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Abstract: "Severe acute respiratory syndrome coronavirus-2" (SARS-CoV-2) infection has variable described dermatologic manifestations. "COVID (coronavirus disease) toes" became a hallmark of the disease in young and largely asymptomatic patients, who may have negative test results for SARS-CoV-2. Pernio (chilblains)-like lesions are seen mostly in infected pediatric patients and are purple painful, frequently bilateral, ill-defined plaques with prominent inflammation on histological examination. In contrast to pernio-like presentation in children, critically ill adult patients with SARS-CoV-2 develop "purple" digits that may be sharply demarcated and may demonstrate asymmetric areas of ischemia. These 2 contrasting entities are sometimes grouped together as "COVID toes" due to some similarities in clinical appearance and presentation. Here, we summarize histopathologic examination from an autopsy, including the cutaneous lesions from the affected and normal contralateral toes and correlate them with systemic findings. In contrast to pernio-like lesions, the skin of the affected necrotic toes contained thrombi in vessels without prominent inflammation, suggestive of an embolic event. This is further supported by the clinical history of and autopsy findings of popliteal artery thrombus and multiple subsegmental pulmonary emboli. Our findings suggest that critically ill patients with SARS-CoV-2 have different pathological processes affecting skin at peripheral sites (ie, fingers, toes, ears, and nose), which may be due to thromboembolic events. The skin is a mirror of the body and skin pathology may shed light into overall pathogenesis of systemic illness and processes., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Nitric oxide synthase (NOS)-2 is expressed during acute cardiac allograft rejection in association with death of heart muscle cells. The nuclear enzyme poly(adenosine diphosphate [ADP]-ribose) synthase (PARS) is activated by agonists such as NO and peroxynitrite, which cause single-strand DNA breaks; PARS, in turn can promote both necrosis and apoptosis. To investigate the hypothesis that NO produced by NOS-2 in cardiomyocytes activates PARS and contributes to heart muscle cell death by apoptosis, experiments were performed using a heterotopic rat abdominal heart transplant model and cytokine-stimulated heart muscle cells in tissue culture., Methods: Cardiac allografts were treated after transplantation with either the PARS inhibitor 5-aminoisoquinolinone at 3 mg/kg subcutaneously daily or with vehicle. Isolated purified adult rat cardiomyocytes incubated with cytokines to induce NOS-2 were treated in vitro with another PARS inhibitor, 3-aminobenzamide (3AB)., Results: PARS inhibition increased cardiac-allograft survival from 6 +/- 2 to 10 +/- 3 days (n=6, n=6, P<0.05). The inflammatory infiltrate, NOS-2-positive macrophages, myocyte apoptosis, and myocyte content of nitrotyrosine and poly(ADP-ribose) were significantly decreased in PARS inhibited allografts at day 5 posttransplantation. Similarly, apoptosis and PARS activity were diminished in cytokine-stimulated adult rat cardiomyocytes when either 3AB or L-NMMA were applied., Conclusions: The data indicate that PARS activation occurs during acute cardiac-allograft rejection and contributes significantly to the inflammatory response and to the death of cardiac muscle cells by apoptosis. They suggest that PARS inhibition combined with immunosuppression might enhance salvage of heart-muscle cells during acute cardiac-allograft rejection.

Background: Drugs that selectively block nitric oxide synthase (NOS) 2 enzyme activity by inhibiting dimerization of NOS2 monomers have recently been developed., Methods and Results: To investigate whether selective inhibition of NOS2 is cardioprotective, rats were pretreated for 2 days with BBS2, an inhibitor of NOS2 dimerization, at 15 mg/kg SC. Isolated buffer-perfused hearts from treated (n=9) and control (n=7) hearts were subjected to 20 minutes of ischemia followed by 60 minutes of reperfusion. NOS2 protein was upregulated in all hearts at the end of ischemia and of reperfusion; NOS2 enzyme activity was 60% lower in hearts from the treated animals. In the treated hearts, the increase in end-diastolic pressure was significantly attenuated at the end of ischemia, and the return of developed pressure at reperfusion was greater (P<0.05). Creatine kinase release at reperfusion was lower in treated hearts than in controls (P=0.02). At the end of ischemia and of reperfusion, myocardial ATP levels were significantly higher in the treated hearts than in controls (P<0.05). In the treated hearts under ischemic conditions, lactate content was higher and the lactate/pyruvate ratio was lower than in controls (P<0.05); GAPDH activity was higher; and G-3-P and aldose reductase activity were lower. At reperfusion, in the treated hearts, there was less histological damage and less apoptosis of cardiac muscle cells., Conclusions: Pretreatment with BBS2, a selective inhibitor of NOS2, improves contractile performance, preserves myocardial ATP, and reduces damage and death of cardiac myocytes during ischemia and reperfusion of isolated buffer-perfused rat hearts.

Background: Using a rat (Lewis-Wistar Furth) abdominal heterotopic transplantation model, we reported previously that the expression of cyclooxygenase (COX)-2 is increased in parallel with that of nitric oxide synthase (NOS)-2 during cardiac allograft rejection., Methods: To investigate effects of COX-2 inhibition in this model, allograft recipients were treated orally (PO) with 5 mg/kg per day of the tetra substituted furanone selective COX-2 inhibitor 5,5-dimethyl-3-(3 fluorophenyl)-4-(4 methylsulfonal) phenyl-2 (5H)-furanone (DFU) in 1% methyl cellulose solution., Results: In the treated animals, allograft survival was increased from 6.3+/-0.5 to 12.6+/-2.6 days (P = .001). At days 3 and 5 posttransplantation, there were reductions in the extent of the inflammatory infiltrate, endovasculitis, myocardial edema, and cardiomyocyte damage in rejecting allografts. The mean numbers of apoptotic cardiomyocytes determined with the terminal deoxynucleotide transferase-mediated dUTP nick-end labeling (TUNEL) technique were significantly reduced in DFU-treated grafts compared with untreated controls (P < 0.05). At day 3 posttransplantation, prostaglandin E2 synthesis by myocardial slices incubated with 100 microM bradykinin was reduced from 1,097+/-156 to 153+/-63 pg/mg of protein in the treated allografts (P < .005). At day 5, COX-2 protein and mRNA together with COX-2, NOS-2, and nitrotyrosine immunostaining in damaged cardiomyocytes were diminished in treated versus control grafts., Conclusion: The data indicate that the inhibition of COX-2 prolongs allograft survival and reduces myocardial damage and inflammation during acute cardiac allograft rejection.

Background: Nitric oxide synthase-2 (NOS2) is expressed during acute cardiac allograft rejection in association with myocardial inflammation, contractile dysfunction, and death of cardiomyocytes by necrosis and apoptosis. Recently, allosteric inhibitors of NOS2 monomer dimerization that block NOS2 activity have been developed., Methods and Results: To investigate effects of selective NOS2 blockade, 15 mg/kg of BBS-1 or BBS-2 was administered twice daily subcutaneously to rats starting the day of heterotopic heart transplantation. Cardiac allograft survival was increased significantly, from 6.8 days in controls to 13.3 and to 14.2 days in NOS2-inhibited allografts. At day 5 after heart transplantation, synthesis of NOx was reduced by 53%. There were significantly fewer T lymphocytes and macrophages in the inflammatory infiltrate, as well as less edema and cardiomyocyte damage, and the International Society of Heart and Lung Transplantation score fell from 5 to 4 and 3.5. NOS2 and nitrotyrosine immunostaining and the mean numbers of apoptotic cells and of apoptotic cardiomyocytes were significantly diminished in the treated allografts., Conclusions: The data indicate that selective inhibition of NOS2 dimerization prolongs survival and reduces myocardial inflammation and cardiomyocyte damage in acute cardiac allograft rejection.

Recent studies have indicated that the use of the MIB-1 immunostaining may be useful in distinguishing endocervical neoplasia from benign nonneoplastic lesions. We sought to investigate this finding further with a specific emphasis on the common benign processes that may result in a nonspecific increase of MIB-1 staining. In this study we quantified the MIB-1 immunostaining in the mucinous endocervical epithelium (n=45) and in tubal metaplasia (n=28) during the proliferative and secretory phases (hormonal influence), in the mucinous endocervical epithelium in cases of cervicitis (inflammation) (n=10), in cases with a history of a recent biopsy (regeneration) (n=15), endocervical polyps (benign growth) (n=8), in the endocervical glands adjacent to a squamous intraepithelial lesion (human papilloma virus [HPV] infection) (n=63), and in in situ and invasive cervical adenocarcinomas (n=30). All cases with increased MIB-1 staining were subsequently tested for the presence of HPV DNA. The range of MIB-1 staining in the benign endocervical epithelium was from 0% to 48% and in the neoplastic epithelium from 25% to 84%. MIB-1 staining below 10% always reflected a benign process and MIB-1 staining higher than 50% was always associated with a neoplasia. Rare benign cases (tubal metaplasia during the proliferative phase, glands adjacent to squamous intraepithelial lesions, and cases with a history of a recent biopsy) had increased MIB-1 index, which overlapped with the neoplastic cases. In conclusion, MIB-1 is a useful marker of endocervical neoplasia, although in rare cases an overlap between benign and neoplastic cases may exist.

Background: The contribution of nitric oxide synthase (NOS)-2 to myocardial inflammation and cardiomyocyte necrosis and apoptosis during allograft rejection was investigated through heterotopic cardiac transplantation in mice., Methods and Results: In the first experiments, hearts from C3H donor mice were transplanted into NOS-2(-/-) and NOS-2(+/+) C57BL/6J.129J recipients. A second series of experiments included NOS-2(-/-) donor hearts transplanted into NOS-2(-/-) recipients and wild-type NOS-2(+/+) donor hearts transplanted into wild-type NOS-2(+/+) recipients. (All donors were C57BL/6J and recipients were C57BL/6J.129J.) In the first series of experiments, no significant differences were observed in allograft survival, rejection score, total number of apoptotic nuclei (TUNEL), total number of apoptotic cardiomyocytes, or graft NOS-2 mRNA and protein. Positive NOS-2 immunostaining occurred in endothelial cells and cardiomyocytes in the allografts; the inflammatory infiltrate was NOS-2 positive only when recipients were NOS-2(+/+). In the second series of experiments, cardiac allograft survival was significantly increased in the NOS-2(-/-) mice (26+/-13 versus 17+/-8 days, P<0.05), along with significant reductions in inflammatory infiltrate, rejection score, and total number of apoptotic nuclei (23.5+/-9.5 versus 56.4+/-15.3, P<0.01) and of apoptotic cardiomyocytes (2.9+/-1.6 versus 6.9+/-2.7, P<0.05). No NOS-2 or nitrotyrosine, a marker of peroxynitrite exposure, was detected in NOS-2(-/-) allografts transplanted into NOS-2(-/-) recipients., Conclusions: The data suggest that NO derived from NOS-2 contributes to the inflammatory response and to cardiomyocyte damage and apoptosis during acute cardiac allograft rejection.

Background: The hypothesis that cyclooxygenase-2 (COX-2) is involved in the myocardial inflammatory response during cardiac allograft rejection was investigated using a rat heterotopic abdominal cardiac transplantation model., Methods and Results: COX-2 mRNA and protein in the myocardium of rejecting cardiac allografts were significantly elevated 3 to 5 days after transplantation compared with syngeneic controls (n=3, P<0.05). COX-2 upregulation paralleled in time and extent the upregulation of iNOS mRNA, protein, and enzyme activity in this model. COX-2 immunostaining was prominent in macrophages infiltrating the rejecting allografts and in damaged cardiac myocytes. Prostaglandin (PG) levels in rejecting allografts were also higher than in native hearts. Because NO has been reported to modulate PG synthesis by COX-2, additional transplants were performed using animals treated with a selective COX-2 inhibitor (SC-58125) and a selective inhibitor of the inducible nitric oxide synthase (iNOS) N-aminomethyl-L-lysine. At posttransplant day 5, inhibitor administration resulted in a significant reduction of COX-2 mRNA expression (3764+/-337 versus 5110+/-141 arbitrary units, n=3, P<0.05) and iNOS enzymatic activity (1.7+/-0.4 versus 22.8+/-14. 4 nmol/mg protein, n=3, P<0.01) compared with vehicle-treated allogeneic transplants. Allograft survival in treated animals was increased modestly from 5.4 to 6.4 days (P<0.05). However, apoptosis of cardiac myocytes (TUNNEL method) was only marginally reduced relative to vehicle controls in treated graft recipients. The intensity of allograft rejection was also similar in the treated and untreated allografts., Conclusions: The data indicates that COX-2 expression is enhanced in parallel with iNOS in the myocardium during cardiac allograft rejection.

Background: The mechanisms of myocyte death during cardiac allograft rejection are incompletely understood. In a previous study using a rat heterotopic cardiac allograft model, we showed that cardiac myocyte apoptosis, inducible nitric oxide synthase (iNOS) mRNA, protein and enzyme activity, and nitrotyrosine increased simultaneously during cardiac allograft rejection. This study was designed to investigate whether apoptosis and expression of iNOS occur in human cardiac allograft rejection., Methods: Right ventricular endomyocardial biopsies from 30 cases of allograft rejection (International Society of Heart and Lung Transplantation grade 3A/B) were compared with 12 biopsies with no rejection (International Society of Heart and Lung Transplantation grade 0). Samples were co-labeled for apoptosis and muscle actin. Serial sections were stained for iNOS, nitrotyrosine, and the leukocyte markers CD3, CD4, CD8, and CD68 to identify T-cell subpopulations and macrophages., Results: Biopsies with cardiac allograft rejection showed a 30-fold increase of apoptotic cells when compared with controls. Most apoptotic cardiac myocytes were found in proximity to macrophage (CD68+)-rich inflammatory infiltrates. iNOS immunoreactivity was strongest in macrophages and adjacent myocytes, which also showed high levels of nitrotyrosine, representing damage by peroxynitrite., Conclusions: Apoptosis is a major form of myocyte death during human cardiac allograft rejection. Cardiac myocyte apoptosis is closely associated with expression of iNOS in macrophages and myocytes and with nitration of myocyte proteins by peroxynitrite.