Pharmaceutics and Drug Design Commons^™

Analyzing Functional Interactions Of Designed Peptides By Nmr Spectroscopy, Wonsuk Choi

Pharmaceutical Sciences (MS) Theses

The development of small peptide-based therapeutics can be accelerated by the knowledge of relationships between the peptide structure and its functional interactions. Here, we report the analysis of two groups of synthetic peptides designed for two applications – broad bactericidal action and inhibition of protein-protein interactions in human cells. Novel amphiphilic peptides designed for antibacterial application incorporated arginine as cationic amino acids and non-natural amino acids that have aromatic side chains with similar hydrophobic properties as tryptophan. The interaction of lead cyclic peptides and their linear analogs with a phospholipid bilayer mimicking a bacterial membrane was studied using nuclear magnetic …

Tolfenamic Acid Derivatives: A New Class Of Transcriptional Modulators With Potential Therapeutic Applications For Alzheimer’S Disease And Related Disorders, Juanetta Hill, Karim E. Shalaby, Syed W. Bihaqi, Bothaina H. Alansi, Benjamin Barlock, Keykavous Parang, Richard Thompson, Khalid Ourarhni, Nasser H. Zawia

Pharmacy Faculty Articles and Research

The field of Alzheimer’s disease (AD) has witnessed recent breakthroughs in the development of disease-modifying biologics and diagnostic markers. While immunotherapeutic interventions have provided much-awaited solutions, nucleic acid-based tools represent other avenues of intervention; however, these approaches are costly and invasive, and they have serious side effects. Previously, we have shown in AD animal models that tolfenamic acid (TA) can lower the expression of AD-related genes and their products and subsequently reduce pathological burden and improve cognition. Using TA as a scaffold and the zinc finger domain of SP1 as a pharmacophore, we developed safer and more potent brain-penetrating analogs …

Targeting Breast Cancer: The Familiar, The Emerging, And The Uncharted Territories, Hamidreza Montazeri Aliabadi, Arthur Manda, Riya Sidgal, Co Chung

Pharmacy Faculty Articles and Research

Breast cancer became the most diagnosed cancer in the world in 2020. Chemotherapy is still the leading clinical strategy in breast cancer treatment, followed by hormone therapy (mostly used in hormone receptor-positive types). However, with our ever-expanding knowledge of signaling pathways in cancer biology, new molecular targets are identified for potential novel molecularly targeted drugs in breast cancer treatment. While this has resulted in the approval of a few molecularly targeted drugs by the FDA (including drugs targeting immune checkpoints), a wide array of signaling pathways seem to be still underexplored. Also, while combinatorial treatments have become common practice in …

Cyclic Peptides With Antifungal Properties Derived From Bacteria, Fungi, Plants, And Synthetic Sources, Naiera M. Helmy, Keykavous Parang

Pharmacy Faculty Articles and Research

Fungal infections remain a significant concern for human health. The emergence of microbial resistance, the improper use of antimicrobial drugs, and the need for fewer toxic antifungal treatments in immunocompromised patients have sparked substantial interest in antifungal research. Cyclic peptides, classified as antifungal peptides, have been in development as potential antifungal agents since 1948. In recent years, there has been growing attention from the scientific community to explore cyclic peptides as a promising strategy for combating antifungal infections caused by pathogenic fungi. The identification of antifungal cyclic peptides from various sources has been possible due to the widespread interest in …

A New Method For Investigating Bioequivalence Of Inhaled Formulations: A Pilot Study On Salbutamol, Homa Razaei, Maryam Khoubnasabjafari, Vahid Jouyban-Gharamaleki, Hamed Hamishehkar, Mohammad Reza Afshar Mogaddam, Elaheh Rahimpour, Reza Mehvar, Abolghasem Jouyban

Pharmacy Faculty Articles and Research

Purpose: An efficient, cost-effective and non-invasive test is required to overcome the challenges faced in the process of bioequivalence (BE) studies of various orally inhaled drug formulations. Two different types of pressurized meter dose inhalers (MDI-1 and MDI-2) were used in this study to test the practical applicability of a previously proposed hypothesis on the BE of inhaled salbutamol formulations.

Methods: Salbutamol concentration profiles of the exhaled breath condensate (EBC) samples collected from volunteers receiving two inhaled formulations were compared employing BE criteria. In addition, the aerodynamic particle size distribution of the inhalers was determined by employing next generation impactor. …

Genetic Mutations Of KCa2.3 And KCa3.1 Channels Affect Ca2+ Sensitivity, Razan Orfali

Pharmaceutical Sciences (PhD) Dissertations

The Ca²⁺-activated potassium channels K_Ca channels are a unique family of potassium channels activated by intracellular calcium. K_Ca channels are critical for maintaining K⁺ homeostasis and modulate several physiological processes, from the firing properties of neurons to the control of the transmitter release. The Ca²⁺ sensitivity of these channels allows intracellular Ca²⁺ to regulate the electrical activity of the cell membrane. Increased Ca²⁺ sensitivity of K_Ca channels caused by gain of function mutations (GOF) in the KCNN genes results in a broad spectrum of human channelopathies, including Zimmermann- Laband syndrome (ZLS), …

Virtual And In Vitro Screening Of Natural Products Identifies Indole And Benzene Derivatives As Inhibitors Of Sars-Cov-2 Main Protease (MPro), Dony Ang, Riley Kendall, Hagop S. Atamian

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

The rapid spread of the coronavirus disease 2019 (COVID-19) resulted in serious health, social, and economic consequences. While the development of effective vaccines substantially reduced the severity of symptoms and the associated deaths, we still urgently need effective drugs to further reduce the number of casualties associated with SARS-CoV-2 infections. Machine learning methods both improved and sped up all the different stages of the drug discovery processes by performing complex analyses with enormous datasets. Natural products (NPs) have been used for treating diseases and infections for thousands of years and represent a valuable resource for drug discovery when combined with …

Editorial: Adenylyl Cyclase Isoforms As Potential Drug Targets, Tarsis F. Brust, Rennolds S. Ostrom, Val J. Watts

Pharmacy Faculty Articles and Research

Editorial on the Research Topic Adenylyl cyclase isoforms as potential drug targets

The Development Of A Novel Peptide-Drug Conjugate For Treating Triple-Negative Breast Cancer, Phi-Phung Than

Pharmaceutical Sciences (MS) Theses

Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype with poor prognosis and is difficult to treat. A diagnosis of TNBC means that the three most common types of receptors known to fuel most breast cancer growth–estrogen, progesterone, and HER2– are not present in the cancer tumors. Since the tumor cells lack necessary receptors, common treatments like hormone therapies and targeted HER2 drugs are ineffective. The use of chemotherapies in treating TNBC is an effective option instead. However, chemotherapies are not selective, thus they cause severe side effects such as cardiotoxicity, myelosuppression, alopecia and gastrointestinal problems. A peptide-drug conjugate …

The Glycemic, Cholesterol, And Weight Effects Of L-Carnitine In Diabetes: A Systematic Review And Meta-Analysis Of Randomized Controlled Trials, Jennifer Ko, Eva Y. Wong, Huyentran N. Tran, Rebecca J.C. Tran, Diana X. Cao

Pharmacy Faculty Articles and Research

Introduction

L-carnitine possibly impacts insulin sensitivity and glucose metabolism. However, its therapeutic role in diabetes is poorly understood.

Methods

A systematic review and meta-analysis were conducted using PubMed, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) from inception through June 30, 2021. Included studies evaluated the use of L-carnitine in diabetes on fasting blood glucose (FBG), hemoglobin A1c (HbA1c), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), weight, or body mass index (BMI). Weighted mean difference (WMD) and 95% confidence intervals (CI) were calculated using the DerSimonian and Laird random-effects model.

Results

Seventeen studies …

Effects Of Chronic Cirrhosis Induced By Intraperitoneal Thioacetamide Injection On The Protein Content And Michaelis–Menten Kinetics Of Cytochrome P450 Enzymes In The Rat Liver Microsomes, Devaraj Venkatapura Chandrashekar, Barent N. Dubois, Mamunur Rashid, Reza Mehvar

Pharmacy Faculty Articles and Research

Chronic intraperitoneal injection of thioacetamide (TAA) in rats has been used as an animal model of human cirrhosis to study the effects of the disease on drug metabolism. However, TAA inhibits P450 enzymes directly and independently of cirrhosis. We investigated the effects of chronic cirrhosis in rats, induced by 10 weeks of intraperitoneal TAA, on the P450 enzymes after a 10-day washout period to eliminate TAA. Liver histology and serum biomarkers of hepatic function confirmed cirrhosis in all animals. Microsomal total P450 content, P450 reductase activity and ethoxycoumarin O-deethylase activity, a general marker of P450 activity, were significantly reduced by …

Differential Expression And Activities Of Cytochrome P450 3a In The Rat Brain Microsomes And Mitochondria, Nouf Alshammari, Devaraj Venkatapura Chandrashekar, Mamunur Rashid, Reza Mehvar

Pharmacy Faculty Articles and Research

Midazolam (MDZ), a benzodiazepine derivative, is metabolized to 1′- and 4-hydroxylated metabolites (1′-OH-MDZ and 4-OH-MDZ, respectively) by cytochrome P450 3A (CYP3A). The purpose of this study was to investigate the CYP3A-mediated hydroxylation of MDZ in the rat brain mitochondria (MT). Brain microsomes (MC) and MT fractions were prepared from rats (n = 8) using differential and density gradient centrifugations, and the purity of the fractions was evaluated using VDAC1 and calreticulin as markers of MT and MC, respectively. The formation rates of 1′-OH-MDZ and 4-OH-MDZ in the rat brain MC and MT samples were determined using an LC–MS/MS method …

Perturbation Modeling For Molecular Design Of Protein Tyrosine Kinase Inhibitors Using Unsupervised Machine Learning, Keerthi Krishnan

Computational and Data Sciences (MS) Theses

The field of computational drug discovery and development has grown, with the aid of new computational tools for novel molecule discovery. In specific, generative deep learning models have excelled as tools to aid in navigating the large space of known molecules and in the creation of new molecules. These models are fed various representations of molecules as inputs and learn to perform a variety of things, such as the optimization of these molecules towards a targeted property. Ultimately, these generative learning models allow us to build bridges between chemical and continuous spaces to understand the compromise between invoking small incremental …

Cyclic And Linear Cell-Penetarating Peptides Composed Of Tryptophan (Ww) And Arginine (Rr) Residues As Molecular Transporters, Lois Kim

Pharmaceutical Sciences (MS) Theses

The cell membrane has polar and negative charged characteristics and separates the inside of cells from the outside environment, and only allows small molecules to go into the cell to protect them from toxic substances. However, cell membrane characteristics make it difficult for polar and negatively-charged molecules to interact and penetrate the membrane. The delivery of cell impermeable compounds, such as phosphopeptides and siRNA, across the cell membrane remains a challenge. Previous studies in Dr. Parang’s laboratory have shown that cyclic peptides composed of tryptophan (W) and arginine (R) amino acids [WR]₅ have higher cellular uptake than the corresponding …

Effects Of Nnos Inhibitors On Melanoma-Induced Immunosuppression, Kate Alison Lozada

Pharmaceutical Sciences (MS) Theses

The incidence of cutaneous melanoma (CM) rises despite advances in immunotherapy and targeted therapy. Studies have shown that interferon-gamma (IFN-γ), a pro-tumorigenic cytokine in CM, induces the expression of programmed death-ligand 1 (PD-L1), leading to the escape of melanoma cells from immunosurveillance. Our previous study suggests that neuronal nitric oxide synthase (nNOS)-mediated nitric oxide (NO) signaling is crucial for melanoma progression and forms a mechanistic rationale behind nNOS inhibition as a novel treatment strategy for CM. An additional study demonstrated that IFN-γ interacts with nNOS signaling in melanoma and novel nNOS inhibitors (nNOSi) effectively diminished the induction of PD-L1 post …

Full- Versus Sub-Regional Quantification Of Amyloid-Beta Load On Mouse Brain Sections, Yuu Ohno, Riley Murphy, Matthew Choi, Weijun Ou, Rachita K. Sumbria

Pharmacy Faculty Articles and Research

Extracellular accumulation of amyloid-beta (Aβ) plaques is one of the major pathological hallmarks of Alzheimer's disease (AD), and is the target of the only FDA-approved disease-modifying treatment for AD. Accordingly, the use of transgenic mouse models that overexpress the amyloid precursor protein and thereby accumulate cerebral Aβ plaques are widely used to model human AD in mice. Therefore, immunoassays, including enzyme-linked immunosorbent assay (ELISA) and immunostaining, commonly measure the Aβ load in brain tissues derived from AD transgenic mice. Though the methods for Aβ detection and quantification have been well established and documented, the impact of the size of the …

A Small Peptide Increases Drug Delivery In Human Melanoma Cells, Shirley Tong, Shaban Darwish, Hanieh Hossein Nejad Ariani, Kate Alison Lozada, David Salehi, Maris A. Cinelli, Richard B. Silverman, Kamaljit Kaur, Sun Yang

Pharmacy Faculty Articles and Research

Melanoma is the most fatal type of skin cancer and is notoriously resistant to chemotherapies. The response of melanoma to current treatments is difficult to predict. To combat these challenges, in this study, we utilize a small peptide to increase drug delivery to melanoma cells. A peptide library array was designed and screened using a peptide array-whole cell binding assay, which identified KK-11 as a novel human melanoma-targeting peptide. The peptide and its D-amino acid substituted analogue (VPWxEPAYQrFL or D-aa KK-11) were synthesized via a solid-phase strategy. Further studies using FITC-labeled KK-11 demonstrated dose-dependent uptake in human melanoma cells. D-aa …

Computational Design Of Β-Fluorinated Morphine Derivatives For Ph-Specific Binding, Nayiri Alexander, Makena Augenstein, Matthew Gartner

Student Scholar Symposium Abstracts and Posters

The opioid epidemic impacted over 12 million Americans in 2019. Although they are effective pain-relieving medications, they carry addictive and dangerous side effects. Opioids, like morphine, bind non-selectively in both central and peripheral tissues; however, dangerous side effects result from central activation. Inflamed conditions of injured tissues have a lower pH (pH=6-6.5) environment than healthy central tissue (pH=7.4). We aim to design a morphine derivative that binds selectively within inflamed tissue using computationally-based molecular extension and dissection techniques. Binding to the mu-opioid receptor (MOR) is dependent on protonation of the biochemically active amine group of morphine. Fluorination of a carbon …

Targeting Neuronal Nitric Oxide Synthase (Nnos) For Melanoma Treatment, Shirley Tong

Pharmaceutical Sciences (PhD) Dissertations

Human cutaneous melanoma is the most aggressive form of skin cancer and the incidence rates have continued to increase over the years. Neuronal nitric oxide synthase (nNOS) produces nitric oxide (NO) has been found to be overexpressed in human melanoma and the expression of nNOS is induced by interferon-gamma (IFN-γ). In our studies, nNOS has been implicated in IFN-γ-stimulated melanoma progression and the inhibition of nNOS using novel inhibitors effectively inhibited IFN-γ-stimulated tumor growth in a xenograft mouse model. Programmed death-ligand 1 (PD-L1) is overexpressed in melanoma and plays an important role in suppressing the immune system ^12-14. Our …

Oleyl Conjugated Histidine-Arginine Cell-Penetrating Peptides As Promising Agents For Sirna Delivery, Muhammad Imran Sajid, Dindyal Mandal, Naglaa Salem El-Sayed, Sandeep Lohan, Jonathan Moreno, Rakesh Kumar Tiwari

Pharmacy Faculty Articles and Research

Recent approvals of siRNA-based products motivated the scientific community to explore siRNA as a treatment option for several intractable ailments, especially cancer. The success of approved siRNA therapy requires a suitable and safer drug delivery agent. Herein, we report a series of oleyl conjugated histidine–arginine peptides as a promising nonviral siRNA delivery tool. The conjugated peptides were found to bind with the siRNA at N/P ratio ≥ 2 and demonstrated complete protection for the siRNA from early enzymatic degradation at N/P ratio ≥ 20. Oleyl-conjugated peptide -siRNA complexes were found to be noncytotoxic in breast cancer cells (MCF-7 and MDA-MB-231) …

The Use Of Advanced Spectral Imaging To Reveal Nanoparticle Identity In Biological Samples, Qamar A. Alshammari, Rajasekharreddy Pala, Ayan K. Barui, Saud O. Alshammari, Andromeda M. Nauli, Nir Katzir, Ashraf M. Mohieldin, Surya M. Nauli

Pharmacy Faculty Articles and Research

Nanoparticles (NPs) have been used in drug delivery therapies, medical diagnostic strategies, and as current Covid-19 vaccine carriers. Many microscope-based imaging systems have been introduced to facilitate detection and visualization of NPs. Unfortunately, none can differentiate the core and the shell of NPs. Spectral imaging has been used to distinguish a drug molecule and its metabolite. We have recently integrated this technology to a resolution of 9 nm by using artificial intelligence-driven analyses. Such a resolution allowed us to collect many robust datapoints for each pixel of an image. Our analyses could recognize 45 spectral points within a pixel to …

Biologic Tnf-Α Inhibitors Reduce Microgliosis, Neuronal Loss, And Tau Phosphorylation In A Transgenic Mouse Model Of Tauopathy, Weijun Ou, Joshua Yang, Juste Simanauskaite, Matthew Choi, Demi M. Castellanos, Rudy Chang, Jiahong Sun, Nataraj Jagadeesan, Karen D. Parfitt, David H. Cribbs, Rachita K. Sumbria

Pharmacy Faculty Articles and Research

Background

Tumor necrosis factor-α (TNF-α) plays a central role in Alzheimer’s disease (AD) pathology, making biologic TNF-α inhibitors (TNFIs), including etanercept, viable therapeutics for AD. The protective effects of biologic TNFIs on AD hallmark pathology (Aβ deposition and tau pathology) have been demonstrated. However, the effects of biologic TNFIs on Aβ-independent tau pathology have not been reported. Existing biologic TNFIs do not cross the blood–brain barrier (BBB), therefore we engineered a BBB-penetrating biologic TNFI by fusing the extracellular domain of the type-II human TNF-α receptor (TNFR) to a transferrin receptor antibody (TfRMAb) that ferries the TNFR into the brain via …

Development Of A Bamlanivimab Infusion Process In The Emergency Department For Outpatient Covid-19 Patients, Danny Pham, Sandy Wong, Christina T. Nguyen, Stephen C. Lee, Kimberly J. Won

Pharmacy Faculty Articles and Research

The coronavirus disease 2019 (COVID-19) pandemic has prompted the creation of new therapies to help fight against the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Bamlanivimab is a SARS-CoV-2 monoclonal antibody that is administered as an intravenous infusion to ambulatory patients with mild or moderate COVID-19, but a concern that arose was deciding the optimal location for patients to receive the medication. This report describes the development and implementation of a bamlanivimab infusion center in the emergency department of three hospitals in Orange County, California, shortly after bamlanivimab received emergency use authorization. As a result, a total of 601 …

Computational Design Of Β-Fluorinated Morphine Derivatives For Ph-Specific Binding, Makena Augenstein, Nayiri Alexander, Matthew Gartner

Student Scholar Symposium Abstracts and Posters

Molecular extension and dissection techniques are used to design a morphine derivative that promotes selective binding in inflamed tissue due to its lower pH while avoiding dangerous activation in the brain. Morphine is used to treat pain associated with inflammation. While being effective analgesics, opioids carry the risk of central side effects, including addiction, respiratory depression, and sedation. Opioids are agonists that bind to the μ-opioid peptide receptor (MOR) within central and peripheral nerves and act via a G-protein coupled receptor pathway.

Deprotonation of the tertiary amine induces a negative charge on the nitrogen, discouraging binding at physiological pH (pH=7.4). …

The Concentration Of Brain Homogenates With The Amicon Ultra Centrifugal Filters, Joshua Yang, Rachita K. Sumbria

Pharmacy Faculty Articles and Research

Accurately measuring the brain concentration of a neurotherapeutic is critical in determining its pharmacokinetic profile in vivo. Biologics are potential therapeutics for neurologic diseases and biologics fused to an antibody targeting a transcytosis receptor at the Blood-Brain Barrier, designated as antibody-biologic fusion proteins, are Blood-Brain Barrier penetrating neurotherapeutics. The use of sandwich immunosorbent assays to measure concentrations of antibody-biologic fusion proteins in brain homogenates has become increasingly popular. The raw brain homogenate contains many proteins and other macromolecules that can cause a matrix effect, potentially interfering with the limit of detection of such assays and reduce the overall sample …

Uplc-Ms/Ms Analysis Of The Michaelis-Menten Kinetics Of Cyp3a-Mediated Midazolam 1′- And 4-Hydroxylation In Rat Brain Microsomes, Devaraj Venkatapura Chandrashekar, Barent Dubois, Reza Mehvar

Pharmacy Faculty Articles and Research

Midazolam (MDZ) is a short-acting benzodiazepine with rapid onset of action, which is metabolized by CYP3A isoenzymes to two hydroxylated metabolites, 1′-hydroxymidazolam and 4-hydroxymidazolam. The drug is also commonly used as a marker of CYP3A activity in the liver microsomes. However, the kinetics of CYP3A-mediated hydroxylation of MDZ in the brain, which contains much lower CYP content than the liver, have not been reported. In this study, UPLC-MS/MS and metabolic incubation methods were developed and validated for simultaneous measurement of low concentrations of both hydroxylated metabolites of MDZ in brain microsomes. Different concentrations of MDZ (1–500 µM) were incubated with …

Design, Synthesis, And Evaluation Of A Novel Cytotoxic Peptide-Doxorubicin Conjugate Targeting Triple-Negative Breast Cancer, Elmira Ziaei

Pharmaceutical Sciences (PhD) Dissertations

The aim of this thesis was to design, synthesize, and characterize a novel peptide-doxorubicin conjugate, evaluate in vitro stability and cytotoxicity properties of the conjugate and study its mechanism for uptake into the triple-negative breast cancer (TNBC) cells. For the synthesis of the conjugate, first, doxorubicin (Dox) was conjugated to a highly efficient established cross-linker, MCC, to give an intermediate product, MCC-Dox. MCC-Dox was characterized using NMR spectroscopy, mass spectrometry, and RP-HPLC and purified for subsequent reaction. Second, the 11-mer peptide 18-4 (NH₂-CWxEAAYQrFL-CONH₂) with high proteolytic stability and specificity for breast cancer cells was reacted with …

Modulation Of Antibacterial Activity And Cytotoxicity In Amphipathic Cyclic Peptide [R4w4] Using Histidine Substitution, Ryan Stueber

Pharmaceutical Sciences (MS) Theses

Antibiotics have been the gold standard frontline defense against bacterial infections for decades. At the same time, these infecting bacteria have continued to evolve to resist developed antibiotics in an almost endless cycle. As such, we aim to take an alternative approach utilizing antimicrobial peptides (AMPs) as a means to end this cycle. [R4W4] is among known AMPs that demonstrated antimicrobial activity against methicillin-resistant staphylococcus aureus (MRSA) with a minimum inhibitory concentration (MIC) of 2.67 μg/mL. This peptide had notably effective antimicrobial activity, especially relative to linear (R4W4). However, it displayed a concerning level of cytotoxicity; eliciting a human embryonic …

Differential Effect Of Proinflammatory Cytokines On Corneal And Conjunctival Epithelial Cell Mucins And Glycocalyx, Kiumars Shamloo, Priya Mistry, Ashley Barbarino, Christopher Ross, Vishal Jhanji

Pharmacy Faculty Articles and Research

Purpose: Ocular surface mucins and glycocalyx are critical for providing ocular hydration as well lubrication and repelling pathogens or allergens. Elevated levels of tear proinflammatory cytokines in dry eye may have detrimental effect on mucins and glycocalyx. The present study tested the effect of proinflammatory cytokines IL-6, TNF-α, and IFN-γ on membrane-tethered mucins expression, glycocalyx, and viability of ocular surface epithelial cells.

Methods: Stratified cultures of human corneal and conjunctival epithelial cells were exposed to different concentrations of IL-6, TNF-α, and IFN-γ for 24 hours. The mucins gene and protein expressions were quantified by real-time polymerase chain reaction …

Engineering And Characterization Of Human Β-Defensin-3 And Its Analogues And Microcin J25 Peptides Against Mannheimia Haemolytica And Bovine Neutrophils, Harpreet Dhingra, Kamaljit Kaur, Baljit Singh

Pharmacy Faculty Articles and Research

Mannheimia haemolytica-induced bovine respiratory disease causes loss of millions of dollars to Canadian cattle industry. Current antimicrobials are proving to be ineffective and leave residues in meat. Antimicrobial peptides (AMPs) may be effective against M. haemolytica while minimizing the risk of drug residues. Cationic AMPs can kill bacteria through interactions with the anionic bacterial membrane. Human β-Defensin 3 (HBD3) and microcin J25 (MccJ25) are AMPs with potent activity against many Gram-negative bacteria. We tested the microbicidal activity of wild-type HBD3, three HBD3 peptide analogues (28 amino acid, 20AA, and 10AA) derived from the sequence of natural HBD3, and MccJ25 …