(365-384) exhibited the highest (∼3.5-fold) LDL-R promoting activity in both HepG2 and HuH7 when applied at 5 µM concentration level. This effect is completely abrogated when one of the Cys residues is substituted by Ala thereby preventing any S-S bond formation. This suggested its critical role in the bioactivity. It is proposed that LDL-R promoting activity of this and other selected PCSK9 catalytic peptides such as P36, P37, P46 and P47 are most likely mediated via intervention of PCSK9:LDL-R complex formation. Our findings may find useful application in future development of small molecule PCSK9 inhibitors for intervention of hypercholesterolemia and associated cardiovascular disease.