Toxicologic Pathology Forum: Considerations Regarding Determination of Adversity for Immunopathology Findings in Nonclinical Toxicology Studies with Immune-Modulating Therapeutics

The evaluation of changes in the immune system serves to determine the efficacy and potential immunotoxicologic effects of new products under development. Toxicologic pathologists play critical roles in identifying immune system changes that drive the immunosafety determination. Standard pathology evaluations of therapies and chemicals remain similar; however, biopharmaceutical therapies have moved from simply affecting the immune system to being specifically developed to modify the immune system, which can impact interpretation. Recent explosive growth in immunomodulatory therapies presents a challenge to the toxicologic pathologist, toxicologist, and regulatory reviewer in terms of evaluating the clinical relevance and potential adversity of immune system changes. Beyond the recognition of such changes, there is an increasing expectation to evaluate, describe, and interpret how therapies affect complex immune system pathways for both immunomodulatory therapies and non-immunomodulatory drugs with off-target immunotoxic effects. In this opinion piece, considerations regarding immune system evaluation, the current landscape of immunomodulatory therapies, a brief description of immunotoxicologic (and immunopathologic) endpoints, the importance of integrating such immunosafety data, and relevance to adversity determination are discussed. Importantly, we describe how the current paradigm of determining adversity for immune system changes may be challenging or insufficient and propose a harmonized and flexible approach for assessing adversity.

Pretreatment with a novel Toll-like receptor 4 agonist attenuates renal ischemia-reperfusion injury

Acute kidney injury (AKI) is common in surgical and critically ill patients. This study examined whether pretreatment with a novel Toll-like receptor 4 agonist attenuated ischemia-reperfusion injury (IRI)-induced AKI (IRI-AKI). We performed a blinded, randomized-controlled study in mice pretreated with 3-deacyl 6-acyl phosphorylated hexaacyl disaccharide (PHAD), a synthetic Toll-like receptor 4 agonist. Two cohorts of male BALB/c mice received intravenous vehicle or PHAD (2, 20, or 200 µg) at 48 and 24 h before unilateral renal pedicle clamping and simultaneous contralateral nephrectomy. A separate cohort of mice received intravenous vehicle or 200 µg PHAD followed by bilateral IRI-AKI. Mice were monitored for evidence of kidney injury for 3 days postreperfusion. Kidney function was assessed by serum blood urea nitrogen and creatinine measurements. Kidney tubular injury was assessed by semiquantitative analysis of tubular morphology on periodic acid-Schiff (PAS)-stained kidney sections and by kidney mRNA quantification of injury [neutrophil gelatinase-associated lipocalin (Ngal), kidney injury molecule-1 (Kim-1), and heme oxygenase-1 (Ho-1)] and inflammation [interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (Tnf-α)] using quantitative RT-PCR. Immunohistochemistry was used to quantify proximal tubular cell injury and renal macrophages by quantifying the areas stained with Kim-1 and F4/80 antibodies, respectively, and TUNEL staining to detect the apoptotic nuclei. PHAD pretreatment yielded dose-dependent kidney function preservation after unilateral IRI-AKI. Histological injury, apoptosis, Kim-1 staining, and Ngal mRNA were lower in PHAD-treated mice and IL-1β mRNA was higher in PHAD-treated mice. Similar pretreatment protection was noted with 200 mg PHAD after bilateral IRI-AKI, with significantly reduced Kim-1 immunostaining in the outer medulla of mice treated with PHAD after bilateral IRI-AKI. In conclusion, PHAD pretreatment leads to dose-dependent protection from renal injury after unilateral and bilateral IRI-AKI in mice.NEW & NOTEWORTHY Pretreatment with 3-deacyl 6-acyl phosphorylated hexaacyl disaccharide; a novel synthetic Toll-like receptor 4 agonist, preserves kidney function during ischemia-reperfusion injury-induced acute kidney injury.

A Single Nucleotide Polymorphism in SH2B3/LNK Promotes Hypertension Development and Renal Damage

BACKGROUND

SH2B3 (SH2B adaptor protein 3) is an adaptor protein that negatively regulates cytokine signaling and cell proliferation. A common missense single nucleotide polymorphism in SH2B3 (rs3184504) results in substitution of tryptophan (Trp) for arginine (Arg) at amino acid 262 and is a top association signal for hypertension in human genome-wide association studies. Whether this variant is causal for hypertension, and if so, the mechanism by which it impacts pathogenesis is unknown.

METHODS

We used CRISPR-Cas9 technology to create mice homozygous for the major (Arg/Arg) and minor (Trp/Trp) alleles of this SH2B3 polymorphism. Mice underwent angiotensin II (Ang II) infusion to evaluate differences in blood pressure (BP) elevation and end-organ damage including albuminuria and renal fibrosis. Cytokine production and Stat4 phosphorylation was also assessed in Arg/Arg and Trp/Trp T cells.

RESULTS

Trp/Trp mice exhibit 10 mmHg higher systolic BP during chronic Ang II infusion compared to Arg/Arg controls. Renal injury and perivascular fibrosis are exacerbated in Trp/Trp mice compared to Arg/Arg controls following Ang II infusion. Renal and ex vivo stimulated splenic CD8+ T cells from Ang II-infused Trp/Trp mice produce significantly more interferon gamma (IFNg) compared to Arg/Arg controls. Interleukin-12 (IL-12)-induced IFNg production is greater in Trp/Trp compared to Arg/Arg CD8+ T cells. In addition, IL-12 enhances Stat4 phosphorylation to a greater degree in Trp/Trp compared to Arg/Arg CD8+ T cells, suggesting that Trp-encoding SH2B3 exhibits less negative regulation of IL-12 signaling to promote IFNg production. Finally, we demonstrated that a multi-SNP model genetically predicting increased SH2B3 expression in lymphocytes is inversely associated with hypertension and hypertensive chronic kidney disease in humans..

CONCLUSIONS

Taken together, these results suggest that the Trp encoding allele of rs3184504 is causal for BP elevation and renal dysfunction, in part through loss of SH2B3-mediated repression of T cell IL-12 signaling leading to enhanced IFNg production.

International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Nonproliferative and Proliferative Lesions of the Rabbit

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally accepted nomenclature for proliferative and non-proliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in most tissues and organs from the laboratory rabbit used in nonclinical safety studies. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. Relevant infectious and parasitic lesions are included as well. A widely accepted and utilized international harmonization of nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.

Symmetric Dimethylarginine Is a Sensitive Biomarker of Glomerular Injury in Rats

Glomerular filtration rate is the gold-standard method for assessment of renal function but is rarely performed in routine toxicity studies. Standard serum biomarkers of renal function are insensitive and become elevated only with significant loss of organ function. Symmetric dimethylarginine (SDMA) is a ubiquitous analyte that is freely filtered by the glomerulus and can be detected in serum. It has shown utility for the detection of renal injury in dogs and cats in clinical veterinary practice, but the potential utility of SDMA to detect renal injury in preclinical species or toxicity studies has not been thoroughly investigated. We utilized a well-characterized glomerular toxicant, puromycin aminonucleoside, to induce podocyte injury and subsequent proteinuria in young male Sprague-Dawley rats. At the end of 1 or 2 weeks, blood, urine, and kidney tissue were collected for analysis. One week following a single 50 mg/kg dose, urea nitrogen, creatinine, and albumin mean values were within historical control ranges, while SDMA was increased. Glomerular changes in these animals included periodic acid-Schiff positive globules within podocytes, podocyte hypertrophy by light microscopy, and podocyte degeneration with effacement of foot processes by electron microscopy (EM). Taken together, our data indicate that SDMA may be a useful biomarker for early detection of glomerular toxicities in rats.

Hypoxia inducible factor signaling in breast tumors controls spontaneous tumor dissemination in a site-specific manner

Hypoxia is a common feature in tumors and induces signaling that promotes tumor cell survival, invasion, and metastasis, but the impact of hypoxia inducible factor (HIF) signaling in the primary tumor on dissemination to bone in particular remains unclear. To better understand the contributions of hypoxia inducible factor 1 alpha (HIF1α), HIF2α, and general HIF pathway activation in metastasis, we employ a PyMT-driven spontaneous murine mammary carcinoma model with mammary specific deletion of Hif1α, Hif2α, or von Hippel-Lindau factor (Vhl) using the Cre-lox system. Here we show that Hif1α or Hif2α deletion in the primary tumor decreases metastatic tumor burden in the bone marrow, while Vhl deletion increases bone tumor burden, as hypothesized. Unexpectedly, Hif1α deletion increases metastatic tumor burden in the lung, while deletion of Hif2α or Vhl does not affect pulmonary metastasis. Mice with Hif1α deleted tumors also exhibit reduced bone volume as measured by micro computed tomography, suggesting that disruption of the osteogenic niche may be involved in the preference for lung dissemination observed in this group. Thus, we reveal that HIF signaling in breast tumors controls tumor dissemination in a site-specific manner.

Abstract 2878: HIF signaling in breast tumors controls spontaneous tumor dissemination in a site-specific manner

As tumors outgrow their blood supply, they frequently become hypoxic, activating hypoxia-inducible factor (HIF) signaling. Previous studies suggest that HIF signaling in breast cancer cells promotes lung dissemination in genetic models and bone colonization following intracardiac inoculation, but the impact of HIF signaling in the primary tumor on spontaneous dissemination to bone has never been evaluated. Thus, we hypothesized that Hif1α or Hif2α deletion in the primary tumor would reduce spontaneous dissemination to lung and bone, while deletion of Vhl (resulting in constitutive HIF signaling) would increase dissemination to distant metastatic sites. To test this, we generated MMTV-Cre.Hif1αf/f.PyMT, MMTV-Cre.Hif2αf/f.PyMT, and MMTV-Cre.Vhlf/f.PyMT mice, which spontaneously develop mammary carcinomas with conditional deletion of Hif1a, Hif2a, or Vhl, respectively. Littermate and cousin controls were used for all experiments. All mice were euthanized when the largest tumor reached 1cm in any dimension. Tumor growth was significantly delayed in Hif1α-/- (n=21) and Vhl-/- mice (n=19), while Hif2α-/- mice (n=18) had similar tumor progression compared to wildtype controls (n=19-20). Despite the delay in tumor growth, Hif1α-/- mice had greater total tumor weight (71%, p<0.01) and Vhl-/- mice had reduced total tumor weight (31%, p<0.05) on average compared to wildtype mice, with no difference in Hif2α-/- mice. Surprisingly, histological inspection of lung sections revealed that Hif1α-/- mice had greater incidence of macroscopic tumor nodules (n=15/21 Hif1α-/-, n=6/19 Hif1αf/f, p<0.05), and greater average lesion number and area (1.9- and 2.2-fold, respectively, p<0.05), but there was no difference in Ki67 staining in the lung nodules. In contrast, bone dissemination was significantly reduced in Hif1α-/- (56%, p<0.05) and Hif2α-/- mice (43%, p<0.01) and significantly increased in Vhl-/- mice (238%, p<0.01) as assessed by flow cytometry. However, there was no change in the expression of an 89-gene panel of metastasis associated genes or markers of EMT (Cdh1/2, Egfr, Notch1, Snai1-3, Twist1, Zeb1/2) or autophagy (Atg7, Becn1, Map1lc3a/b, Sqstm1, Ulk1) in Hif1α-/- primary tumors. None of the three transgenic strains showed a difference in dissemination to liver or brain. These data indicate that while both HIF1α and HIF2α drive tumor dissemination to bone, HIF1α is also essential for preventing metastatic outgrowth in the lung. It is therefore likely that the increase in bone dissemination when mammary fat pad VHL is deleted is due to elevated HIF1α and HIF2α signaling. Taken together, these data indicate a critical, yet divergent, role of HIF signaling in dissemination to bone and lung. Thus, targeted inhibition of HIF1α or HIF2α could be beneficial in preventing bone metastasis but may promote the outgrowth of lung-disseminated breast cancer cells.

Citation Format: Vera M. Todd, Lawrence A. Vecchi, Katherine P. Snow, Lauren Himmel, Marjan Rafat, Rachelle W. Johnson. HIF signaling in breast tumors controls spontaneous tumor dissemination in a site-specific manner [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2878.

Abstract MP43: The Minor Allele Of A Single Nucleotide Polymorphism In SH2B3 Promotes Hypertension And Renal Dysfunction In Mice

SH2B3, also known as LNK, is an adaptor protein that negatively regulates growth factor and cytokine signaling. The minor allele of a single nucleotide polymorphism in SH2B3 (rs3184504) encodes a tryptophan (Trp) at amino acid 262 as opposed to arginine (Arg) and is strongly associated with hypertension in genome-wide association studies. Whether this variant is causal and how it impacts hypertension development and end-organ damage is unknown. We used CRISPR-Cas9 to engineer mice homozygous for the major and minor alleles of this SH2B3 polymorphism, resulting in Arg/Arg and Trp/Trp mice, respectively. Trp/Trp mice exhibited increased systolic blood pressure (SBP) by radiotelemetry during weeks 3-4 of angiotensin II (Ang II) infusion compared to Arg/Arg mice (nighttime SBP 168 vs 158 mm Hg, respectively). Renal dysfunction was also exacerbated in Ang II-treated Trp/Trp compared to Arg/Arg mice, as evidenced by significantly increased urinary albumin/creatinine ratio (0.41 vs 0.17), renal perivascular fibrosis (fibrosis score 2.0 vs 1.0), and renal macrophages (8,341 vs 6,413 per kidney). In addition, renal CD8 + T cells from Ang II-treated Trp/Trp mice produced significantly more IFNγ compared to Arg/Arg controls (median fluorescence intensity 20,455 vs 14,134), and ex vivo stimulated splenic CD8 + T cells from Trp/Trp compared to Arg/Arg mice made 2.7-fold more IFNγ. To determine a mechanism for increased T cell IFNγ production, dendritic cells and naïve T cells from Trp/Trp and Arg/Arg mice were co-cultured in different combinations. The greatest increase in GM-CSF-induced IFNγ production occurred when both dendritic cells and T cells came from Trp/Trp mice (3.4-fold greater than both cell types from Arg/Arg mice). This effect appears to be due to loss of SH2B3-mediated suppression of GM-CSF signaling, as overexpression of Trp-encoding SH2B3 in HEK cells exhibited significantly less repression of GM-CSF-induced Stat5 activation compared to Arg-encoding SH2B3. Taken together, these findings suggest that the Trp encoding allele of rs3184504 is a causal variant promoting blood pressure elevation and renal dysfunction, at least in part through loss of SH2B3-mediated repression of T cell IFNγ production.

Nodular typhlocolitis, heterakiasis, and mesenchymal neoplasia in a ring-necked pheasant (Phasianus colchicus) with immunohistochemical characterization of visceral metastases

A 9-y-old, male ring-necked pheasant ( Phasianus colchicus) was autopsied following euthanasia because of acute distress, recumbency, and dyspnea. The bird had experienced a protracted period of neuromuscular disease localized to the left sciatic nerve. Gross and histologic examination of the large intestine revealed intramural nodules predominantly comprised of atypical, whorling spindle cells with small cores of granulomatous inflammation centered on cross-sections of immature adult nematodes. The body structures of these metazoan organisms and clinical disease manifestation are consistent with Heterakis isolonche infection. Nodular spindle cell proliferations without granulomatous inflammation or intralesional nematodes were also found throughout the liver and lungs, suggesting metastasis from the intestine. Immunohistochemical staining of the hepatic and pulmonary tumor tissue with vimentin and S100 suggests a neurofibroblastic origin.

Necrotizing hepatitis in a domestic pigeon (Columba livia)

An adult male domestic pigeon (Columba livia) was presented for necropsy following natural death after a period of chronic weight loss and severe intestinal ascariasis. Histopathologic examination of the liver found moderate to marked, multifocal necrotizing hepatitis with large, basophilic intranuclear inclusion bodies. Transmission electron microscopy of affected hepatocytes demonstrated numerous intra- and perinuclear icosahedral virions arranged in a lattice structure, consistent with adenoviral infection.