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Open Access Publications from the University of California

Scholarly Works (10 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2024)

Trauma/hemorrhagic shock (T/HS) continues to be the most common cause of potentially preventable deaths worldwide, characterized by severe blood loss, hypotension, and inadequate tissue perfusion. Achieving hemodynamic stabilization and effective resuscitation in fulminant shock remains challenging due to the scarcity and cost of blood and blood products, compounded by patients often becoming refractory to fluid reperfusion and vasopressor therapy. The lack of an established optimal treatment regimen stems from an incomplete understanding of shock pathophysiology, particularly the mechanisms within the vasculature. This dissertation aims to address this knowledge gap by investigating the roles of two key determinants of arterial hemodynamics – arterial resistance and arterial compliance – in experimental T/HS. Our studies demonstrate that severe T/HS leads to cardiovascular autonomic failure, endothelial dysfunction, vascular hyporeactivity in resistance arteries, and reduced α1-adrenergic receptor (α1AR) density in vascular smooth muscle cells. We identified a novel mechanism whereby the desensitization of α1ARs is associated with the activation of the toll-like receptor 4 (TLR4) via co-internalization, suggesting a link between the NF-κB inflammatory pathway and vascular hyporesponsiveness in resistance arteries. Evaluation of large artery compliance following T/HS revealed biomechanical impairment, along with changes in material stiffness, residual wall stress, and extracellular matrix structure/composition. In vivo assessment of arterial compliance using pulse wave velocity showed a strong correlation with final blood pressure values at the end of the T/HS experiment. A significant elevation in serine protease and matrix metalloproteinase activity in both circulating plasma and aortic tissue were observed as well. Enteral administration of a broad-spectrum serine protease inhibitor, gabexate mesilate, was used an adjunctive treatment to crystalloid reperfusion in our T/HS model to combat the potential destruction caused by pancreatic proteases leaking from the intestine, which becomes ischemic and permeable upon shock. Gabexate mesilate proved efficacious in mitigating adverse effects in both resistance and conduit arteries, by preserving α1AR surface availability and vasopressor responsiveness in arterioles, while also partially maintaining large arterial structure and elasticity, and ultimately improving hemodynamic stability. Our findings indicate the potential deleterious impact of circulating gut-derived proteases on vascular function in T/HS and underscores the need for more targeted therapies aimed at protecting or restoring the structure and function of both small resistance and large compliance arteries in circulatory shock.

    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2022)
    The standard of care for fluid resuscitation of trauma/hemorrhagic shock (T/HS) is the infusion of blood. However, in many instances, blood product transfusion may not be feasible. Consequently, crystalloid solutions may be utilized as temporizing cost-effective resuscitation fluids. In this study, we explored an alternative therapeutic strategy of enteral protease inhibition adjunctive to intravenous Lactated Ringer's (LR) reperfusion after T/HS. Male Wistar rats underwent midline laparotomy (trauma) and an enteral catheter was inserted orally and positioned post-pyloric for the infusion of vehicle (Golytely®) with or without the serine protease inhibitor gabexate mesilate (GM) (n=8/group). Hemorrhagic shock was induced by blood removal to reduce the mean arterial blood pressure (MAP) to 35-40 mmHg for 90 minutes, before resuscitation with LR. Animals treated with enteral GM required significantly less crystalloid volume to achieve hemodynamic stability and displayed improvements in both blood pressure and autonomic function (via increased baroreflex sensitivity to vasopressors, heightened vascular sympathetic modulation, elevated levels of circulating catecholamines, and increased α1-adrenergic receptor density) compared to untreated (control) shocked animals. Resistance arteries isolated from healthy donor animals and perfused with plasma from untreated T/HS animals revealed impaired vascular response to the α1 adrenergic agonist phenylephrine and decreased reactivity to sodium nitroprusside that was preserved in the GM-treated group. These findings suggest that blockade of serine proteases within the intestinal lumen in non-blood resuscitated experimental T/HS preserves and enhances peripheral sympathetic modulation, improving hemodynamics. Enteral infusion of gabexate mesilate may be a new and promising approach to the management of trauma/hemorrhagic shock.
      Cover page: Enteral gabexate mesilate improves volume requirements and autonomic cardiovascular function after experimental trauma/hemorrhagic shock in the absence of blood reperfusion.
      • Article
      • Peer Reviewed
      UC San Diego Previously Published Works (2021)
      Refractory vascular failure due to the inability of vascular smooth muscle to respond to vasoconstrictors such as phenylephrine is a final common pathway for severe circulatory shock of any cause, including trauma/hemorrhagic shock. Increased inflammation, Toll-like receptor 4 activation, and decreased response of the alpha-1 adrenergic receptors which control vascular tone have been reported in trauma/hemorrhagic shock.

      Hypothesis

      In trauma/hemorrhagic shock, Toll-like receptor 4 activation contributes to vascular failure via decreased bioavailability of adrenergic receptors.

      Design and measurements

      Trauma/hemorrhagic shock was induced in Wistar rats (laparotomy combined with mean arterial pressure at 40 mm Hg for 90 min followed by 2 hr resuscitation with Lactated Ringers solution). To inhibit Toll-like receptor 4, resatorvid (TAK-242) and resveratrol were used, and plasma was collected. Smooth muscle cells were incubated with lipopolysaccharide (10 ng/mL) or plasma. Inflammatory cytokines were screened using dot-blot. Toll-like receptor 4 and nuclear factor κB activation and cellular localization of the alpha-1 adrenergic receptor were measured by immunofluorescence imaging and Western blot analysis. Clustered regularly interspaced short palindromic repeats/Cas9 was used to knock out Toll-like receptor 4, and calcium influx following stimulation with phenylephrine was recorded.

      Main results

      Trauma/hemorrhagic shock caused a decreased response to phenylephrine, whereas Toll-like receptor 4 inhibition improved blood pressure. Trauma/hemorrhagic shock plasma activated the Toll-like receptor 4/nuclear factor κB pathway in smooth muscle cells. Double labeling of Toll-like receptor 4 and the alpha-1 adrenergic receptor showed that these receptors are colocalized on the cell membrane. Activation of Toll-like receptor 4 caused cointernalization of both receptors. Calcium influx was impaired in cells incubated with trauma/hemorrhagic shock plasma but restored when Toll-like receptor 4 was knocked out or inhibited.

      Conclusions

      Activation of the Toll-like receptor 4 desensitizes vascular smooth muscle cells to vasopressors in experimental trauma/hemorrhagic shock by reducing the levels of membrane alpha-1 adrenergic receptor.
        Cover page: Involvement of Toll-Like Receptor 4 in Decreased Vasopressor Response Following Trauma/Hemorrhagic Shock
        • Article
        • Peer Reviewed
        UC San Diego Previously Published Works (2023)
        Preserving vascular function is crucial for preventing multiorgan failure and death in ischemic and low-pressure states such as trauma/hemorrhagic shock (T/HS). It has recently been reported that inhibiting circulating proteases released from the bowel to the circulation during T/HS may preserve vascular function and improve outcomes following T/HS. This study aimed to evaluate the role of the serine protease inhibitor gabexate mesilate (GM) in preserving vascular function during T/HS when given enterally. We studied the vascular reactivity of mesenteric arteries from male Wistar rats treated with enteral GM (10 mg/kg) (GM-treated, n = 6) or control (Shock-control, n = 6) following (T/HS) using pressure myography. Concentration-response curves of endothelial-dependent and endothelial-independent agonists (e.g., acetylcholine, sodium nitroprusside) ranging from 10-10 to 10-5 M were performed. In a second set of experiments, ex-vivo arteries from healthy rats were perfused with plasma from shocked animals from both groups and vascular performance was similarly measured. Arteries from the GM-treated group demonstrated a preserved concentration-response curve to the α1 adrenergic agonist phenylephrine compared to arteries from Shock-control animals (- logEC50: - 5.73 ± 0.25 vs. - 6.48 ± 0.2, Shock-control vs. GM-treated, p = 0.04). When perfused with plasma from GM-treated rats, healthy arteries exhibited an even greater constriction and sensitivity to phenylephrine (- logEC50: - 6.62 ± 0.21 vs. - 7.13 ± 0.21, Shock-control vs. GM-treated, p = 0.02). Enteral GM also preserved the endothelium-dependent vascular response to agonists following T/HS and limited syndecan-1 shedding as a marker of glycocalyx compromise (41.84 ± 9 vs. 17.63 ± 3.97 ng/mL, Shock-control vs. GM-treated, p = 0.02). Syndecan-1 cleavage was correlated with plasma trypsin-like activity (r2 = 0.9611). Enteral gabexate mesilate was able to maintain vascular function in experimental T/HS, which was reflected by improved hemodynamics (mean arterial pressure 50.39 ± 7.91 vs. 64.95 ± 3.43 mmHg, Shock-control vs. GM treated, p = 0.0001). Enteral serine protease inhibition may be a potential therapeutic intervention in the treatment of T/HS.
          Cover page: Enteral administration of the protease inhibitor gabexate mesilate preserves vascular function in experimental trauma/hemorrhagic shock
          • Article
          • Peer Reviewed
          UC Irvine Previously Published Works (2024)
          OBJECTIVES: In the United States, pediatric emergency department (ED) visits for behavioral health (BH) are increasing. We sought to determine ED-level characteristics associated with having recommended BH-related policies. METHODS: We conducted a retrospective serial cross-sectional study of National Pediatric Readiness Project assessments administered to US EDs in 2013 and 2021. Changes in responses related to BH items over time were examined. Multivariable logistic regression models examined ED characteristics associated with the presence of specific BH-related policies in 2021. RESULTS: Of 3554 EDs that completed assessments in 2021, 73.0% had BH-related policies, 66.5% had transfer guidelines for children with BH issues, and 38.6% had access to BH resources in a disaster. Of 2570 EDs that completed assessments in both 2013 and 2021, presence of specific BH-related policies increased from 48.6% to 72.0% and presence of appropriate transfer guidelines increased from 56.2% to 64.9%. The adjusted odd ratios (aORs) of having specific BH-related policies were lower in rural (aOR 0.73; 95% confidence interval [CI] 0.57, 0.92) and remote EDs (aOR 0.65; 95% CI 0.48, 0.88) compared to urban EDs; lower among EDs with versus without trauma center designation (aOR 0.80; 95% CI 0.67, 0.95); and higher among EDs with a nurse and physician pediatric emergency care coordinator (PECC) (aOR 1.89; 95% CI 1.54, 2.33) versus those without a PECC. CONCLUSION: Although pediatric readiness for BH conditions increased from 2013 to 2021, gaps remain, particularly among rural EDs and designated trauma centers. Having nurse and physician PECCs is a modifiable strategy to increase ED pediatric readiness pertaining to BH.
            Cover page: Association of emergency department characteristics with presence of recommended pediatric-specific behavioral health policies.
            • Article
            • Peer Reviewed
            UC San Diego Previously Published Works (2017)

            Background

            Irreversible hemorrhagic shock is characterized by hyporesponsiveness to vasopressor and fluid therapy. Little is known, however, about the mechanisms that contribute to this phenomenon. Previous studies have shown that decreased intestinal perfusion in hemorrhagic shock leads to proteolytically mediated increases in gut permeability, with subsequent egress of vasoactive substances systemically. Maintenance of blood pressure is achieved in part by α1 receptor modulation, which may be affected by vasoactive factors; we thus hypothesized that decreases in hemodynamic stability and vasopressor response in shock can be prevented by enteral protease inhibition.

            Methods

            Rats were exposed to experimental hemorrhagic shock (35 mm Hg mean arterial blood pressure for 2 hours, followed by reperfusion for 2 hours) and challenged with phenylephrine (2 μg/kg) at discrete intervals to measure vasopressor responsiveness. A second group of animals received enteral injections with the protease inhibitor tranexamic acid (TXA) (127 mM) along the small intestine and cecum 1 hour after induction of hemorrhagic shock.

            Results

            Blood pressure response (duration and amplitude) to phenylephrine after reperfusion was significantly attenuated in animals subjected to hemorrhagic shock compared with baseline and control nonshocked animals and was restored to near baseline by enteral TXA. Arteries from shocked animals also displayed decreased α1 receptor density with restoration to baseline after enteral TXA treatment. In vitro, rat shock plasma decreased α1 receptor density in smooth muscle cells, which was also abrogated by enteral TXA treatment.

            Conclusion

            Results from this study demonstrate that experimental hemorrhagic shock leads to decreased response to the α1-selective agonist phenylephrine and decreased α1 receptor density via circulating shock factors. These changes are mitigated by enteral TXA with correspondingly improved hemodynamics. Proteolytic inhibition in the lumen of the small intestine improves hemodynamics in hemorrhagic shock, possibly by restoring α1 adrenergic functionality necessary to maintain systemic blood pressure and perfusion.
              Cover page: Enteral tranexamic acid attenuates vasopressor resistance and changes in &agr;1-adrenergic receptor expression in hemorrhagic shock
              • Article
              • Peer Reviewed
              UC San Diego Previously Published Works (2018)
              Obesity and related morbidities pose a major health threat. Obesity is associated with increased blood concentrations of the anorexigenic hormone leptin; however, obese individuals are resistant to its anorexigenic effects. We examined the phenomenon of reduced leptin signaling in a high-fat diet-induced obesity model in mice. Obesity promoted matrix metalloproteinase-2 (Mmp-2) activation in the hypothalamus, which cleaved the leptin receptor's extracellular domain and impaired leptin-mediated signaling. Deletion of Mmp-2 restored leptin receptor expression and reduced circulating leptin concentrations in obese mice. Lentiviral delivery of short hairpin RNA to silence Mmp-2 in the hypothalamus of wild-type mice prevented leptin receptor cleavage and reduced fat accumulation. In contrast, lentiviral delivery of Mmp-2 in the hypothalamus of Mmp-2-/- mice promoted leptin receptor cleavage and higher body weight. In a genetic mouse model of obesity, transduction of cleavage-resistant leptin receptor in the hypothalamus reduced the rate of weight gain compared to uninfected mice or mice infected with the wild-type receptor. Immunofluorescence analysis showed that astrocytes and agouti-related peptide neurons were responsible for Mmp-2 secretion in mice fed a high-fat diet. These results suggest a mechanism for leptin resistance through activation of Mmp-2 and subsequent cleavage of the extracellular domain of the leptin receptor.
                Cover page: Cleavage of the leptin receptor by matrix metalloproteinase–2 promotes leptin resistance and obesity in mice
                • Article
                • Peer Reviewed
                UC San Diego Previously Published Works (2021)
                Traumatic brain injury (TBI) is often accompanied by hemorrhage, and treatment of hemorrhagic shock (HS) after TBI is particularly challenging because the two therapeutic treatment strategies for TBI and HS often conflict. Ischemia/reperfusion injury from HS resuscitation can be exaggerated by TBI-induced loss of autoregulation. In HS resuscitation, the goal is to restore lost blood volume, while in the treatment of TBI the priority is focused on maintenance of adequate cerebral perfusion pressure and avoidance of secondary bleeding. In this study, we investigate the responses to resuscitation from severe HS after TBI in rats, using fresh blood, polymerized human hemoglobin (PolyhHb), and lactated Ringer's (LR). Rats were subjected to TBI by pneumatic controlled cortical impact. Shortly after TBI, HS was induced by blood withdrawal to reduce mean arterial pressure (MAP) to 35-40 mmHg for 90 min before resuscitation. Resuscitation fluids were delivered to restore MAP to ~ 65 mmHg and animals were monitored for 120 min. Increased systolic blood pressure variability (SBPV) confirmed TBI-induced loss of autoregulation. MAP after resuscitation was significantly higher in the blood and PolyhHb groups compared to the LR group. Furthermore, blood and PolyhHb restored diastolic pressure, while this remained depressed for the LR group, indicating a loss of vascular tone. Lactate increased in all groups during HS, and only returned to baseline level in the blood reperfused group. The PolyhHb group possessed lower SBPV compared to LR and blood groups. Finally, sympathetic nervous system (SNS) modulation was higher for the LR group and lower for the PolyhHb group compared to the blood group after reperfusion. In conclusion, our results suggest that PolyhHb could be an alternative to blood for resuscitation from HS after TBI when blood is not available, assuming additional testing demonstrate similar favorable results. PolyhHb restored hemodynamics and oxygen delivery, without the logistical constraints of refrigerated blood.
                  Cover page: Resuscitation from hemorrhagic shock after traumatic brain injury with polymerized hemoglobin
                  • Article
                  • Peer Reviewed
                  UC San Diego Previously Published Works (2023)
                  Introduction: Infection by SARS-CoV-2 and subsequent COVID-19 can cause viral sepsis. We investigated plasma protease activity patterns in COVID-19-induced sepsis with bacterial superinfection, as well as plasma proteomics and peptidomics in order to assess the possible implications of enhanced proteolysis on major protein systems (e.g., coagulation). Methods: Patients (=4) admitted to the intensive care units (ICUs) at the University of California, San Diego (UCSD) Medical Center with confirmed positive test for COVID-19 by real-time reverse transcription polymerase chain reaction (RT-PCR) were enrolled in a study approved by the UCSD Institutional Review Board (IRB# 190699, Protocol #20-0006). Informed consent was obtained for the collection of blood samples and de-identified use of the data. Blood samples were collected at multiple time points and analyzed to quantify a) the circulating proteome and peptidome by mass spectrometry; b) the aminopeptidase activity in plasma; and c) the endopeptidase activity in plasma using fluorogenic substrates that are cleaved by trypsin-like endopeptidases, specific clotting factors and plasmin. The one patient who died was diagnosed with bacterial superinfection on day 7 after beginning of the study. Results: Spikes in protease activity (factor VII, trypsin-like activity), and corresponding increases in the intensity of peptides derived by hydrolysis of plasma proteins, especially of fibrinogen degradation products and downregulation of endogenous protease inhibitors were detected on day 7 for the patient who died. The activity of the analyzed proteases was stable in survivors. Discussion: The combination of multiomics and enzymatic activity quantification enabled to i) hypothesize that elevated proteolysis occurs in COVID-19-induced septic shock with bacterial superinfection, and ii) provide additional insight into malfunctioning protease-mediated systems, such as hemostasis.
                    Cover page: Plasma enzymatic activity, proteomics and peptidomics in COVID-19-induced sepsis: A novel approach for the analysis of hemostasis
                    • Article
                    • Peer Reviewed
                    UC San Francisco Previously Published Works (2023)
                    BACKGROUND: Grade Group 1 (GG1) prostate cancer should be managed with active surveillance (AS). Global uptake of AS remains disappointingly slow and heterogeneous. Removal of cancer labels has been proposed to reduce GG1 overtreatment. We sought to determine the impact of GG1 disease terminology on individuals perceptions and decision making. METHODS: Discrete choice experiments were conducted on 3 cohorts: healthy men, canonical partners (partners), and patients with GG1 (patients). Participants reported preferences in a series of vignettes with 2 scenarios each, permuting key opinion leader-endorsed descriptors: biopsy (adenocarcinoma, acinar neoplasm, prostatic acinar neoplasm of low malignant potential [PAN-LMP], prostatic acinar neoplasm of uncertain malignant potential), disease (cancer, neoplasm, tumor, growth), management decision (treatment, AS), and recurrence risk (6%, 3%, 1%, <1%). Influence on scenario selection were estimated by conditional logit models and marginal rates of substitution. Two additional validation vignettes with scenarios portraying identical descriptors except the management options were embedded into the discrete choice experiments. RESULTS: Across cohorts (194 healthy men, 159 partners, and 159 patients), noncancer labels PAN-LMP or prostatic acinar neoplasm of uncertain malignant potential and neoplasm, tumor, or growth were favored over adenocarcinoma and cancer (P < .01), respectively. Switching adenocarcinoma and cancer labels to PAN-LMP and growth, respectively, increased AS choice by up to 17%: healthy men (15%, 95% confidence interval [CI] = 10% to 20%, from 76% to 91%, P < .001), partners (17%, 95% CI = 12% to 24%, from 65% to 82%, P < .001), and patients (7%, 95% CI = 4% to 12%, from 75% to 82%, P = .063). The main limitation is the theoretical nature of questions perhaps leading to less realistic choices. CONCLUSIONS: Cancer labels negatively affect perceptions and decision making regarding GG1. Relabeling (ie, avoiding word cancer) increases proclivity for AS and would likely improve public health.
                      Cover page: The influence of the cancer label on perceptions and management decisions for low-grade prostate cancer.
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