Fibrosing colonopathy associated with cysteamine bitartrate delayed-release capsules in cystinosis patients.

BACKGROUND: The objective of this report is to identify and characterize cases of fibrosing colonopathy, a rare and underrecognized adverse event, associated with cysteamine delayed-release (DR) in patients with nephropathic cystinosis. METHODS: We searched the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) and the medical literature for postmarketing reports of fibrosing colonopathy associated with cysteamine through August 2, 2023. RESULTS: We identified four cases of fibrosing colonopathy reported with the use of cysteamine DR. The time to onset ranged from 12 to 31 months. In one case, the patient required surgery to have a resection of a section of the strictured colon and a diverting ileostomy. Fibrosing colonopathy was diagnosed by histopathology in two of the cases. CONCLUSIONS: Our case series identified the risk of fibrosing colonopathy in patients taking cysteamine DR and prompted regulatory action by the FDA. As outlined in changes to the U.S. prescribing information for cysteamine DR, healthcare professionals should be aware of the potential risk of fibrosing colonopathy with cysteamine DR, especially as symptoms can be non-specific leading to misdiagnosis or delayed diagnosis. If the diagnosis of fibrosing colonopathy is confirmed, consideration should be given to permanently discontinuing cysteamine DR and switching to cysteamine immediate-release treatment.

Juvenile Bone Toxicity: Study Considerations, Regulations, and Techniques for Assessment.

Recommendations on study designs that adequately evaluate the in-life effects leading to juvenile bone toxicity, the various imaging modalities that can aid interpretation of the bone effects, biomarkers that may be useful, and regulatory issues were presented in this 2020 ACT symposium. The pathologies encountered in past studies were briefly mentioned. The first speaker covered study design and the numbers of juveniles that may be necessary to power the evaluation. Changes in the International Council for Harmonisation (IHC) guidelines were reviewed. The second speaker launched the rest of the symposium by describing the tools that may help assess juvenile bone toxicity, specifically those used to monitor bone toxicity, healing, and remodeling as they relate or drive the study design including model, species selection, and age. The third speaker addressed in more depth the micro-Computed Tomography (CT) applications in juvenile toxicology for evaluation of skeletal elements and bone growth in both embryo-fetal development (EFD) and pre and postnatal development (PPND) studies. Lastly, a regulatory perspective on strategies to assess juvenile bone toxicity and the concerns of the regulatory agency with respect to these potential changes in the juvenile population was addressed.

Mechanisms of skeletal muscle injury and repair revealed by gene expression studies in mouse models.

Common acute injuries to skeletal muscle can lead to significant pain and disability. The current therapeutic approaches for treating muscle injuries are dependent on the clinical severity but not on the type of injury. In the present studies, the pathophysiology and molecular pathways associated with two different types of skeletal muscle injury, one induced by direct destruction of muscle tissue (i.e. FI) and the other induced by a contractile overload (more specifically high-force eccentric contractions, i.e. CI) were compared side by side. Histopathological evaluation and measurements of muscle strength were accompanied by analyses of expression for 12 488 known genes at four time points ranging from 6 h to 7 days after injury. Real-time RT-PCR was used to confirm some of the injury type differences in the temporal profiles of gene expression. Our data revealed several pools of genes, including early induction of transcription, myogenic and stress-responsive factors, common for both types of injury as well as pools of genes expressed specifically with one of the injury types. Only CI activated a set of genes associated with the repair of impaired proteins and structures including genes related to apoptosis, whereas FI uniquely activated gene sets involved in extensive inflammatory responses, tissue remodelling, angiogenesis and myofibre/extracellular matrix synthesis. In conclusion, knowledge of the sets of genes associated specifically with the nature of the injury may have application for development of new strategies for acceleration of the recovery process in injured skeletal muscle.

Macrophages and skeletal muscle regeneration: a clodronate-containing liposome depletion study.

The study evaluates the influence of monocytes/macrophages in the mechanisms of skeletal muscle injury using a mouse model and selective depletion of peripheral monocyte with systemic injections of liposomal clodronate (dichloromethylene bisphosphonate). This pharmacological treatment has been demonstrated to induce specific apoptotic death in monocytes and phagocytic macrophages. In the current studies, the liposomal clodronate injections resulted in a marked attenuation of the peak inflammatory response in the freeze-injured muscle in the first three days after injury. The effect was accompanied by a transient reduction (at day 1 or 3 postinjury) of the expression of several genes coding for inflammatory, as well as growth-related mediators, including TNF, monocyte chemoattractant protein (MCP)-1, thioredoxin, high-mobility group AT-hook 1, insulin-like growth factor-binding protein (IGFBP), and IGF-1. In contrast, the expression of major myogenic factors (i.e., MyoD and myogenin) directly involved in the activation/proliferation and differentiation of muscle precursor cells was not altered by the clodronate liposome treatment. The repair process in the injured muscle of clodronate liposome-treated mice was characterized by prolonged clearance of necrotic myofibers and a tendency for increased muscle fat accumulation at day 9 and 14 postinjury, respectively. In conclusion, a significant reduction of the initial monocyte/macrophage influx into the injured muscle is associated with not improved, but moderately impaired, repair processes after skeletal muscle injury.

Role of CC chemokines in skeletal muscle functional restoration after injury.

The purpose of this study was to determine whether certain chemokines, which are highly expressed in injured skeletal muscle, are involved in the repair and functional recovery of the muscle after traumatic injury. In wild-type control mice, mRNA transcripts of macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and monocyte chemoattractant protein (MCP)-1 as well as their major receptors, CCR5 and CCR2, increased after freeze injury and gradually returned to control (uninjured) levels by 14 days. Muscle function and histological characteristics were monitored in injured mice that were genetically deficient for the CCR5 receptor (a major receptor for MIP-1alpha and MIP-1beta) and also rendered MCP-1 deficient with neutralizing antibodies. To dissect the role of these chemokines, additional studies were conducted in CCR5- and CCR2-deficient mice. CCR5-/- mice injected with MCP-1 antiserum for the first 3 days after injury exhibited a twofold greater maximal isometric tetanic torque deficit at 14 days after injury than did controls (i.e., 33% vs. 17%; P = 0.002). The impaired functional recovery was accompanied with an increased fat infiltration within the regenerating muscle without a significant difference in the influx of inflammatory cells, including macrophages. Strength recovery was also impaired in mice deficient for the receptor of MCP-1, CCR2, but not in CCR5-/- mice that were not injected with MCP-1 antiserum. The data suggest that MCP-1/CCR2 plays a role in the regeneration and recovery of function after traumatic muscle injury.

Inflammatory mediators and skeletal muscle injury: a DNA microarray analysis.

Traumatic skeletal muscle injury causes a specific sequence of cellular events consisting of degeneration, inflammation, regeneration, and fibrosis. The role of early posttraumatic mechanisms, including acute inflammatory response, in muscle repair is not well understood. In the present study, oligonucleotide microarray analyses were used to examine the candidate genes that are involved in these early events of the muscle injury/repair process. cDNA was prepared from the injured and control tibialis anterior (TA) muscle of mice 24 h postinjury and labeled with the fluorescent dye Cy5 or Cy3 prior to hybridization to a DNA microarray. The microarray analysis, including 732 genes, was conducted in triplicate, and we describe only genes modulated by the injury showing a differential expression (both increased and decreased) 1.7-fold or greater (p < 0.05) from control uninjured TA muscle. Selected expression patterns were confirmed by other gene expression detection methods, including real-time reverse transcription-polymerase chain reaction (RT-PCR) and RNase protection assay (RPA) or immunohistochemistry detection methods. The upregulated genes (2.8%) were mainly associated with inflammation, oxidative stress, and cell proliferation, whereas the downregulated genes (3.2%) were related to metabolic and cell signaling pathways. In addition, the study suggested that chemokines, such as monocyte chemoattractant protein-1 (MCP-1), associated with monocyte/macrophage influx and activation, are abundantly expressed in postinjured muscle, and they might play a role in traumatic muscle injury/recovery processes.

Novel non-labile covalent binding of sulfamethoxazole reactive metabolites to cultured human lymphoid cells.

Sulfamethoxazole (SMX) causes rare hypersensitivity syndrome reactions characterized by fever and multi-organ toxicity. Covalent binding of SMX reactive metabolites to cellular proteins has been demonstrated but the link between cytotoxicity and targets of covalent binding has not been explored. We therefore investigated the relationship between covalent binding of the reactive SMX-hydroxylamine (SMX-HA) metabolite, and its cytotoxicity to a hystiocytic lymphoma (U937) cell line. Incubation of U937 cells with 0-1 mM SMX-HA for 3 h resulted in dose-dependent cytotoxicity, as assessed by tetrazolium dye conversion at 24 h. SMX-HA caused dose-dependent covalent binding to cellular proteins as assessed by immunoblotting with SMX antisera at 3 and 24 h. Covalent binding was predominantly to proteins of approximately 45, 59 and 75 kDa, but other targets were also observed. The relative extent of binding to proteins was significantly different from the relative cytotoxicity at 24 h. Further, cells surviving at 24 h also had extensive covalent binding. Covalent binding was observed under reducing (beta-mercaptoethanol) and non-reducing conditions to plasma membrane and microsomal but not cytosolic proteins. This non-labile covalent binding has not been previously reported. These observations suggest that extensive covalent binding does not necessarily lead to cell death, allowing the accumulation of potentially immunogenic drug-protein conjugates. These observations in whole cells may be relevant to the immunopathogenesis of SMX hypersensitivity syndrome reactions.

A simple mathematical model to aid quantification of electrophoresis gels by image analysis.

In many scientific disciplines, measurements are taken from films that have been exposed to energetic sources. Examples include radiographs where the source is an X-ray tube, autoradiography where the source is a radioactive isotope and electrophoresis gels where the source is an enhanced chemiluminescence reaction. In these situations it is of interest to quantify the darkening of the film and compute the strength of the source which in the cases of autoradiography and electrophoresis can be used to compute unknown concentrations of biochemicals. We developed a simple mathematical model of the darkening of films in radiography, autoradiography and electrophoresis bands disclosed by enhanced chemiluminescence, and present formulae to calculate the strength of the source from measurement of film blackening by image analysis. A simple model is used in two examples to predict blackening of film exposed to electromagnetic radiation. This blackening is measured by image analysis. Results show reasonable agreement between predictions of the model and blackening of film for the examples chosen. This model is proposed as an aid to quantification of electrophoresis gels.