Pharmacodynamic effects of the murine p75-Fc fusion protein in mice

TNF or EGFR inhibition equally block AKI-to-CKD transition: opportunities for etanercept treatment

BACKGROUND

Inflammation is a key driver of the transition of acute kidney injury to progressive fibrosis and chronic kidney disease (AKI-to-CKD transition). Blocking a-disintegrin-and-metalloprotease-17 (ADAM17)-dependent ectodomain shedding, in particular of epidermal growth factor receptor (EGFR) ligands and of the type 1 inflammatory cytokine tumor necrosis factor (TNF), reduces pro-inflammatory and pro-fibrotic responses after ischemic AKI or unilateral ureteral obstruction (UUO), a classical fibrosis model. Metalloprotease or EGFR inhibition show significant undesirable side effects in humans. In retrospective studies anti-TNF biologics reduce the incidence and progression of CKD in humans. Whether TNF has a role in AKI-to-CKD transition and how TNF inhibition compares to EGFR inhibition is largely unknown.

METHODS

Mice were subjected to bilateral renal ischemia-reperfusion injury or unilateral ureteral obstruction. Kidneys were analyzed by histology, immunohistochemistry, qPCR, western blot, mass cytometry, scRNA sequencing, and cytokine profiling.

RESULTS

Here we show that TNF or EGFR inhibition reduce AKI-to-CKD transition and fibrosis equally by about 25%, while combination has no additional effect. EGFR inhibition reduced kidney TNF expression by about 50% largely by reducing accumulation of TNF expressing immune cells in the kidney early after AKI, while TNF inhibition did not affect EGFR activation or immune cell accumulation. Using scRNAseq data we show that TNF is predominantly expressed by immune cells in AKI but not in proximal tubule cells (PTC), and PTC-TNF knockout did not affect AKI-to-CKD transition in UUO. Thus, the anti-inflammatory and anti-fibrotic effects of the anti-TNF biologic etanercept in AKI-to-CKD transition rely on blocking TNF that is released from immune cells recruited or accumulating in response to PTC-EGFR signals.

CONCLUSION

Short-term anti-TNF biologics during or after AKI could be helpful in the prevention of AKI-to-CKD transition.

iRhom2 promotes lupus nephritis through TNF-α and EGFR signaling

Lupus nephritis (LN) often results in progressive renal dysfunction. The inactive rhomboid 2 (iRhom2) is a newly identified key regulator of A disintegrin and metalloprotease 17 (ADAM17), whose substrates, such as TNF-α and heparin-binding EGF (HB-EGF), have been implicated in the pathogenesis of chronic kidney diseases. Here, we demonstrate that deficiency of iRhom2 protects the lupus-prone Fcgr2b-/- mice from developing severe kidney damage without altering anti-double-stranded DNA (anti-dsDNA) Ab production by simultaneously blocking HB-EGF/EGFR and TNF-α signaling in the kidney tissues. Unbiased transcriptome profiling of kidneys and kidney macrophages revealed that TNF-α and HB-EGF/EGFR signaling pathways are highly upregulated in Fcgr2b-/- mice, alterations that were diminished in the absence of iRhom2. Pharmacological blockade of either TNF-α or EGFR signaling protected Fcgr2b-/- mice from severe renal damage. Finally, kidneys from LN patients showed increased iRhom2 and HB-EGF expression, with interstitial HB-EGF expression significantly associated with chronicity indices. Our data suggest that activation of iRhom2/ADAM17-dependent TNF-α and EGFR signaling plays a crucial role in mediating irreversible kidney damage in LN, thereby uncovering a target for selective and simultaneous dual inhibition of 2 major pathological pathways in the effector arm of the disease.

Adjunctive TNF inhibition with standard treatment enhances bacterial clearance in a murine model of necrotic TB granulomas

BACKGROUND

It has been hypothesized that early host-responses during TB treatment may paradoxically promote survival of persistent bacteria. We therefore evaluated whether adjunctive inhibition of tumor necrosis factor alpha (TNF-α)-a key cytokine in host responses against TB-could hasten bacterial clearance in a mouse strain that develops necrotic lesions in response to Mycobacterium tuberculosis infection.

METHODOLOGY/PRINCIPAL FINDINGS

Six weeks after an aerosol infection, C3HeB/FeJ mice received standard TB treatment with or without adjunctive TNF inhibition (etanercept for the initial six weeks). Functional TNF-α levels and lung pathology were found to be reduced in the mice receiving etanercept. Compared to standard TB treatment, the addition of etanercept resulted in a significantly lower pulmonary bacterial burden, corresponding to the phase when a significant proportion of bacteria are multiplying slowly (p<0.0233). Finally, only 10.5% of mice receiving adjunctive etanercept versus 27.8% receiving standard TB treatment alone relapsed.

CONCLUSION

This study provides proof-of-principle that modulation of TNF-α activity can hasten bacterial clearance during standard multi-drug TB treatment. Oral agents that modulate TNF-α should therefore be considered as adjunct therapies for shortening TB treatments. However, due to concerns of reactivation disease, additional studies need to be performed before TNF-α inhibitors are used for TB treatment in humans.

Systemic inflammation sensitizes the neonatal brain to excitotoxicity through a pro-/anti-inflammatory imbalance: key role of TNFalpha pathway and protection by etanercept

Systemic inflammation sensitizes the perinatal brain to an ischemic/excitotoxic insult but the mechanisms are poorly understood. We hypothesized that the mechanisms involve an imbalance between pro- and anti-inflammatory factors. A well characterized mouse model where a systemic injection of IL-1beta during the first five postnatal days (inflammatory insult) is combined with an intracerebral injection of the glutamatergic analogue ibotenate (excitotoxic insult) at postnatal day 5 was used. Following the inflammatory insult alone, there was a transient induction of IL-1beta and TNFalpha, compared with controls measured by quantitative PCR, ELISA, and Western blot. Following the combined inflammatory and excitotoxic insult, there was an induction of IL-1beta, TNFalpha, and IL-6 but not of IL-10 and TNFR1, indicating an altered pro-/anti-inflammatory balance after IL-1beta sensitized lesion. We then tested the hypothesis that the TNFalpha pathway plays a key role in the sensitization and insult using TNFalpha blockade (etanercept) and TNFalpha(-/-) mice. Etanercept given before the insult did not affect brain damage, but genetic deletion of TNFalpha or TNFalpha blockade by etanercept given after the combined inflammatory and excitotoxic insult reduced brain damage by 50%. We suggest this protective effect was centrally mediated, since systemic TNFalpha administration in the presence of an intact blood-brain barrier did not aggravate the damage and etanercept almost abolished cerebral TNFalpha production. In summary, sensitization was, at least partly, mediated by an imbalance between pro- and anti-inflammatory cytokines. Cerebral TNFalpha played a key role in mediating brain damage after the combined inflammatory and excitatory insult.

The role of interleukin-6 in lipopolysaccharide-induced fever by mechanisms independent of prostaglandin E2

Fever has been shown to be elicited by prostaglandin E(2) (PGE(2)) binding to its receptors on thermoregulatory neurons in the anterior hypothalamus. The signals that trigger PGE(2) production are thought to include proinflammatory cytokines, such as IL-6. However, although the presence of IL-6 is critical for fever, IL-6 by itself is not or only weakly pyrogenic. Here we examined the relationship between IL-6 and PGE(2) in lipopolysaccharide (LPS)-induced fever. Immune-challenged IL-6 knockout mice did not produce fever, in contrast to wild-type mice, but the expression of the inducible PGE(2)-synthesizing enzymes, cyclooxygenase-2 and microsomal prostaglandin E synthase-1, was similarly up-regulated in the hypothalamus of both genotypes, which also displayed similarly elevated PGE(2) levels in the cerebrospinal fluid. Nevertheless, both wild-type and knockout mice displayed a febrile response to graded concentrations of PGE(2) injected into the lateral ventricle. There was no major genotype difference in the expression of IL-1beta and TNFalpha or their receptors, and pretreatment of IL-6 knockout mice with soluble TNFalpha receptor ip or intracerebroventricularly or a cyclooxygenase-2 inhibitor ip did not abolish the LPS unresponsiveness. Hence, although IL-6 knockout mice have both an intact PGE(2) synthesis and an intact fever-generating pathway downstream of PGE(2), endogenously produced PGE(2) is not sufficient to produce fever in the absence of IL-6. The findings suggest that IL-6 controls some factor(s) in the inflammatory cascade, which render(s) IL-6 knockout mice refractory to the pyrogenic action of PGE(2), or that it is involved in the mechanisms that govern release of synthesized PGE(2) onto its target neurons.