Biology subjects

Caldwell, R. W.

Publications and source records attributed to Caldwell, R. W..

3 recordsLinked to original sources

bioRxiv2026

PEG-Arginase 1: A Novel Therapy for Optic Nerve Injury

Traumatic optic neuropathy (TON) occurs due to direct or indirect injury to the optic nerve and is a significant cause of visual disability. So far, there is no effective treatment. The lack of understanding of the cellular mechanisms by which trauma induces inflammation and damage in retinal neurons is a critical knowledge gap in developing effective therapies. We have studied the role of the arginase 1 (A1) enzyme in this pathology. We have found previously that treatment with a long-acting form of human recombinant A1, pegylated A1 (PEG-A1) after optic nerve crush limits activation of retinal microglia and macrophages (M{Phi}) and reduces inflammation, thereby decreasing injury and protecting visual function. Here we report on studies designed to demonstrate the therapeutic efficacy of PEG-A1 in mouse models of direct and indirect TON and to elucidate the underlying mechanisms. We used ONC to model direct TON and sonication-induced trauma to the supraorbital rim to model indirect TON (SI-TON). At different times after injury, mice were treated with PEG-A1 which was delivered systemically by i.p. injection or locally by intravitreal injection. In order to assess the role of A1-induced activation of the ornithine/polyamine pathway in the protective effects of PEG-A1, some mice were treated with the ornithine decarboxylase (ODC) inhibitor, difluoromethylornithine (DFMO) immediately after the PEG-A1 treatment. Retinal function was determined by OptoMotry and electroretinography. Retinal injury and microglia/M{Phi} activation were assessed by immunofluorescence imaging. Expression of inflammatory cytokines was determined by Western blotting and quantitative RT PCR. Liquid chromatography mass spectrometry was used to analyze changes in arginase/ODC pathway metabolites. Results showed that PEG-A1 treatment improved neuronal survival and visual function whether delivered systemically or intravitreally. This neuroprotection was associated with decreased microglia/M{Phi} activation, decreased inflammatory cytokine expression, and increased formation of L-ornithine and putrescine. Furthermore, DFMO treatment blocked these effects, indicating that PEG-A1 limits retinal injury and preserves vision after ocular injury by activating ODC. ODC processes the arginase product L-ornithine to form polyamines which are known to promote reparative functions. Thus, PEG-A1 therapy offers a new strategy to limit trauma-induced vision loss and promote repair after TON.

cell biology↗

bioRxiv2025

Novel Role of AcylCoA:cholesterol acyltransferase 1 (ACAT1/SOAT1) in Diabetic Retinopathy

Hypercholesterolemia and excessive cholesterol ester (CE) production have been linked to chronic inflammation and vascular dysfunction during cardiovascular disease. Upregulation of AcylCoA:cholesterol acyltransferase 1 (ACAT1/SOAT1), the enzyme responsible for retinal CE formation, has been implicated in pathological retinal neovascularization. Here we determine the role of this process in diabetic retinopathy (DR). Ins2Akita diabetic mice were treated with the specific ACAT1/SOAT1 inhibitor K604 (10 mg/Kg, i.p.) beginning at 10 weeks for 2 weeks or 8 months for 2 months. ACAT1/SOAT1 expression and CE formation were assayed along with oxidative stress, inflammation, vascular pathology, and neuronal function. ACAT1/SOAT1 expression was also assayed in human retinas and vitrectomy specimens. Retinas from early-stage Ins2Akita mice exhibited increases in CE deposition, superoxide production, and expression of ACAT1/SOAT1, LDLR, TREM1, MCSF, and VEGF along with leukostasis, vascular leakage, acellular capillary formation, retinal ganglion cell loss, and impaired visual function. Late-stage increases in CE, ACAT1/SOAT, oxidative stress, inflammation, and impaired visual function were also observed. These changes were significantly inhibited by K604 treatment. The protective effects were independent of changes in systemic glucose or body weight. Human retina and vitrectomy samples also showed increases in ACAT1/SOAT1 and CE, respectively. Specific inhibition of ACAT1/SOAT1 with K604 normalizes ACAT1/SOAT1 expression and CE formation and prevents increases in oxidative stress and inflammation and preserves retinal structure and function in both early and late stages of DR. These findings identify ACAT1/SOAT1 as a promising therapeutic target for both early intervention and later stage treatment of DR. One sentence summaryInhibiting cholesterol esterification limits retinal neurovascular injury in diabetes.

cell biology↗

bioRxiv2022

The LncRNA Carmn is a Critical Regulator for Gastrointestinal Smooth Muscle Contractile Function and Motility

Background & aimsVisceral smooth muscle cells (SMCs) are an integral component of the gastrointestinal (GI) tract and are critical for regulating motility. SMC contraction is regulated by changes in post-translational signaling and the state of differentiation. Impaired SMC contraction is associated with significant morbidity and mortality but the mechanisms regulating the expression levels of SMC-specific contractile proteins, including the role of long non-coding RNAs (lncRNAs), remains largely unexplored. Herein, we have uncovered an important role of Carmn (Cardiac mesoderm enhancer-associated noncoding RNA), a SMC-specific lncRNA, in regulating the phenotype of visceral SMCs of the GI tract. MethodsAnalysis of GTEx and publicly available single-cell RNA sequencing (scRNA-seq) datasets from embryonic, adult human and mouse GI tissues were used to identify SMC-specific lncRNAs. The functional role of Carmn was investigated using a novel GFP knock-in (KI) reporter/knockout (KO) mouse model. Bulk RNA sequencing (RNA-seq) and single nuclei RNA sequencing (snRNA-seq) of colonic muscularis were used to investigate underlying mechanisms. ResultsUnbiased in silico analyses and GFP expression patterns in Carmn GFP KI mice revealed that Carmn is specifically expressed in SMCs in human and mouse GI tract. Premature lethality was observed in global Carmn KO (gKO) and inducible SMC-specific KO (iKO) mice due to colonic pseudo-obstruction, severe distension of the GI tract with blockages in cecum and colon segments. Histology, whole-gut GI transit time and muscle myography analysis revealed severe dilation, significantly delayed GI transit and impaired GI contractility in Carmn KO mice versus control mice. Bulk RNA-seq of colonic muscularis revealed that Carmn deficiency promotes SMC de-differentiation as evidenced by up-regulation of extracellular matrix genes and down-regulation of SMC contractile genes including Mylk, a key regulator of SMC contraction. SnRNA-seq further revealed SMC Carmn deficiency not only compromised myogenic motility by reducing expression of contractile genes but also impaired neurogenic motility by disrupting cell-cell connectivity in the colonic muscularis. These findings may have translational significance as silencing CARMN in human colonic SMCs significantly attenuated contractile gene expression including MYLK and decreased SMC contractility. Luciferase reporter assays showed that CARMN enhances the transactivation activity of the master regulator of SMC contractile phenotype, myocardin, thereby maintaining the GI SMC myogenic program. ConclusionOur data suggest that Carmn is indispensable for maintaining GI SMC contractile function in mice, and that loss of function of CARMN may contribute to human visceral myopathy. To our knowledge this is the first study showing an essential role of lncRNA in the regulation of visceral SMC phenotype.

cell biology↗