HSP90, a Common Therapeutic Target for Suppressing Skin Injury Caused by Exposure to Chemically Diverse Classes of Blistering Agents

Chronic kidney disease amplifies severe kidney injury and mortality in a mouse model of skin arsenical exposure

In previously published work, we elucidated the role of cutaneous arsenical exposure in promoting acute kidney injury (AKI) in adult healthy mice. Here, we determine whether preexisting chronic kidney disease (CKD) increases the severity of AKI. Following exposure to aristolochic acid (AA) (a nephrotoxic phytochemical in humans), mice manifested classical markers of CKD, including robust interstitial fibrosis and loss in kidney function. Skin challenge with phenylarsine oxide (PAO), a surrogate for warfare arsenicals, led to significantly worse kidney injury, as evidenced by tubulointerstitial fibrosis, glomerulosclerosis, a persistent loss of estimated glomerular filtration rate, and mortality in AA-induced CKD mice compared with mice without CKD. These PAO-challenged CKD mice exhibited enhanced production of serum/urine neutrophil gelatinase-associated lipocalin and a significant rise in serum creatinine along with histological markers of kidney injury, including brush border loss, tubular atrophy, cast formation, glomerular injury, and interstitial inflammatory cell infiltration. Serum cytokines IL-4, IL-6, IFN-γ, IL-12p70, TNF-α, and IL-18 significantly elevated in CKD mice following PAO exposure when compared with animals exposed to PAO alone. Furthermore, we found increased TUNEL-positive tubular cells in the kidneys of CKD mice following PAO exposure, suggesting enhanced PAO-mediated cell death in CKD mice. Mechanistically, we determined that DNA damage-regulated p53 signaling was a major mediator of cellular responses to PAO in CKD mice. In summary, our data demonstrate that CKD significantly increased the severity of AKI following exposure to arsenicals and suggest that human populations with preexisting CKD could be highly susceptible to arsenical-mediated kidney injury and associated morbidity and mortality.NEW & NOTEWORTHY Preexisting chronic kidney disease (CKD) predisposes experimental animals to augmented morbidity and mortality following cutaneous vesicant exposure. The mechanism underlying increased susceptibility to renal injury and associated morbidity involves the DNA damage-regulated p53 signaling pathway.

Common molecular profile of multiple structurally distinct warfare arsenicals in causing cutaneous chemical vesicant injury

Skin exposure to arsenicals such as lewisite and phenylarsine oxide leads to severe cutaneous damage. Here, we characterized the molecular pathogenesis of skin injury caused by additionally structurally distinct warfare arsenicals including diphenylchlorarsine (DPCA), diphenylcyanoarsine (DPCYA), diethylchloroarsine (DECA). Cutaneous exposure to DPCA/DPCYA showed marked increase in skin erythema and edema at 6 and 24 h followed by scar formation at 72 h, while DECA did not produce such visual injuries in mouse skin. Clinical observations showed significant increase in Draize score and skin bi-fold thickness in a time-dependent manner. DPCA or DPCYA-exposed skin histology revealed highly inflamed hypodermal areas with infiltrated immune cells at 6 and 24 h, however, epidermal cell necrosis was seen at 72 h. Significantly high number of macrophage infiltration observed at 6 h, whereas peak neutrophil infiltration occurred at 72 h. Number of micro-blisters also increased. However, these effects were nonsignificant following topical DECA exposure. RT-PCR confirmed augmented inflammatory responses in the skin challenged with both DPCA/DPCYA, which accompanied increased ROS and unfolded protein response (UPR) signaling. DECA also increased ROS with changes in UPR. Disrupted tight (Yap/ZO-1) and adherens (Yap/α-Catenin) junction proteins underlie time-dependent apoptotic cell death of epidermal keratinocytes. Thus, these studies identify arsenicals-manifested signaling pathways similar to those of lewisite.

Enhancing topical delivery of ISRIB: Optimizing cream formulations with chemical enhancers and pH adjustment

Chemical warfare agents, particularly vesicants like lewisite, pose a threat due to their ability to cause skin damage through accidental exposure or deliberate attacks. Lewisite rapidly penetrates the skin, causing inflammation and blistering. This study focuses on developing a cream formulation of a therapeutic agent, called integrated stress response inhibitor (ISRIB), to treat lewisite-induced injuries. Moreover, animal studies demonstrate a molecular target engagement (ISR) and significant efficacy of ISRIB against lewisite-induced cutaneous injury. The goal of this formulation is to enhance the delivery of ISRIB directly to affected skin areas using an oil-in-water cream emulsion system. We investigated various excipients, including oils, surfactants, emollients, and permeation enhancers, to optimize ISRIB's solubility and penetration through the skin. The result of this study indicated that the optimal formulation includes 30 % w/w of N-Methyl-2-pyrrolidone, dimethyl sulfoxide and Azone® at a pH of 5. 5. It delivered the highest amount of ISRIB into the skin, demonstrating highest skin absorption with no detectable systemic exposure. Additionally, characterization of the cream, including texture analysis, emulsion type, and content uniformity, confirmed its' suitability for topical application. These findings suggest that ISRIB cream formulation is a promising approach for the localized treatment of skin injuries caused by lewisite.

Progress and Challenges in Developing Medical Countermeasures for Chemical, Biological, Radiological, and Nuclear Threat Agents

This Commentary delves into the current progress and challenges on ongoing research on medical countermeasures (MCs) for chemical, biologic, radiologic, and nuclear (CBRN) threats. CBRN agents pose a serious risk to human health and safety, with the potential for mass casualties in both military and civilian settings. Chemical threats are toxic compounds that could be used in a terrorist attack, an accidental release, or chemical warfare. They include nerve agents, organophosphates, pulmonary agents, metabolic/cellular agents, vesicants, ocular toxicants, and opioid agents. Developing effective MCs is crucial for mitigating the acute and chronic effects of exposure to CBRN agents. The papers in this special issue of JPET highlights the latest advancements in MC research, showcasing insightful outcomes on experimental models, mechanisms, and translational research on MCs for CBRN threats. They portray several notable contributions, including the development of neurosteroid and combination anticonvulsant therapies for nerve agent poisoning, the exploration of chronic impacts and diagnostic tracers for OP neurotoxicity, the establishment of innovative pediatric OP models, the identification of novel molecules for ocular, pulmonary and vesicant injuries, and the repurposing of existing drugs for the treatment of botulism, cyanide, and OP poisoning. These crucial outcomes underscore the breadth of current research covering a variety of chemical threats. Overall, this collection of articles highlights the importance of ongoing research and development in the field of MCs, emphasizing the potential of these countermeasures to effectively treat and mitigate the effects of toxicant exposures and thereby enhance our preparedness for mass casualty incidents. SIGNIFICANCE STATEMENT: CBRN agents pose a significant threat to public health. Effective MCs exist for certain chemical threats, but there is a need for new and improved MCs for many others. The research presented in this special issue of JPET highlights the latest advancements in MCs for CBRN threats. This research has the potential to lead to the development of new and repurposed MCs that are more effective, broad-spectrum, and easier to administer to mitigate acute and long-term consequences of chemical exposures.