Response of the hepatic and renal macrophage pool to novel spiro-linked heterocyclic compounds in rats

Background: The development of modern cancer therapies and new chemotherapeutic agents is ongoing. Heterocyclic compounds attract particular interest as promising therapeutic agents in the field of antitumor drug synthesis. A method for synthesizing spiro-linked pharmacophore fragments has recently been developed, resulting in spiro-linked barbiturates and oxindoles, a fundamentally new class of spirocyclic cycloadducts with expected antitumor activity. To assess the potential side effects of these novel compounds, it is crucial to evaluate their impact at the tissue and cellular levels, particularly on the liver and kidneys, as well as on macrophages, a critical component of the hepatic and renal mononuclear phagocyte system. Hepato- and nephrotoxicity are well-known adverse effects of many cytotoxic agents. Aim: The work aimed to assess the response of the hepatic and renal macrophage pool to novel spiro-linked heterocyclic compounds in rats. Methods: Male Wistar rats were divided into three groups. Animals in the control group received a single intraperitoneal injection of 1 mL of 0.9% sodium chloride solution. The other two groups received a single intraperitoneal injection of 1 mL of either a spiro-linked barbiturate (Compound 1; EG I) or a spiro-linked oxindole (Compound 2; EG II) at a dose of 12 mg/kg body weight. Animals were euthanized 2, 4, and 8 weeks after dosing. Tissue sections (5 µm thick) were prepared using standard histological techniques and stained with hematoxylin and eosin. Macrophages were detected immunocytochemically using anti-CD68 antibodies. Results: Morphological analysis of the liver revealed endotheliitis in both experimental groups. Morphometric evaluation of the Kupffer cell pool demonstrated a significant increase in their number in EG I and EG II at all time points. Morphological analysis of the kidneys showed increased glomerular cellularity in both experimental groups, along with mild diffuse focal lymphomonocytic infiltration of the interstitium, which was more pronounced in EG II. The number of macrophages significantly increased in both experimental groups at 2 and 4 weeks, returning to control levels in EG I by week 8. In EG II, it remained significantly elevated compared with both the control and EG I groups. Conclusion: Morphological examination indicated that the liver was the most sensitive to a single dose of the tested compounds. Reactive changes in the hepatic macrophage pool were observed in both experimental groups at all time points. The kidneys also responded to both compounds, with more pronounced changes in macrophage numbers in EG II. The macrophage pool response to the administered compounds in the examined organs was identical, with the spiro-linked oxindole showing a slightly greater toxic effect.