Vicki Mercado

Mrs. Vicki Mercado

orcid

Research Focus & Metrics

Academic Career Length

10Years (2017-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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31 August 2022 in mSphere
Verified
Journal Article
Open access
JZJacob Zulk
Jacob Zulk
JCJustin R. Clark
Justin R. Clark
SOSamantha Ottinger
Samantha Ottinger
MBMallory B. Ballard
Mallory B. Ballard
MMMarlyd E. Mejia
Marlyd E. Mejia
KPKathryn Patras
Kathryn Patras
UTI is one of the most common causes of outpatient antibiotic use, and rising antibiotic resistance threatens the ability to control UTI unless alternative treatments are developed. Bacteriophage (phage) therapy is gaining renewed interest; however, much like with antibiotics, bacteria can readily become resistant to phages.

28 March 2022 in Systems Biology in Reproductive Medicine
Verified
Journal Article
Closed access
DDDeepa Dongarwar
Deepa Dongarwar
VMVicki Mercado
Vicki Mercado
SASylvia Adu-Gyamfi
Sylvia Adu-Gyamfi
MLMei-Li Laracuente
Mei-Li Laracuente
HSHamisu M. Salihu
Hamisu M. Salihu
With delayed child-bearing age, there has been an increase in infertility rates globally and in the United States (US). Unsurprisingly, there has been a concomitant substantial increase in the number of individuals seeking infertility treatments over the last decade. This study aimed to examine the relationship between race/ethnicity and the utilization of different infertility treatments over the previous decade. We conducted this retrospective cohort study using the United States (US) Birth data files 2011–2019. We calculated the rates of infertility treatment and its subtypes over the study period. Descriptive statistics were utilized to examine the sociodemographic and birth characteristics for overall births and those associated with any infertility treatment and each of its subtypes. We calculated the level of association between race/ethnicity and utilization of infertility treatment and the subtypes using adjusted logistic regression models. We found that the rate of infertility treatments for all subtypes considered, had steadily increased by 63.7% within the past decade. In contrast, fertility enhancing drugs or Intrauterine Insemination (IUI) increased by 134%, and in vitro fertilization (IVF), gamete intrafallopian transfer (GIFT), and zygote intrafallopian transfer (ZIFT) treatments increased by 40% over the 9-year study period. Non-Hispanic (NH) Asian women had the highest rate of any infertility treatment with a rate of 25 per 1000 births whereas Hispanic women had the lowest rate of any infertility treatment at 5.8 per 1000 births. When compared with NH-White women, NH-Asian women had a modest 7% lower likelihood (OR = 0.93, 95% CI = 0.92–0.94) of receiving any infertility treatment while NH-Black and Hispanic women had about 70% lower likelihood of receiving any infertility treatment. Our report of increased assisted reproductive technology (ART) utilization rates, and marked racial/ethnic differences in ART utilization highlight the importance of expanding knowledge of inequities that continue to impact marginalized groups, a critical step for informing actionable strategy formulations (i.e., advocacy, policy change, patient education, provider training) to address these inequities.

1 January 2017 in Cell Stress and Chaperones
Verified
Journal Article
Open access
PDF file
ELEmily C. Lumley
Emily C. Lumley
AOAcadia R. Osborn
Acadia R. Osborn
JSJessica E. Scott
Jessica E. Scott
ASAmanda G. Scholl
Amanda G. Scholl
VMVicki Mercado
Vicki Mercado
JBJay L. Brewster
Jay L. Brewster
The endoplasmic reticulum (ER) has the ability to signal organelle dysfunction via a complex signaling network known as the unfolded protein response (UPR). In this work, hamster fibroblast cells exhibiting moderate levels of ER stress were compared to those exhibiting severe ER stress. Inhibition of N-linked glycosylation was accomplished via a temperature-sensitive mutation in the Dad1 subunit of the oligosaccharyltransferase (OST) complex or by direct inhibition with tunicamycin (Tm). Temperature shift (TS) treatment generated weak activation of ER stress signaling when compared to doses of Tm that are typically used in ER stress studies (500–1000 nM). A dose-response analysis of key ER stress signaling mediators, inositol-requiring enzyme 1 (IRE1) and protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), revealed 20–40 nM of Tm to generate activation intensity similar to TS treatment. In parental BHK21 cells, moderate (20–40 nM) and high doses (200–1000 nM) of Tm were compared to identify physiological and signaling-based differences in stress response. Inhibition of ER Ca2+ release via ITPR activity with 2-aminoethoxydiphenyl borate (2-APB) or Xestospongin C (XeC) was sufficient to protect against apoptosis induced by moderate but not higher doses of Tm. Analysis of kinase activation over a range of Tm exposures revealed the p38 stress-activated protein kinase (SAPK) to display increasing activation with Tm dosage. Interestingly, Tm induced the extracellular regulated kinases (Erk1/2) only at moderate doses of Tm. Inhibition of ER transmembrane stress sensors (IRE1, PERK) or cytosolic signaling mediators (p38, Jnk1, Erk1/2) was used to evaluate pathways involved in apoptosis activation during ER stress. Inhibition of either PERK or p38 was sufficient to reduce cell death and apoptosis induced by moderate, but not high, doses of Tm. During ER stress, cells exhibited a rapid decline in anti-apoptotic Mcl-1 and survivin proteins. Inhibition of PERK was sufficient to block this affect. This work reveals moderate doses of ER stress to generate patterns of stress signaling that are distinct from higher doses and that apoptosis activation at moderate levels of stress are dependent upon PERK and p38 signaling. Studies exploring ER stress signaling should recognize that this signaling acts as a rheostat rather than a simple switch, behaving distinctively in a dose-dependent manner.

9 January 2025 in JCI Insight
Verified
Journal Article
Open access
PDF file
VMVicki Mercado
Vicki Mercado
HBHolly Branthoover
Holly Branthoover
CCClaude Chew
Claude Chew
CSCamille Serchejian
Camille Serchejian
ASAlexander B. Saltzman
Alexander B. Saltzman
KPKathryn Patras
Kathryn Patras
Urinary neutrophils are a hallmark of urinary tract infection (UTI), yet the mechanisms governing their activation, function, and efficacy in controlling infection remain incompletely understood. Tamm-Horsfall glycoprotein (THP), the most abundant protein in urine, uses terminal sialic acids to bind an inhibitory receptor and dampen neutrophil inflammatory responses. We hypothesized that neutrophil modulation is an integral part of THP-mediated host protection. In a UTI model, THP-deficient mice showed elevated urinary tract bacterial burdens, increased neutrophil recruitment, and more severe tissue histopathological changes compared with WT mice. Furthermore, THP-deficient mice displayed impaired urinary NETosis during UTI. To investigate the effect of THP on NETosis, we coupled in vitro fluorescence-based NET assays, proteomic analyses, and standard and imaging flow cytometry with peripheral human neutrophils. We found that THP increases proteins involved in respiratory chain, neutrophil granules, and chromatin remodeling pathways; enhances NETosis in an ROS-dependent manner; and drives NET-associated morphologic features including nuclear decondensation. These effects were observed only in the presence of a NETosis stimulus and could not be solely replicated with equivalent levels of sialic acid alone. We conclude that THP is a critical regulator of NETosis in the urinary tract, playing a key role in host defense against UTI.

25 November 2020 in Biomedicines
Verified
Journal Article
Open access
PDF file
VMVicki Mercado
Vicki Mercado
DDDeepa Dongarwar
Deepa Dongarwar
KFKristen Fisher
Kristen Fisher
HSHamisu M. Salihu
Hamisu M. Salihu
GHGeorge Joseph Hutton
George Joseph Hutton
FCFenando Cuascut
Fenando Cuascut
Multiple Sclerosis (MS) is a progressive neurodegenerative disease that affects more than 2 million people worldwide. Increasing knowledge about MS in different populations has advanced our understanding of disease epidemiology and variation in the natural history of MS among White and minority populations. In addition to differences in incidence, African American (AA) and Hispanic patients have greater disease burden and disability in earlier stages of disease compared to White patients. To further characterize MS in AA and Hispanic populations, we conducted a retrospective chart analysis of 112 patients treated at an MS center in Houston, Texas. Here, we describe similarities and differences in clinical presentation, MRI findings, treatment regimens, disability progression, and relapse rate. While we found several similarities between the groups regarding mean age, disability severity, and degree of brain atrophy at diagnosis, we also describe a few divergences. Interestingly, we found that patients who were evaluated by a neurologist at symptom onset had significantly decreased odds of greater disability [defined as Expanded Disability Status Scale (EDSS) > 4.5] at last presentation compared to patients who were not evaluated by a neurologist (OR: 0.04, 95% CI: 0.16–0.9). We also found that active smokers had significantly increased odds of greater disability both at diagnosis and at last clinical encounter compared to nonsmokers (OR: 2.44, 95% CI: 1.10–7.10, OR= 2.44, 95% CI: 1.35–6.12, p = 0.01, respectively). Additionally, we observed significant differences in treatment adherence between groups. Assessment of the degree of brain atrophy and progression over time, along with an enumeration of T1, T2, and gadolinium-enhancing brain lesions, did not reveal differences across groups.

9 February 2023 in bioRxiv
Verified
Preprint
Open access
PDF file
MMMarlyd E. Mejia
Marlyd E. Mejia
VMVicki Mercado
Vicki Mercado
JZJacob Zulk
Jacob Zulk
SOSamantha Ottinger
Samantha Ottinger
KRKorinna Ruiz
Korinna Ruiz
KPKathryn Patras
Kathryn Patras
Vaginal microbiota composition is associated with differential risk of urogenital infection. Although vaginal Lactobacillus spp. are thought to confer protection through acidification, bacteriocin production, and immunomodulation, lack of an in vivo model system that closely resembles the human vaginal microbiota remains a prominent barrier to mechanistic discovery. We performed 16S rRNA amplicon sequencing of wildtype C57BL/6J mice, commonly used to study pathogen colonization, and found that the vaginal microbiome composition varies highly both within and between colonies from three distinct vivaria. Because of the strong influence of environmental exposure on vaginal microbiome composition, we assessed whether a humanized microbiota mouse ( HMb mice) would model a more human-like vaginal microbiota. Similar to humans and conventional mice, HMb mice vaginal microbiota clustered into five community state types ( h mCST). Uniquely, HMb mice vaginal communities were frequently dominated by Lactobacilli or Enterobacteriaceae . Compared to genetically-matched conventional mice, HMb mice were less susceptible to uterine ascension by urogenital pathobionts group B Streptococcus (GBS) and Prevotella bivia , but no differences were observed with uropathogenic E. coli . Specifically, vaginal Enterobacteriaceae and Lactobacillus were associated with the absence of uterine GBS. Anti-GBS activity of HMb mice vaginal E. coli and L. murinus isolates, representing Enterobacteriaceae and Lactobacillus respectively, were characterized in vitro and in vivo . Although L. murinus reduced GBS growth in vitro , vaginal pre-inoculation with HMb mouse-derived E. coli , but not L. murinus , conferred protection against vaginal GBS burden. Overall, the HMb mice are an improved model to elucidate the role of endogenous microbes in conferring protection against urogenital pathogens. IMPORTANCE: An altered vaginal microbiota, typically with little to no levels of Lactobacillus , is associated with increased susceptibility to urogenital infections, although mechanisms driving this vulnerability are not fully understood. Despite known inhibitory properties of Lactobacillus against urogenital pathogens, clinical studies with Lactobacillus probiotics have shown mixed success. In this study, we characterize the impact of the vaginal microbiota on urogenital pathogen colonization using a humanized microbiota mouse model that more closely mimics the human vaginal microbiota. We found several vaginal bacterial taxa that correlated with reduced pathogen levels but showed discordant effects in pathogen inhibition between in vitro and in vivo assays. We propose that this humanized microbiota mouse platform is an improved model to describe the role of the vaginal microbiota in protection against urogenital pathogens. Furthermore, this model will be useful in testing efficacy of new probiotic strategies in the complex vaginal environment.