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Scholarly Works (32 results)

  • Thesis
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UC Riverside Electronic Theses and Dissertations (2013)

Cadherins play pivotal roles in the toxicity of Bacillus thuringiensis Cry proteins. Here I tested and showed that an Aedes cadherin (AAEL007478) and an N-cadherin (AAEL000597) are involved in the in vivo toxicity of Cry11A toxin to Aedes aegypti. Aedes cadherin was stably expressed in a mosquito cell line and these cells showed increased sensitivity (37% death) to Cry11Aa toxin. These results show Aedes cadherin mediates Cry11Aa toxicity, but since high toxicity was not obtained, an additional secondary receptor may be needed for manifestation of full toxicity. Using a whole genome screen to identify genes that are altered during Cry11Aa intoxication, I identified an N-cadherin gene (AAEL000597) that was significantly down-regulated. An EGF-LamG fragment from this N-cadherin bound Cry11Aa with high affinity and competed with Cry11Aa binding to mosquito midgut membranes. Moreover, N-cadherin-silenced mosquitoes showed tolerance to Cry11Aa, implying that this cadherin is involved in mediating Cry11Aa toxicity. I also showed that this N-cadherin interacts with an amino acid on loop α-8 of Cry11Aa, which is different from that which interacts with the Aedes cadherin binding region. These data suggest that Cry11Aa probably has two different pathogenic pathways that act through two different cadherins in Ae. aegypti.

I also established a Cry11A-resistant strain to determine which mode of action is involved in Aedes Cry11Aa resistance. Brush border membranes from this strain (G30) bound Cry11Aa less compared to the binding in the wild type (WT), implying Cry11Aa resistance results from altered receptor binding affinity, but not proteolytic activity since no change in the latter was observed. Using RNA-seq analyses, immunoblot assays and mass spectrometry, we found the N-cadherin (AAEL000597) and an alkaline phosphatase (ALP, AAEL003298) were down-regulated in Cry11A-resistant larvae midgut. These results strongly suggest that N-cadherin and ALP are associated with Cry11Aa resistance in Ae. aegypti.

In summary, based on data in the literature and my work, I demonstrate that two different pathways of Cry11Aa toxicity are possible; one involving an N-cadherin and the other a combination of Aedes cadherin and an ALP in Ae. aegypti. Moreover, N-cadherin and ALP not only mediate Cry11Aa toxicity, but they were appear to be associated with Cry11Aa resistance. ALP has been proposed as a secondary receptor mediating Cry11Aa toxicity with Aedes cadherin, and hence attenuation of its expression can lead to Cry11A resistance.

    Cover page: Toxin Binding Receptors and the Mode of Action of Bacillus thuringiensis subsp. israelensis Cry Toxins
    • Article
    • Peer Reviewed
    UC Riverside Previously Published Works (2014)
    Bacillus thuringiensis subsp. israelensis (Bti) is widely used for the biological control of mosquito populations. However, the mechanism of Bti toxins is still not fully understood. To further elucidate the mechanism of Bti toxins, we developed an Aedes aegypti resistant strain that shows high-level resistance to Cry11Aa toxin. After 27 selections with Cry11Aa toxin, the larvae showed a 124-fold resistance ratio for Cry11Aa (strain G30). G30 larvae showed cross-resistance to Cry4Aa (66-fold resistance), less to Cry4Ba (13-fold), but not to Cry11Ba (2-fold). Midguts from these resistant larvae did not show detectable difference in the processing of the Cry11Aa toxin compared to that in susceptible larvae (WT). Brush border membrane vesicles (BBMV) from resistant larvae bound slightly less Cry11Aa compared to WT BBMV. To identify potential proteins associated with Cry11A resistance, not only transcript changes in the larval midgut were analyzed using Illumina sequencing and qPCR, but alterations of previously identified receptor proteins were investigated using immunoblots. The transcripts of 375 genes were significantly increased and those of 208 genes were down regulated in the resistant larvae midgut compared to the WT. None of the transcripts for previously identified receptors of Cry11Aa (Aedes cadherin, ALP1, APN1, and APN2) were altered in these analyses. The genes for the identified functional receptors in resistant larvae midgut did not contain any mutation in their sequences nor was there any change in their transcript expression levels compared to WT. However, ALP proteins were expressed at reduced levels (∼ 40%) in the resistant strain BBMV. APN proteins and their activity were also slightly reduced in resistance strain. The transcript levels of ALPs (AAEL013330 and AAEL015070) and APNs (AAEL008158, AAEL008162) were significantly reduced. These results strongly suggest that ALPs and APNs could be associated with Cry11Aa resistance in Ae. aegypti.
      Cover page: Alkaline phosphatases and aminopeptidases are altered in a Cry11Aa resistant strain of Aedes aegypti
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2024)
      BACKGROUND: Statins reduce the risk of cardiovascular events in patients with chronic kidney disease (CKD). Although diabetes mellitus (DM) is a reported side effect of statin treatment, some studies have indicated that pitavastatin does not cause DM. The present study investigated the effect of pitavastatin on the fatty acid (FA) content of erythrocyte membranes, which affects the occurrence of DM and cardiovascular diseases. In addition, changes in adiponectin and glycated hemoglobin (HbA1c) levels were evaluated after pitavastatin treatment. METHODS: A total of 45 patients were enrolled, 28 of whom completed the study. Over 24 weeks, 16 patients received 2 mg pitavastatin and 12 patients received 10 mg atorvastatin. Dosages were adjusted after 12 weeks if additional lipid control was required. There were 10 and nine patients with DM in the pitavastatin and atorvastatin groups, respectively. Erythrocyte membrane FAs and adiponectin levels were measured using gas chromatography and enzyme-linked immunosorbent assay, respectively. RESULTS: In both groups, saturated FAs, palmitic acid, trans-oleic acid, total cholesterol, and low-density lipoprotein cholesterol levels were significantly lower than those at baseline. The arachidonic acid (AA) content in the erythrocyte membrane increased significantly in the pitavastatin group, but adiponectin levels were unaffected. HbA1c levels decreased in patients treated with pitavastatin. No adverse effects were associated with statin treatment. CONCLUSION: Pitavastatin treatment in patients with CKD may improve glucose metabolism by altering erythrocyte membrane AA levels. In addition, pitavastatin did not adversely affect glucose control in patients with CKD and DM.
        Cover page: Effect of pitavastatin on erythrocyte membrane fatty acid content in patients with chronic kidney disease: two-arm parallel randomized controlled trial.
        • Article
        • Peer Reviewed
        UC Irvine Previously Published Works (2021)
        BACKGROUND: Statin treatment has decreased the risk of cardiovascular events in patients with chronic kidney disease (CKD). Erythrocyte membrane oleic acid level is higher in patients with acute coronary syndrome. This study aimed to evaluate the effect of pravastatin on the erythrocyte membrane fatty acid (FA) contents in patients with CKD. METHODS: Sixty-two patients were enrolled from January 2017 to March 2019 (NCT02992548). Pravastatin was initially administered at a dose of 20 mg for 24 weeks. The pravastatin dose was increased to 40 mg after 12 weeks if it was necessary to control dyslipidemia. The primary outcome was change in erythrocyte membrane FA, including oleic acid, after pravastatin treatment for 24 weeks. RESULTS: Forty-five patients finished this study, and there was no adverse effect related to pravastatin. Compared with baseline, total cholesterol and low-density lipoprotein cholesterol levels were significantly decreased after pravastatin treatment. Compared with baseline, saturated FA, oleic acid, and arachidonic acid levels were significantly increased and polyunsaturated FA and linoleic acid (LA) levels were significantly decreased after pravastatin treatment. There was also a decrease in eicosapentaenoic acid after pravastatin treatment in CKD patients with estimated glomerular filtration rate <60 mL/min/1.73 m2. CONCLUSION: Administration of pravastatin in patients with CKD leads to a decrease in FA known to be protective against the risk of CVD. Omega-3 FA or LA supplementation might be necessary to recover changes in erythrocyte membrane FA contents when pravastatin is used for treating dyslipidemia in patients with CKD.
          Cover page: Effect of pravastatin on erythrocyte membrane fatty acid contents in patients with chronic kidney disease.
          • Article
          • Peer Reviewed
          UC Irvine Previously Published Works (2021)
          Mitochondrial dysfunction contributes to the pathogenesis of kidney injury related with cardiovascular disease. Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) protects renal tubular cells by upregulating nuclear factor erythroid 2-related factor 2 (Nrf2). AMP-activated protein kinase (pAMPK)-mediated phosphorylation and sirtuin 1/3 (SIRT1/3)-mediated deacetylation are required for PGC-1α activation. In the present study, we aimed to investigate whether omega-3 fatty acids (FAs) regulate the expression of mediators of mitochondrial biogenesis in 5/6 nephrectomy (Nx) rats. Male Sprague-Dawley rats were assigned to the following groups: sham control, Nx, and Nx treated with omega-3 FA. The expression of PGC-1α, phosphorylated PGC-1α (pPGC-1α), acetylated PGC-1α, and factors related to mitochondrial biogenesis was examined through Western blot analysis. Compared to the control group, the expression of PGC-1α, pAMPK, SIRT1/3, Nrf1, mTOR, and Nrf2 was significantly downregulated, and that of Keap 1, acetylated PGC-1α, and FoxO1/3, was significantly upregulated in the Nx group. These changes in protein expression were rescued in the omega-3 FA group. However, the expression of pPGC-1α was similar among the three groups. Omega-3 FAs may involve mitochondrial biogenesis by upregulating Nrf1 and Nrf2. This protective mechanism might be attributed to the increased expression and deacetylation of PGC-1α, which was triggered by SIRT1/3.
            Cover page: Omega-3 Fatty Acids Upregulate SIRT1/3, Activate PGC-1α via Deacetylation, and Induce Nrf1 Production in 5/6 Nephrectomy Rat Model.
            • Article
            • Peer Reviewed
            UC Irvine Previously Published Works (2022)
            Serum myostatin and indoxyl sulfate (IS) levels increase with kidney function decline and may function as uremic toxins in chronic kidney disease (CKD)-related sarcopenia. Herein, we analyzed the association between serum myostatin and IS levels and sarcopenia in patients with CKD, by performing a post hoc analysis of baseline data extracted from the RECOVERY study (clinicaltrials.gov: NCT03788252) of 150 patients with CKD. We stratified patients into two groups according to the median value of myostatin (cutoff 4.5 ng/mL) and IS levels (cutoff 0.365 mg/dL). The proportion of patients with sarcopenia was higher in those with high IS levels but lower in those with high myostatin levels. The skeletal muscle mass index (SMI) and handgrip strength (HGS) were significantly lower in patients with high IS levels but significantly higher in patients with high myostatin levels. IS levels showed a negative correlation with glomerular filtration rate (GFR), SMI, and HGS. However, myostatin levels were positively correlated with SMI and HGS, but not with GFR. Sarcopenia was independently associated with age and IS level after adjustment. Increased levels of serum total IS might play a role in sarcopenia, while increased levels of serum myostatin are associated with muscle mass in patients with CKD.
              Cover page: Indoxyl Sulfate Might Play a Role in Sarcopenia, While Myostatin Is an Indicator of Muscle Mass in Patients with Chronic Kidney Disease: Analysis from the RECOVERY Study.
              • Article
              • Peer Reviewed
              UC Irvine Previously Published Works (2019)
              BACKGROUND: Serum myostatin levels are increased according to renal function decline and myostatin may be a main mediator of chronic kidney disease-related sarcopenia. A previous study reported that serum myostatin level was negatively associated with abdominal aortic calcification (AAC) in older males. The aim of this study was to assess the association between serum myostatin level and AAC among dialysis patients of both sexes. In addition, we analyzed the relationship between serum myostatin level, muscle mass, and bone mineral density (BMD). METHODS: In this cross-sectional study, we evaluated AAC in the lateral lumbar spine using plain radiography and BMD in 71 patients undergoing dialysis. We classified patients into two groups according to the median value of myostatin as follows: those with high myostatin levels (≥ 5.0 ng/mL) and those with low myostatin levels (< 5.0 ng/mL). RESULTS: The proportion of patients with an AAC score of five points or more was higher among those with low myostatin levels. Myostatin level was negatively associated with AAC scores on plain radiography and had a positive association with skeletal muscle mass and T-scores for BMD measured at the total hip and femur neck. Lower myostatin levels were independently associated with higher AAC scores following adjustment for age, sex, diabetes mellitus, dialysis vintage, dialysis modality, and osteoprotegerin level. CONCLUSION: Lower serum myostatin levels were associated with higher AAC scores, lower muscle mass, and lower BMD in dialysis patients. Further, prospective studies and those with larger cohorts are necessary to validate these findings.
                Cover page: Serum myostatin levels are associated with abdominal aortic calcification in dialysis patients.
                • Article
                • Peer Reviewed
                UC Riverside Previously Published Works (2015)
                Cadherin plays an important role in the toxicity of Bacillus thuringiensis Cry proteins. We previously cloned a full-length cadherin from Aedes aegypti larvae and reported this protein binds Cry11Aa toxin from B. thuringiensis subsp. israelensis with high affinity, ≈16.7nM. Based on these results, we investigated if Aedes cadherin is involved in the in vivo toxicity of Cry11Aa toxin to Ae. aegypti. We established a mosquito cell line stably expressing the full-length Aedes cadherin and transgenic mosquitoes with silenced Aedes cadherin expression. Cells expressing the Aedes cadherin showed increased sensitivity to Cry11Aa toxin. Cry11Aa toxin at 400nM killed approximately 37% of the cells in 3h. Otherwise, transgenic mosquitoes with silenced Aedes cadherin expression showed increased tolerance to Cry11Aa toxin. Furthermore, cells expressing Aedes cadherin triggered Cry11Aa oligomerization. These results show the Aedes cadherin plays a pivotal role in Cry11Aa toxicity to Ae. aegypti larvae by mediating Cry11Aa oligomerization. However, since high toxicity was not obtained in cadherin-expressing cells, an additional receptor may be needed for manifestation of full toxicity. Moreover, cells expressing Aedes cadherin were sensitive to Cry4Aa and Cry11Ba, but not Cry4Ba. However transgenic mosquitoes with silenced Aedes cadherin expression showed no tolerance to Cry4Aa, Cry4Ba, and Cry11Ba toxins. These results suggest that while Aedes cadherin may mediate Cry4Aa and Cry11Ba toxicity, this cadherin but is not the main receptor of Cry4Aa, Cry4Ba and Cry11Ba toxin in Ae. aegypti.
                  Cover page: Aedes cadherin mediates the in vivo toxicity of the Cry11Aa toxin to Aedes aegypti
                  • Article
                  • Peer Reviewed
                  UC Davis Previously Published Works (2022)

                  Introduction

                  Optimal management of pediatric perforated appendicitis remains a topic of active investigation. Our institutional clinical practice guidelines (CPGs) were modified to discontinue antibiotics on discharge for patients with normal white blood cell count (WBC) without left shift. We hypothesized that patients would receive fewer antibiotics without increased complications.

                  Methods

                  Patients <18 y old with perforated appendicitis who underwent laparoscopic appendectomy between November 1, 2016 and May 31, 2021 at a tertiary care children's hospital were included. Primary outcome was adverse events: postdischarge surgical site infection (SSI), 30-day emergency department (ED) visits, or readmissions. Outcomes were compared before and after CPG modification. Multivariable regression was performed to identify factors associated with SSI.

                  Results

                  There were 113 patients pre- and 97 patients post-CPG modification. 23.1% of patients in the pre-cohort had an elevated discharge WBC or left shift compared to 18.9% of patients in the post-cohort (P = 0.48). Significantly fewer patients were prescribed antibiotics on discharge in the post-cohort (70.8% pre versus 14.4% post, P < 0.0001) and for fewer days (2 pre versus 0 post, P < 0.0001). Total antibiotic days decreased significantly (6.1 pre versus 4.6 post, P < 0.0001). There was an increase in postdischarge SSIs on univariate analysis (1.8% pre versus 9.3% post, P = 0.03), ED visits (9.7% pre versus 19.6% post, P = 0.04), and readmissions (5.3% pre versus 11.3% post, P = 0.13). On multivariable analysis, being in the post-cohort was not significantly associated with post-discharge SSIs after adjusting for sex, symptom duration, initial WBC, and discharge antibiotic duration (OR 0.25, 95% CI 0.04-1.4, P = 0.11).

                  Conclusions

                  Modification of a pediatric perforated appendicitis clinical practice guideline to discontinue antibiotics on discharge with a normal WBC without left shift was effective in decreasing antibiotic duration. This was associated with an increase in SSIs on univariate analysis, which did not persist on multivariable analysis and requires further investigation.
                    Cover page: The Utility of Discharge Antibiotics in Pediatric Perforated Appendicitis Without Leukocytosis
                    • Article
                    • Peer Reviewed
                    UC Irvine Previously Published Works (2024)
                    Mitochondrial homeostasis is controlled by biogenesis, dynamics, and mitophagy. Mitochondrial dysfunction plays a central role in cardiovascular and renal disease and omega-3 fatty acids (FAs) are beneficial for cardiovascular disease. We investigated whether omega-3 fatty acids (FAs) regulate mitochondrial biogenesis, dynamics, and mitophagy in the kidney and heart of adenine-induced uremic rats. Eighteen male Sprague Dawley rats were divided into normal control, adenine control, and adenine with omega-3 FA groups. Using Western blot analysis, the kidney and heart expression of mitochondrial homeostasis-related molecules, including peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α), dynamin-related protein 1 (Drp1), and phosphatase and tensin homolog-induced putative kinase 1 (PINK1) were investigated. Compared to normal, serum creatinine and heart weight/body weight in adenine control were increased and slightly improved in the omega-3 FA group. Compared to the normal controls, the expression of PGC-1α and PINK1 in the kidney and heart of the adenine group was downregulated, which was reversed after omega-3 FA supplementation. Drp1 was upregulated in the kidney but downregulated in the heart in the adenine group. Drp1 expression in the heart recovered in the omega-3 FA group. Mitochondrial DNA (mtDNA) was decreased in the kidney and heart of the adenine control group but the mtDNA of the heart was recovered in the omega-3 FA group. Drp1, which is related to mitochondrial fission, may function oppositely in the uremic kidney and heart. Omega-3 FAs may be beneficial for mitochondrial homeostasis by activating mitochondrial biogenesis and PINK1-dependent mitophagy in the kidney and heart of uremic rats.
                      Cover page: Omega-3 Fatty Acids Modify Drp1 Expression and Activate the PINK1-Dependent Mitophagy Pathway in the Kidney and Heart of Adenine-Induced Uremic Rats.
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