Characterizing the mechanism of action for mRNA therapeutics for the treatment of propionic acidemia, methylmalonic acidemia, and phenylketonuria.

Messenger RNA (mRNA) therapeutics delivered via lipid nanoparticles hold the potential to treat metabolic diseases caused by protein deficiency, including propionic acidemia (PA), methylmalonic acidemia (MMA), and phenylketonuria (PKU). Herein we report results from multiple independent preclinical studies of mRNA-3927 (an investigational treatment for PA), mRNA-3705 (an investigational treatment for MMA), and mRNA-3210 (an investigational treatment for PKU) in murine models of each disease. All 3 mRNA therapeutics exhibited pharmacokinetic/pharmacodynamic (PK/PD) responses in their respective murine model by driving mRNA, protein, and/or protein activity responses, as well as by decreasing levels of the relevant biomarker(s) when compared to control-treated animals. These preclinical data were then used to develop translational PK/PD models, which were scaled allometrically to humans to predict starting doses for first-in-human clinical studies for each disease. The predicted first-in-human doses for mRNA-3927, mRNA-3705, and mRNA-3210 were determined to be 0.3, 0.1, and 0.4 mg/kg, respectively.

Systemic Exposure, Metabolism, and Elimination of [14C]-Labeled Amino Lipid, Lipid 5, after a Single Administration of mRNA Encapsulating Lipid Nanoparticles to Sprague-Dawley Rats.

The emerging therapeutic modality of lipid nanoparticle (LNP)-encapsulated mRNAs has demonstrated promising clinical results when used as vaccines and is currently being tested in formulations for a wide range of targeted chronic disease treatments. These therapeutics are multicomponent assemblages of well-characterized naturally occurring molecules in addition to xenobiotic molecules, whose in vivo distributions are poorly understood. Here, the metabolic outcome and in vivo elimination of heptadecan-9-yl 8-((2-hydroxyethyl) (8-(nonyloxy)-8-oxooctyl)amino)octanoate (Lipid 5), a key xenobiotic amino lipid in LNP formulations, were assessed after intravenous administration of 14C-labeled Lipid 5 to Sprague-Dawley rats. Intact Lipid 5 was predominantly cleared from plasma within 10 hour after dosing, with only small quantities (<1% of 14C dose) of a single diacid metabolite detected after 10 hour. Lipid 5 was rapidly metabolized via ester hydrolysis into aliphatic alcohols and diacidic amino head group moieties, which were further metabolized via ß-oxidation. Overall, >90% of the administered Lipid 5-derived 14C was recovered in urine (65%) and feces (35%), predominantly as oxidative metabolites, within 72 hour after dosing, indicating rapid renal and hepatic elimination. In vitro metabolite identification after incubation with human, nonhuman primate, and rat hepatocytes showed similar metabolites to those found in vivo. No meaningful differences were observed in Lipid 5 metabolism or elimination by sex. In conclusion, Lipid 5, a critical amino lipid component of LNPs for mRNA therapeutic delivery, showed minimal exposure, rapid metabolism, and near-complete elimination of 14C metabolites in rats. SIGNIFICANCE STATEMENT: Heptadecan-9-yl 8-((2-hydroxyethyl) (8-(nonyloxy)-8-oxooctyl)amino)octanoate (Lipid 5) is a key component of lipid nanoparticles used for the delivery of mRNA-based medicines; understanding the rates and routes of its clearance is crucial to assessing its long-term safety in lipid nanoparticle technology. This study conclusively established the rapid metabolism, and near-complete elimination of intravenously administered [14C]Lipid 5 in rats via both liver and kidney as oxidative metabolites derived from ester hydrolysis and subsequent ß-oxidation.

Biodistribution of Lipid 5, mRNA, and Its Translated Protein Following Intravenous Administration of mRNA-Encapsulated Lipid Nanoparticles in Rats.

RNA-based therapeutics and vaccines represent a novel and expanding class of medicines, the success of which depends on the encapsulation and protection of mRNA molecules in lipid nanoparticle (LNP)-based carriers. With the development of mRNA-LNP modalities, which can incorporate xenobiotic constituents, extensive biodistribution analyses are necessary to better understand the factors that influence their in vivo exposure profiles. This study investigated the biodistribution of heptadecan-9-yl 8-((2-hydroxyethyl)(8-(nonyloxy)-8-oxooctyl)amino)octanoate (Lipid 5)-a xenobiotic amino lipid-and its metabolites in male and female pigmented (Long-Evans) and nonpigmented (Sprague Dawley) rats by using quantitative whole-body autoradiography (QWBA) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques. After intravenous injection of Lipid 5-containing LNPs, 14C-containing Lipid 5 ([14C]Lipid 5) and radiolabeled metabolites ([14C]metabolites) were rapidly distributed, with peak concentrations reached within 1 hour in most tissues. After 10 hours, [14C]Lipid 5 and [14C]metabolites concentrated primarily in the urinary and digestive tracts. By 24 hours, [14C]Lipid 5 and [14C]metabolites were localized almost exclusively in the liver and intestines, with few or no concentrations detected in non-excretory systems, which is suggestive of hepatobiliary and renal clearance. [14C]Lipid 5 and [14C]metabolites were completely cleared within 168 hours (7 days). Biodistribution profiles were similar between QWBA and LC-MS/MS techniques, pigmented and nonpigmented rats, and male and female rats, excluding the reproductive organs. In conclusion, the rapid clearance through known excretory systems, with no evidence of redistribution for Lipid 5 or accumulation of [14C]metabolites, provides confidence for the safe and effective use of Lipid 5-containing LNPs. SIGNIFICANCE STATEMENT: This study demonstrates the rapid, systemic distribution of intact and radiolabeled metabolites of Lipid 5, a xenobiotic amino lipid component of novel mRNA-LNP medicines, and its effective clearance without substantial redistribution after intravenous administration; additionally, findings were consistent between different mRNAs encapsulated within LNPs of similar composition. This study confirms the applicability of current analytical methods for lipid biodistribution analyses, and taken together with appropriate safety studies, supports the continued use of Lipid 5 in mRNA-medicines.

Enhancing the Anti-tumor Potency of a Novel Siglec-15 Antibody by Engineering its Fc-mediated Effector Functions.

Siglec-15, an inhibitory immune checkpoint, is an emerging target in cancer immunotherapy. Blocking the function of Siglec-15 is an excellent strategy for cancer treatment and antibody blockade has been used to target Siglec-15. However, whether Fc-mediated effector functions contribute to the therapeutic effect of antibodies remains unclear. Herein, we generated a monoclonal antibody, 1-15D1, which had a high binding affinity with Siglec-15 and strongly activated T-cell immune response in vitro. Subsequently, the Fc-mediated effector functions of 1-15D1 were explored in a Siglec-15 humanized mouse model, and further improvement in antitumor efficacy was observed in the mouse IgG2a isotype group. Thus, we demonstrate that the antitumor effects of 1-15D1 were mediated via multiple factors. In addition to the T-cell immune response, 2 novel mechanisms were explored, including the internalization of the cell surface Siglec-15 and Fc-mediated effector functions. In conclusion, our studies not only provide a potential agent for the improvement of cancer immunotherapy but also suggest that a specific role of Fc-mediated immune regulation may improve the therapeutic potency of Siglec-15 monoclonal antibody.

Targeting ZDHHC9 potentiates anti-programmed death-ligand 1 immunotherapy of pancreatic cancer by modifying the tumor microenvironment.

Immune checkpoint blockade (ICB) therapy targeting the programmed death 1/programmed death-ligand 1 (PD-1/PD-L1) axis has achieved considerable success in treating a wide range of cancers. However, most patients with pancreatic cancer remain resistant to ICB. Moreover, there is a lack of optimal biomarkers for the prediction of response to this therapy. Palmitoylation is mediated by a family of 23 S-acyltransferases, termed zinc finger Asp-His-His-Cys-type palmitoyltransferases (ZDHHC), which precisely control various cancer-related protein functions and represent promising drug targets for cancer therapy. Here, we revealed that tumor cell-intrinsic ZDHHC9 was overexpressed in pancreatic cancer tissues and associated with impaired anti-tumor immunity. In syngeneic pancreatic tumor models, the knockdown of ZDHHC9 expression suppressed tumor progression and prolonged survival time of mice by modifying the immunosuppressive ('cold') to proinflammatory ('hot') tumor microenvironment. Furthermore, ZDHHC9 deficiency sensitized anti-PD-L1 immunotherapy mainly in a CD8+ T cell dependent manner. Lastly, we employed the ZDHHC9-siRNA nanoparticle system to efficiently silence ZDHHC9 in pancreatic tumors. Collectively, our findings indicate that ZDHHC9 overexpression in pancreatic tumors is a mechanism involved in the inhibition of host anti-tumor immunity and highlight the importance of inactivating ZDHHC9 as an effective immunotherapeutic strategy and booster for anti-PD-L1 therapy against pancreatic cancer.

Bioluminescence imaging of mouse monocyte chemoattractant protein-1 expression in inflammatory processes.

Monocyte chemoattractant protein-1 (MCP-1) plays a crucial role in various inflammatory diseases. To reveal the impact of MCP-1 during diseases and to develop anti-inflammatory agents, we establish a transgenic mouse line. The firefly luciferase gene is incorporated into the mouse genome and driven by the endogenous MCP-1 promoter. A bioluminescence photographing system is applied to monitor luciferase levels in live mice during inflammation, including lipopolysaccharide-induced sepsis, concanavalin A-induced T cell-dependent liver injury, CCl 4-induced acute hepatitis, and liver fibrosis. The results demonstrate that the luciferase signal induced in inflammatory processes is correlated with endogenous MCP-1 expression in mice. Furthermore, the expressions of MCP-1 and the luciferase gene are dramatically inhibited by administration of the anti-inflammatory drug dexamethasone in a septicemia model. Our results suggest that the transgenic MCP-1-Luc mouse is a useful model to study MCP-1 expression in inflammation and disease and to evaluate the efficiency of anti-inflammatory drugs in vivo.

miR-29cb2 promotes angiogenesis and osteogenesis by inhibiting HIF-3α in bone.

Coordination between osteogenesis and angiogenesis is required for bone homeostasis. Here, we show that miR-29cb2 is a bone-specific miRNA and plays critical roles on angiogenesis-osteogenesis coupling during bone remodeling. Mice with deletion of miR-29cb2 exhibit osteopenic phenotypes and osteoblast impairment, accompanied by pronounced decreases in specific H vessels. The decrease in bone miR-29cb2 was associated with pathological ovariectomy stimuli. Mechanistically, hypoxia-inducible factor (HIF)-3α, as a target for miR-29cb2, inhibits HIF-1α activity by competitively bonding with HIF-1ß. Notably, miR-29cb2 in peripheral blood (PB) nearly is undetectable in sham and significantly increases in ovariectomy mice. Further evaluation from osteoporosis patients demonstrates similar signatures. ROC analysis shows miR-29cb2 in PB has higher sensitivity and specificity for diagnosing osteoporosis when compared with four clinical biomarkers. Collectively, these findings reveal that miR-29cb2 is essential for bone remodeling by inhibiting HIF-3α and elevated bone-specific miR-29cb2 in PB, which may be a promising biomarker for bone loss.

A bioluminescence reporter mouse strain for in vivo imaging of CD8+ T cell localization and function.

CD8+ T cells play a critical role during adaptive immune response, which often change locations and expand or contract in numbers under different states. In the past, many attempts to develop CD8+T cells that express luciferase in vivo have involved the use of viral transduction, which has drawbacks of hardly tracked via detection of luciferase signal in untouched natural states. Here, we generate a transgenic mouse model via CRISPR-mediated genome editing, C57BL/6-CD8aem(IRES-AkaLuci-2A-EGFP) knock-in mice(CD8a-Aka mice), as a novel tool for non-invasive imaging of CD8+ T cells, which expressed a highly sensitive luciferase-Akaluciferase. Our study offers a convenient and robust tool for understanding fundamental CD8+ T cell biology in experimental applications and preclinical translational studies.

Partial depletion and repopulation of microglia have different effects in the acute MPTP mouse model of Parkinson's disease.

OBJECTIVES: Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the progressive and selective degeneration of dopaminergic neurons. Microglial activation and neuroinflammation are associated with the pathogenesis of PD. However, the relationship between microglial activation and PD pathology remains to be explored. MATERIALS AND METHODS: An acute regimen of MPTP was administered to adult C57BL/6J mice with normal, much reduced or repopulated microglial population. Damages of the dopaminergic system were comprehensively assessed. Inflammation-related factors were assessed by quantitative PCR and Multiplex immunoassay. Behavioural tests were carried out to evaluate the motor deficits in MPTP-challenged mice. RESULTS: The receptor for colony-stimulating factor 1 inhibitor PLX3397 could effectively deplete microglia in the nigrostriatal pathway of mice via feeding a PLX3397-formulated diet for 21 days. Microglial depletion downregulated both pro-inflammatory and anti-inflammatory molecule expression at baseline and after MPTP administration. At 1d post-MPTP injection, dopaminergic neurons showed a significant reduction in PLX3397-fed mice, but not in control diet (CD)-fed mice. However, partial microglial depletion in mice exerted little effect on MPTP-induced dopaminergic injuries compared with CD mice at later time points. Interestingly, microglial repopulation brought about apparent resistance to MPTP intoxication. CONCLUSIONS: Microglia can inhibit PD development at a very early stage; partial microglial depletion has little effect in terms of the whole process of the disease; and microglial replenishment elicits neuroprotection in PD mice.

miR-29a/b1 Regulates the Luteinizing Hormone Secretion and Affects Mouse Ovulation.

miR-29a/b1 was reportedly involved in the regulation of the reproductive function in female mice, but the underlying molecular mechanisms are not clear. In this study, female mice lacking miR-29a/b1 showed a delay in vaginal opening, irregular estrous cycles, ovulation disorder and subfertility. The level of luteinizing hormone (LH) was significantly lower in plasma but higher in pituitary of mutant mice. However, egg development was normal in mutant mice and the ovulation disorder could be rescued by the superovulation treatment. These results suggested that the LH secretion was impaired in mutant mice. Further studies showed that deficiency of miR-29a/b1 in mice resulted in an abnormal expression of a number of proteins involved in vesicular transport and exocytosis in the pituitary, indicating the mutant mice had insufficient LH secretion. However, the detailed mechanism needs more research.

mRNA therapy restores euglycemia and prevents liver tumors in murine model of glycogen storage disease.

Glycogen Storage Disease 1a (GSD1a) is a rare, inherited metabolic disorder caused by deficiency of glucose 6-phosphatase (G6Pase-α). G6Pase-α is critical for maintaining interprandial euglycemia. GSD1a patients exhibit life-threatening hypoglycemia and long-term liver complications including hepatocellular adenomas (HCAs) and carcinomas (HCCs). There is no treatment for GSD1a and the current standard-of-care for managing hypoglycemia (Glycosade®/modified cornstarch) fails to prevent HCA/HCC risk. Therapeutic modalities such as enzyme replacement therapy and gene therapy are not ideal options for patients due to challenges in drug-delivery, efficacy, and safety. To develop a new treatment for GSD1a capable of addressing both the life-threatening hypoglycemia and HCA/HCC risk, we encapsulated engineered mRNAs encoding human G6Pase-α in lipid nanoparticles. We demonstrate the efficacy and safety of our approach in a preclinical murine model that phenotypically resembles the human condition, thus presenting a potential therapy that could have a significant therapeutic impact on the treatment of GSD1a.

Betaine/GABA transporter-1 (BGT-1) deficiency in mouse prevents acute liver failure in vivo and hepatocytes apoptosis in vitro.

Betaine/γ-aminobutyric acid (GABA) transporter 1 (BGT-1 or Slc6a12) is a transporter for the neurotransmitter GABA and osmolyte betaine. To date, most studies on BGT-1 have focused on its functions in the nervous system and renal osmotic homeostasis. Despite its dominant distribution in the liver, the function of BGT-1 in hepatic physiology or disease remains unknown. Here, we report that BGT-1 was significantly downregulated in patients with liver failure as well as in mice with experimental acute liver failure (ALF). Furthermore, mice deficient in BGT-1 showed significant resistance to ALF compared with wild type (WT) mice, manifesting as improved survival rate, reduced alanine transaminase/aspartate aminotransferase levels, better histopathological symptoms and fewer apoptotic cells in the liver. Similarly, in primary hepatocytes, BGT-1 deficiency or treatment with a BGT-1 inhibitor, NNC 05-2090, attenuated TNF-α mediated apoptosis. In addition, BGT-1 deficiency or dosing with NNC 05-2090 stimulated the expression of the anti-apoptotic gene, c-Met in the liver, suggesting the involvement of c-Met in the function on hepatocytes of BGT-1 apoptosis. Our findings suggest BGT-1 is a promising candidate drug target to prevent and treat hepatocyte apoptosis related diseases, such as ALF.

Pravastatin regulates host foreign-body reaction to polyetheretherketone implants via miR-29ab1-mediated SLIT3 upregulation.

Host rejection to biomaterials can induce uncontrolled foreign-body reactions (FBR), resulting in a dense fibrous encapsulation that blocks mass transport and/or communication between the host and the implant. Adequate angiogenesis between the body and the implant has been implicated as a key regulator for overcoming FBR. Thus, approaches for stimulating neovascularization and/or suppressing FBR are under investigation. In this study, pravastatin (Pra) was loaded onto a 3D network surface of sulfonated polyetheretherketone (SP) to achieve superior local drug effects. The SP loaded with Pra (SP-Pra) promoted angiogenesis and mitigated FBR via miR-29 dependent SLIT3 upregulation in wild-type (WT) mice. miR-29a and miR-29b1 were significantly downregulated in the SP-Pra capsule compared to levels in the SP capsule, while SLIT3 and neovascularization were substantially upregulated in WT mice. However, the above effects presented in the WT mice were not detected in miR-29ab1 knockout mice which was generated by the CRISPR/Cas9 approach. Overall, the results suggest that miR-29 plays a critical role in reducing FBR to these implants by targeting SLIT3. Suppression of FBR by SP-Pra implants offers the potential to improve the performance of current medical devices.

Purinergic P2X7 receptor blockade mitigates alcohol-induced steatohepatitis and intestinal injury by regulating MEK1/2-ERK1/2 signaling and egr-1 activity.

The P2X7 receptor is an ATP-binding cation channel involved in a broad range of inflammatory diseases. However, little is known about the potential role of P2X7R in alcohol-induced steatohepatitis and intestinal injury. In our study, C57BL/6 mice were intraperitoneally injected with P2X7R antagonists Brilliant Blue G and A438079 from the 4th day to the 10th day during the induction of chronic plus binge alcohol feeding model. Our results showed that alcohol feeding induced significant steatohepatitis and liver injury, which were mitigated by P2X7R blockade as evidenced by decreased serum levels of ALT, AST, T-CHO and TG, reduced lipid accumulation, and less inflammation. The increased intestinal inflammatory cytokines production and the prominent intestinal barrier disruption caused by alcohol were also modulated by P2X7R antagonism. Interestingly, alcohol feeding increased the relative abundance of phylum Bacteroidetes while decreased the number of phylum Verrucomicrobia and genus Akkermansia in the cecal content, which were reversed by P2X7R antagonist. Importantly, the improvement of intestinal barrier function and the restoration of partial taxonomic alterations in the gut microbiota might contribute to protect the liver from gut microbiota dysbiosis-induced second hit. Furthermore, P2X7R blockade inhibited MEK1/2-ERK1/2 phosphorylation and egr-1 expression in both liver and intestine from alcohol-fed mice. Collectively, P2X7R blockade mitigates alcohol-induced steatohepatitis and intestinal injury by inhibiting MEK1/2-ERK1/2 signaling and egr-1 expression. These studies strongly suggest that P2X7R blockade may be a promising therapeutic approach for treating alcoholic liver disease.

Tracing the dynamic expression of the Nfκb2 gene during inflammatory processes by in vivo bioluminescence imaging in transgenic mice.

Nfκb2(p52/p100) plays essential roles in many chronic inflammatory diseases. Tracing the dynamic expression of Nfκb2 during different biological processes in vivo can provide valuable clues to understand the biological functions of this gene and develop anti-inflammatory drugs. In this study, B6-Tg(Nfκb2-luc)Mlit transgenic mouse line, a mouse model in which the expression of firefly luciferase gene is under the control of a 14.6-kb mouse Nfκb2 promoter, was generated to monitor the expression of p52/p100 in vivo. Bioluminescence imaging was used for tracking the luciferase signal in living mice in a variety of inflammatory processes, including LPS-induced sepsis and inflammatory bowel disease (IBD). The data of in vivo bioluminescence imaging in this mouse model showed that luciferase activity coincided with the endogenous p52/p100 expression. Moreover, dexamethasone or aspirin, two routine anti-inflammatory drugs, could decrease the high-level expression of luciferase induced by LPS. Overall, our results suggest that the B6-Tg(Nfκb2-luc)Mlit mice represent a valuable reporter mouse model not only to monitor the expression of p52/p100 in physiological or pathological processes but also to evaluate the effects of various anti-inflammatory drug treatments in vivo.

Fate tracing of hepatocytes in mouse liver.

Hepatocytes perform most of the functions of the liver and are considered terminally differentiated cells. Recently, it has been suggested that hepatocytes might have the potential to transdifferentiate or dedifferentiate under physiological or pathological conditions in vivo. Epithelial-mesenchymal transition of hepatocytes in liver fibrosis has also been proposed. However, these findings have not been fully confirmed. In this study, hepatocytes were genetically labelled for cell fate tracing using lacZ via the tamoxifen-induced CreERT/loxP system. After induction with tamoxifen, alb + cells were permanently marked by lacZ expression, and all progeny lacZ + cells were derived from a single source with no interference. We did not observe transdifferentiation or dedifferentiation of hepatocytes into cholangiocytes or hepatic progenitor cells under conditions of liver homeostasis or following a 2/3 partial hepatectomy. Meanwhile, lacZ/OPN-positive cells were observed in livers of 3,5-diethoxycarbonyl-1,4-dihydrocollidine-fed mice, and lacZ/alpha-smooth muscle actin-positive cells were detected in carbon tetrachloride-induced chronic liver injury models. These results suggested that some existing differentiated alb + cells might have the potential of transdifferentiation/dedifferentiation or epithelial-to-mesenchymal transition in vivo in some liver injury models, but the proportion of these alb + cells in liver was very low, and their significance and actual function during the pathological process remains to be elucidated.

Cystathionine γ-Lyase Deficiency Exacerbates CCl4-Induced Acute Hepatitis and Fibrosis in the Mouse Liver.

AIMS: The present study examined the role of cystathionine γ-lyase (CSE) in carbon tetrachloride (CCl4)-induced liver damage. RESULTS: A CSE gene knock-out and luciferase gene knock-in (KI) mouse model was constructed to study the function of CSE and to trace its expression in living status. CCl4 or lipopolysaccharide markedly downregulated CSE expression in the liver of mice. CSE-deficient mice showed increased serum alanine aminotransferase and aspartate aminotransferase levels, and liver damage after CCl4 challenge, whereas albumin and endogenous hydrogen sulfide (H2S) levels decreased significantly. CSE knockout mice showed increased serum homocysteine levels, upregulation of inflammatory cytokines, and increased autophagy and IκB-α degradation in the liver in response to CCl4 treatment. The increase in pro-inflammatory cytokines, including tumor necrosis factor-alpha in CSE-deficient mice after CCl4 challenge, was accompanied by a significant increase in liver tissue hydroxyproline and α-smooth muscle actin and histopathologic changes in the liver. However, H2S donor pretreatment effectively attenuated most of these imbalances. INNOVATION: Here, a CSE knock-out and luciferase KI mouse model was established for the first time to study the transcriptional regulation of CSE expression in real time in a non-invasive manner, providing information on the effects and potential mechanisms of CSE on CCl4-induced liver injury. CONCLUSION: CSE deficiency increases pro-inflammatory cytokines in the liver and exacerbates acute hepatitis and liver fibrosis by reducing H2S production from L-cysteine in the liver. The present data suggest the potential of an H2S donor for the treatment of liver diseases such as toxic hepatitis and fibrosis. Antioxid. Redox Signal. 27, 133-149.

Functional imaging of Rel expression in inflammatory processes using bioluminescence imaging system in transgenic mice.

c-Rel plays important roles in many inflammatory diseases. Revealing the dynamic expression of c-Rel in disease processes in vivo is critical for understanding c-Rel functions and for developing anti-inflammatory drugs. In this paper, a transgenic mouse line, B6-Tg(c-Rel-luc)(Mlit), which incorporated the transgene firefly luciferase driven by a 14.5-kb fragment containing mouse c-Rel gene Rel promoter, was generated to monitor Rel expression in vivo. Luciferase expression could be tracked in living mice by the method of bioluminescence imaging in a variety of inflammatory processes, including LPS induced sepsis and EAE disease model. The luciferase expression in transgenic mice was comparable to the endogenous Rel expression and could be suppressed by administration of anti-inflammatory drug dexamethasone or aspirin. These results indicate that the B6-Tg(c-Rel-luc)(Mlit) mouse is a valuable animal model to study Rel expression in physiological and pathological processes, and the effects of various drug treatments in vivo.

The µ-opioid receptor variant N190K is unresponsive to peptide agonists yet can be rescued by small-molecule drugs.

The µ-opioid receptor (MOR) plays an important role in modulating analgesia, feeding behavior, and a range of autonomic functions. In the current study, we investigated the degree to which 13 naturally occurring missense mutations affect the pharmacological properties of the human MOR. After expression of each receptor in human embryonic kidney 293 cells, signaling (Gα(i/o)-mediated) induced by peptide agonists was assessed using luciferase reporter gene assays. Multiple mutants (S66F, S147C, R260H, R265C, R265H, and S268P) show a significant reduction in agonist potency. At the N190K variant, agonist-mediated signaling was essentially absent. Enzyme-linked immunosorbent assay, microscopic analysis, and radioligand binding assays revealed that this mutant shows markedly reduced cell-surface expression, whereas all other receptor variants were expressed at normal levels. Surface expression of the N190K variant could be increased by incubation with the alkaloid agonist buprenorphine or with either naltrexone or naloxone, structurally related MOR antagonists. We were surprised to find that both putative antagonists, despite being inactive at the wild-type MOR, triggered a concentration-dependent increase in N190K receptor-mediated signaling. In contrast, peptidic ligands failed to promote expression or rescue function of the N190K mutant. Subsequent analysis of the N190K variant in an ethnically diverse cohort identified this isoform in a subgroup of African Americans. Taken together, our studies reveal that the N190K mutation leads to severe functional alterations and, in parallel, changes the response to established MOR ligands. The extent to which this mutation results in physiological abnormalities or affects drug sensitivity in selected populations (e.g., those with chronic pain or addiction) remains to be investigated.