68Ga-DOTA-D-Alanine-BoroPro Radiotracer for Imaging of the Fibroblast Activation Protein in Malignant and Non-Malignant Diseases

Recently, we reported a new fibroblast activation protein (FAP) inhibitor radiopharmaceutical based on the 99mTc-((R)-1-((6-hydrazinylnicotinoyl)-D-alanyl) pyrrolidin-2-yl) boronic acid (99mTc-HYNIC-D-Alanine-BoroPro)(99mTc-HYNIC-iFAP) structure for tumor microenvironment SPECT imaging. This research aimed to synthesize 68Ga-[2,2',2″,2‴-(2-(4-(2-(5-(((S)-1-((S)-2-boronopyrrolidin-1-yl)-1-oxopropan-2-yl)carbamoyl)pyridin-2-yl)hydrazine-1-carbothioamido)benzyl)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetraacetic acid] (68Ga-DOTA-D-Alanine-BoroPro)(68Ga-iFAP) as a novel radiotracer for PET imaging and evaluate its usefulness for FAP expression in malignant and non-malignant tissues. The coupling of p-SCN-benzene DOTA with HYNIC-iFAP was used for the chemical synthesis and further labeling with 68Ga. Radiochemical purity was verified by radio-HPLC. The specificity of 68Ga-iFAP was evaluated in HCT116 cells, in which FAP expression was verified by immunofluorescence and Western blot. Biodistribution and biokinetic studies were performed in murine models. 68Ga-iFAP uptake at the myocardial level was assessed in mice with induced infarction. First-in-human images of 68Ga-iFAP in healthy subjects and patients with myocardial infarction, glioblastoma, prostate cancer, and breast cancer were also obtained. DOTA-D-Alanine BoroPro was prepared with a chemical purity of 98% and was characterized by UPLC mass spectroscopy, FT-IR, and UV-vis. The 68Ga-iFAP was obtained with a radiochemical purity of >95%. In vitro and in vivo studies demonstrated 68Ga-iFAP-specific recognition for FAP, rapid renal elimination, and adequate visualization of the glioblastoma, breast tumor, prostate cancer, and myocardial infarction sites. The results of this research justify further dosimetry and clinical trials to establish the specificity and sensitivity of 68Ga-iFAP PET for FAP expression imaging.

225Ac-iPSMA-RGD for Alpha-Therapy Dual Targeting of Stromal/Tumor Cell PSMA and Integrins

Prostate-specific membrane antigens (PSMAs) are frequently overexpressed in both tumor stromal endothelial cells and malignant cells (stromal/tumor cells) of various cancers. The RGD (Arg-Gly-Asp) peptide sequence can specifically detect integrins involved in tumor angiogenesis. This study aimed to preclinically evaluate the cytotoxicity, biokinetics, dosimetry, and therapeutic efficacy of 225Ac-iPSMA-RGD to determine its potential as an improved radiopharmaceutical for alpha therapy compared with the 225Ac-iPSMA and 225Ac-RGD monomers. HEHA-HYNIC-iPSMA-RGD (iPSMA-RGD) was synthesized and characterized by FT-IR, UV-vis, and UPLC mass spectroscopy. The cytotoxicity of 225Ac-iPSMA-RGD was assessed in HCT116 colorectal cancer cells. Biodistribution, biokinetics, and therapeutic efficacy were evaluated in nude mice with induced HCT116 tumors. In vitro results showed increased DNA double-strand breaks through ROS generation, cell apoptosis, and death in HCT116 cells treated with 225Ac-iPSMA-RGD. The results also demonstrated in vivo cytotoxicity in cancer cells after treatment with 225Ac-iPSMA-RGD and biokinetic and dosimetric properties suitable for alpha therapy, delivering ablative radiation doses up to 237 Gy/3.7 kBq to HCT116 tumors in mice. Given the phenotype of HCT116 cancer cells, the results of this study warrant further dosimetric and clinical studies to determine the potential of 225Ac-iPSMA-RGD in the treatment of colorectal cancer.

Synthesis and Evaluation of 177Lu-DOTA-PD-L1-i and 225Ac-HEHA-PD-L1-i as Potential Radiopharmaceuticals for Tumor Microenvironment-Targeted Radiotherapy

Current cancer therapies focus on reducing immunosuppression and remodeling the tumor microenvironment to inhibit metastasis, cancer progression, and therapeutic resistance. Programmed death receptor 1 (PD-1) is expressed on immune T cells and is one of the so-called checkpoint proteins that can suppress or stop the immune response. To evade the immune system, cancer cells overexpress a PD-1 inhibitor protein (PD-L1), which binds to the surface of T cells to activate signaling pathways that induce immune suppression. This research aimed to synthesize PD-L1 inhibitory peptides (PD-L1-i) labeled with lutetium-177 (177Lu-DOTA-PD-L1-i) and actinium-225 (225Ac-HEHA-PD-L1-i) and to preclinically evaluate their potential as radiopharmaceuticals for targeted radiotherapy at the tumor microenvironment level. Using PD-L1-i peptide as starting material, conjugation with HEHA-benzene-SCN and DOTA-benzene-SCN was performed to yield DOTA-PD-L1-i and HEHA-PD-L1-I, which were characterized by FT-IR, UV-vis spectroscopy, and HPLC. After labeling the conjugates with 225Ac and 177Lu, cellular uptake in HCC827 cancer cells (PD-L1 positive), conjugate specificity evaluation by immunofluorescence, radiotracer effect on cell viability, biodistribution, biokinetics, and assessment of radiation absorbed dose in mice with in duced lung micrometastases were performed. 225Ac-HEHA-PD-L1-i and 177Lu-DOTA-PD-L1-i, obtained with radiochemical purities of 95 ± 3% and 98.5 ± 0.5%, respectively, showed in vitro and in vivo specific recognition for the PD-L1 protein in lung cancer cells and high uptake in HCC287 lung micrometastases (>30% ID). The biokinetic profiles of 177Lu-DOTA-PD-L1-i and 225Ac-DOTA-PD-L1-i showed rapid blood clearance with renal and hepatobiliary elimination and no accumulation in normal tissues. 225Ac-DOTA-PD-L1-i produced a radiation dose of 5.15 mGy/MBq to lung micrometastases. In the case of 177Lu-DOTA-PD-L1-i, the radiation dose delivered to the lung micrometastases was ten times (43 mGy/MBq) that delivered to the kidneys (4.20 mGy/MBq) and fifty times that delivered to the liver (0.85 mGy/MBq). Therefore, the radiotherapeutic PD-L1-i ligands of 225Ac and 177Lu developed in this research could be combined with immunotherapy to enhance the therapeutic effect in various types of cancer.

Biokinetics, radiopharmacokinetics and estimation of the absorbed dose in healthy organs due to Technetium-99m transported in the core and on the surface of reconstituted high-density lipoprotein nanoparticles

The development of rHDL-radionuclide theragnostic systems requires evaluation of the absorbed doses that would be produced in healthy tissues and organs at risk. Technetium-99m is the most widely used radionuclide for diagnostic imaging, therefore, the design of theragnostic reconstituted high density-lipoprotein (rHDL) nanosystems labeled with Technetium-99m offers multiple possibilities.

OBJECTIVE

To determine the biokinetics, radiopharmacokinetics and estimate the absorbed doses induced in healthy organs by Technetium-99m transported in the core and on the surface of rHDL.

METHODS

Biokinetic and radiopharmacokinetic models of rHDL/[99mTc]Tc-HYNIC-DA (Technetium-99m in the core) and [99mTc]Tc-HYNIC-rHDL (Technetium-99m on the surface) were calculated from their ex vivo biodistribution in healthy mice. Absorbed doses were estimated by the MIRD formalism using OLINDA/EXM and LMFIT softwares.

RESULTS

rHDL/[99mTc]Tc-HYNIC-DA and [99mTc]Tc-HYNIC-rHDL show instantaneous absorption in kidney, lung, heart and pancreas, with slower absorption in spleen. rHDL/[99mTc]Tc-HYNIC-DA is absorbed more slowly in the intestine, while [99mTc]Tc-HYNIC-rHDL is absorbed more slowly in the liver. The main target organ for rHDL/[99mTc]Tc-HYNIC-DA, which is hydrophobic in nature, is the liver, whereas the kidney is for the more hydrophilic [99mTc]Tc-HYNIC-rHDL. Assuming that 925 MBq (25 mCi) of Technetium-99m, carried in the core or on the surface of rHDL, are administered, the maximum tolerated doses for the organs of greatest accumulation are not exceeded.

CONCLUSION

Theragnostic systems based on 99mTc-labeled rHDL are safe from the dosimetric point of view. The dose estimates obtained can be used to adjust the 99mTc-activity to be administered in future clinical trials.

High-Risk HPV with Multiple Infections Promotes CYP2E1, Lipoperoxidation and Pro-Inflammatory Cytokines in Semen of Asymptomatic Infertile Men

High-risk human papillomavirus (HR-HPV) infection, followed by chronic inflammation and oxidative stress, is a major risk factor of male infertility. In this study, we explored the potential impact of high-risk (HR) HPV genotypes in single infection (SI) and multiple infections (MI) that promote CYP2E1 expression, oxidative damage and pro-inflammatory cytokines, possibly contributing to sperm damage and male infertility. Semen samples from 101 infertile military men were studied. We analyzed seminal parameters, namely, HPV genotyping, cytochrome P450 2E1 (CYP2E1), oxidative stress biomarkers (total antioxidant capacity (TAC), catalase (CAT) and superoxide dismutase (SOD)), lipid peroxidation (LPO), 8-hydroxiguanosine (8-OHdG) and pro-inflammatory cytokines (IFN-γ, IL-1β, IL-4, IL-6 and IL-8). Eighty-one men (80.2%, 81/101) were positive for HPV infection, and MI-HR-HPV was higher than SI-HR-HPV (63% vs. 37%). HPV-52 was the most frequently detected type (18.5%), followed by HPV-33 (11.1%), and the most frequent combination of genotypes detected was HPV-33,52 (11.1%), followed by HPV-18,31 (6.2%). The group with infected samples presented lower normal morphology and antioxidant levels compared to non-infected samples. In concordance, the infected group showed high levels of LPO, IFN-γ, IL-1β, IL-4 and IL-6 and downregulation of CAT and SOD enzymes. Interestingly, changes in motility B, low levels of TAC, overexpression of CYP2E1, LPO and IL-8 levels were higher in MI-HR-HPV than SI-HR-HPV, suggesting that HPV infection promotes a chronic inflammatory process and a toxic and oxidative microenvironment, which increases with MI-HPV infections.

Comparison between 177Lu-iPSMA and 225Ac-iPSMA dosimetry at a cellular level in an animal bone metastasis model

The recent use of prostate-specific membrane antigen as a biological target have improved the theragnostic approach to prostate and other types of cancer. Radiopharmaceuticals based on PSMA inhibitors radiolabeled with beta emitters as Lutetium-177 have demonstrated remarkable efficacy and safety, however, their clinical evaluation have also shown that therapeutic response of bone located metastases is poorer than that presented by soft tissue lesions. These observations conducted to the development and study at different levels of PSMA-targeting alpha-particle therapy exhibiting effective and promising antitumor activity. However, some aspects of the use of alpha emitters such as cellular dosimetry should be considered before applying them safely. The aim of the present work was to compare and calculate the absorbed dose of 177Lu-iPSMA and 225Ac-iPSMA using an animal bone metastasis model and experimental data obtained from cellular fractionation. The number of disintegrations and the dose factors for the theragnostic iPSMA pair, molecule that can be radiolabeled with 177Lu or 225Ac, were determined based on MIRD methodology, and used to calculate the absorbed dose to cell nucleus. A five times difference between 225Ac-iPSMA and 177Lu-iPSMA average dose rate to the tumor was calculated, being 2.3 ± 0.037 for the first and 0.5 ± 0.018 Gy for the second, both for each activity unit (MBq) administered.

Proinflammatory and Oxidative Stress States Induced by Human Papillomavirus and Chlamydia trachomatis Coinfection Affect Sperm Quality in Asymptomatic Infertile Men

Background and Objectives: To investigate the effect of infection with human papillomavirus (HPV) or Chlamydia trachomatis (CT) and HPV + CT coinfection on sperm quality, inflammation, and the state of oxidative stress (OS) in asymptomatic infertile men. Materials and Methods: Semen samples from 84 asymptomatic military infertile men were studied. The polymerase chain reaction (PCR) was used for the molecular detection of HPV and CT. Semen parameters were analyzed according to the World Health Organization guidelines. Inflammation was evaluated by an IL-1β, IL-6, and IFN-γ enzyme-linked immunosorbent assay (ELISA) and OS by the quantification of lipid peroxidation (LPO), 8-hydroxydeoxyguanosine (8-OHdG), and total antioxidant capacity (TAC). Results: A total of 81 of the 84 (96.4%) samples were positives for the pathogens, with 55/81 (68%) being positive for HPV, 11/81 (13.5%) for CT, and 15/81 (18.5%) for HPV + CT coinfection. Seminal parameters were affected in the infected groups, including pH increases above the normal range in all groups. An abnormal sperm morphology was observed in the HPV and HPV + CT groups. Higher cytokine levels were detected in the HPV group and the highest IL-1β level was found in the HPV + CT group. No cytokines were detected in the CT group. High LPO and 8-OHdG levels were found in all groups with a lower TAC. Comparisons between groups showed the highest OS state was observed in the HPV group. Conclusions: High HPV infection or coinfection (HVP + CT) in these infertile men suggest compromising male fertility by inducing a proinflammatory state and OS. Infection with CT suggests an alteration of the state of OS by promoting an alkaline pH.

Evaluation of doxorubicin-induced early multi-organ toxicity in male CD1 mice by biodistribution of 18F-FDG and 67Ga-citrate. Pilot study

The search for methods that identify early toxicity, induced by chemotherapy, is urgent. Changes in the biodistribution of radiopharmaceuticals could give information on early toxicity. Ten-week-old CD1 male mice were divided into four groups. Two groups were administered a weekly dose of 5 mg/kg of doxorubicin hydrochloride (DOX) for 5 weeks and the control groups were administered saline solution. One week after the end of treatment, the biodistribution of ¹⁸F-FDG and ⁶⁷Ga-citrate were carried out, as was the quantification of plasma enzymes CK, CK-MB, LDH and AST. All enzymes were higher in the treated animals, but only significant (p < 0.05) in the case of CK-MB. ¹⁸F-FDG uptake increased in all organs of treated animals except retroperitoneal fat, being significant in spleen, brain, heart, liver, lung, kidney, and inguinal fat. ⁶⁷Ga-citrate had a more complex pattern. The uptake in the DOX group was higher in spleen, lung, kidney, testes, and gonadal fat, it did not change in brain, heart, and liver, and it was lower in the rest of the organs. It only showed significant differences in lung and pancreas. A thorough discussion of the possible causes that produced the change in biodistributions of both radiopharmaceuticals is included. The pilot study showed that both radiopharmaceuticals could identify early multi-organ toxicity induced by DOX. Although ¹⁸F-FDG seems to be better, ⁶⁷Ga-citrato should not be ruled out a priori. The detection of early toxicity would serve to adopt treatments that prevent its progression, thus improving patient's quality of life.

Femur absorptiometry changes determined by X-ray image segmentation in mice under experimental diabetes and ovariectomy

AIM

The aim of the present work was to determine if both ovariectomy (OVX) and type 2 diabetes mellitus (T2DM) can change X-ray absorptiometry until reach the osteoporosis condition.

RESULTS

The segmentation allowed us to quantitatively determine the X-ray absorption in the femurs of mice subjected to OVX, T2DM and both pathologies together.

CONCLUSIONS

The test subjects suffering from the mentioned pathologies separately or together, did not reach the osteoporosis condition when they were 30 weeks old.

The colors of adipose tissue and the relationship with irisin

Excess adipose tissue is considered one of the main causes of metabolic and cardiovascular diseases. Initially, the adipose tissue was considered the main lipid and energy storage of the organism. Subsequently it was discovered that adipose tissue had other functions such as endocrine, controlling different metabolic and immune processes. Currently, different types of adipose tissue are recognized. The white adipocyte represents the main energy reserve, on the contrary the brown adipocyte is responsible for the oxidation of lipids for thermogenesis. The beige adipocyte originates from the white adipocyte, by a process known as "browning", which leads to lipolysis and thermogenesis. The 3 previous types have recently joined the blue adipocyte, which has a role in liver retinoid homeostasis and the pink adipocyte that participates in lactogenesis and is present in the mammary gland of animals; its role is still unknown in humans. The newly identified hormone Irisin is secreted by the skeletal muscle and promotes browning of white to beige adipose tissue, thus favoring thermogenesis. Another interesting aspect of this hormone is that it represents a connection between muscle activity and lipolysis. The above suggests that Irisin may be the key in the prevention and treatment of obesity.

Effects of chronic immobilization stress on biokinetics and dosimetry of 67Ga in a murine model

The aim of this work is to determine the effect of chronic immobilization stress on kinetics and dosimetry of ⁶⁷Ga in a mouse model. A control group (CG) and a stress group (SG), each with 15 mice, were included in the study, and the latter group was subjected to a chronic immobilization stress model 2 h daily for 14 consecutive days. At day 13, ⁶⁷Ga-citrate was administered intraperitoneally (11.24 ± 0.44 MBq) to each mouse. Then, sets of three mice were obtained sequentially at 24, 36, 48, 60 and 72 h, in which the radionuclide activity was measured with an activity counter. The ⁶⁷Ga biokinetic data showed a fast blood clearance in the SG, with a mean residence time of 0.06 h. The calculated mean radiation absorbed doses were: liver (2.45 × 10^-03 Gy), heart (3.17 × 10^-04 Gy) and kidney (1.88 × 10^-04 Gy) in the SG. The results show that stress reduced weight gain by approximately 13% and also increased adrenal gland weight by 26%. On the other hand, chronic stress accelerates ⁶⁷Ga clearance after 24 h compared to normal conditions. It is concluded that murine organisms under chronic immobilization stress have higher gallium-67 clearance rates, decreasing the cumulated activity and absorbed dose in all organs.

Differences in the S value between male and female murine model for diagnostic, therapeutic and theragnostic radionuclides

The aim of this work was to calculate S values for ⁹⁹mTc, ⁶⁷Ga, ⁶⁸Ga, ¹⁸F, ²²³Ra, ¹⁶⁶Ho, ⁹⁰Y, ¹⁶¹Tb ¹³¹I and ¹⁷⁷Lu, using a mouse phantom (MOBY) standard and considering the anatomic sizes from males and females, the simulation of radiation transport was performed with GATE/Geant4 platform. This indicates that in the internal dosimetry the use of a customized geometry is relevant for each gender and a standard model is not a good choice.

TcVac1 vaccine delivery by intradermal electroporation enhances vaccine induced immune protection against Trypanosoma cruzi infection in mice

The efforts for the development and testing of vaccines against Trypanosoma cruzi infection have increased during the past years. We have designed a TcVac series of vaccines composed of T. cruzi derived, GPI-anchored membrane antigens. The TcVac vaccines have been shown to elicit humoral and cellular mediated immune responses and provide significant (but not complete) control of experimental infection in mice and dogs. Herein, we aimed to test two immunization protocols for the delivery of DNA-prime/DNA-boost vaccine (TcVac1) composed of TcG2 and TcG4 antigens in a BALB/c mouse model. Mice were immunized with TcVac1 through intradermal/electroporation (IDE) or intramuscular (IM) routes, challenged with T. cruzi, and evaluated during acute phase of infection. The humoral immune response was evaluated through the assessment of anti-TcG2 and anti-TcG4 IgG subtypes by using an ELISA. Cellular immune response was assessed through a lymphocyte proliferation assay. Finally, clinical and morphopathological aspects were evaluated for all experimental animals. Our results demonstrated that when comparing TcVac1 IDE delivery vs IM delivery, the former induced significantly higher level of antigen-specific antibody response (IgG2a + IgG2b > IgG1) and lymphocyte proliferation, which expanded in response to challenge infection. Histological evaluation after challenge infection showed infiltration of inflammatory cells (macrophages and lymphocytes) in the heart and skeletal tissue of all infected mice. However, the largest increase in inflammatory infiltrate was observed in TcVac1_IDE/Tc mice when compared with TcVac1_IM/Tc or non-vaccinated/infected mice. The extent of tissue inflammatory infiltrate was directly associated with the control of tissue amastigote nests in vaccinated/infected (vs. non-vaccinated/infected) mice. Our results suggest that IDE delivery improves the protective efficacy of TcVac1 vaccine against T. cruzi infection in mice when compared with IM delivery of the vaccine.

67Ga as a biosensor of iron needs in different organs: Study performed on male and female rats subjected to iron deficiency and exercise

The aim of the present study was to determine the iron needs in different organs and tissues using ⁶⁷Ga as a biosensor in males and females rats subjected to iron deficiency (ID) and voluntary exercise (EX). ⁶⁷Ga citrate was injected i.p. to female and male Wistar rats (n=5/sex/group). Groups: Control (sedentary conditions), Control+EX, ID and ID+EX. To determine the ⁶⁷Ga uptake, samples from the following regions of interest (ROIs) were extracted 12h post-injection: blood, liver, gonads, bone marrow, heart, adrenal glands, skeletal muscle, stomach, kidney, eyeball, sciatic nerve, small intestine and peritoneum. The total ⁶⁷Ga uptake was 412% higher in ID subjects than in control subjects, being 1011% higher in ID-males than ID-females. In ID-females, the ROIs with the greater ⁶⁷Ga uptake were blood, kidney and bone marrow, while in ID-males they were sciatic nerve, eyeball and adrenals, which demonstrates that the biodistribution differed between sexes in sedentary conditions but when subjected to EX, the biodistribution was similar in each sex group although females had a greater ⁶⁷Ga uptake. In ID+EX subjects, the ROIs that showed the highest uptake were sciatic nerve, eyeball and adrenal glands. Using ⁶⁷Ga as a biosensor, it is possible to identify the needs of iron that each organ requires to perform their functions in normal physiological conditions. In addition, a higher or lower ⁶⁷Ga uptake in a specific organ may indicate its malfunction or show damage.

Effects of astaxanthin in mice acutely infected with Trypanosoma cruzi

During Trypanosoma cruzi infection, oxidative stress is considered a contributing factor for dilated cardiomyopathy development. In this study, the effects of astaxanthin (ASTX) were evaluated as an alternative drug treatment for Chagas disease in a mouse model during the acute infection phase, given its anti-inflammatory, immunomodulating, and anti-oxidative properties. ASTX was tested in vitro in parasites grown axenically and in co-culture with Vero cells. In vivo tests were performed in BALB/c mice (4-6 weeks old) infected with Trypanosoma cruzi and supplemented with ASTX (10 mg/kg/day) and/or nifurtimox (NFMX; 100 mg/kg/day). Results show that ASTX has some detrimental effects on axenically cultured parasites, but not when cultured with mammalian cell monolayers. In vivo, ASTX did not have any therapeutic value against acute Trypanosoma cruzi infection, used either alone or in combination with NFMX. Infected animals treated with NFMX or ASTX/NFMX survived the experimental period (60 days), while infected animals treated only with ASTX died before day 30 post-infection. ASTX did not show any effect on the control of parasitemia; however, it was associated with an increment in focal heart lymphoplasmacytic infiltration, a reduced number of amastigote nests in cardiac tissue, and less hyperplasic spleen follicles when compared to control groups. Unexpectedly, ASTX showed a negative effect in infected animals co-treated with NFMX. An increment in parasitemia duration was observed, possibly due to ASTX blocking of free radicals, an anti-parasitic mechanism of NFMX. In conclusion, astaxanthin is not recommended during the acute phase of Chagas disease, either alone or in combination with nifurtimox.

Repeated restraint stress reduces the number of IgA-producing cells in Peyer's patches

The few reports that have analyzed the effects of stress on the immune cells of the intestinal mucosa or the functions of these cells have tended to focus on S-IgA levels in saliva, and these studies have shown contradictory results. The principal objective of this study was to analyze the effects of repeated restraint stress on the number and distribution of immune cells in Peyer's patches (PPs) as well as the effects of glucocorticoid and catecholamine administration on the same stress-related parameters. Upon analyzing the effect of repeated restraint stress on PPs, it was found that there was no modification in the morphological structure of the PPs but that restraint stress reduced the total number of lymphocytes and the number of CD8+ T cells, B cells, and plasma cells in PPs. Only at the site of PPs where IgA-producing plasma cells are most numerous (the dome) was a decrease found in this type of cell. These effects were due at least in part to the effect of glucocorticoids and catecholamines. Since IgA produced in PPs is a natural antibody that impedes bacterial infections, repeated stress may favor the entry of pathogens through the intestine.

Effects of restraint stress on NALT structure and nasal IgA levels

The effects of stress on the mucosal immune responses in inflammatory disorders of the gut, as well as on salivary and intestinal IgA levels are well known. However, its effects on the structure and function of the NALT have not yet been reported, and are examined in the present study. Balb/c mice were submitted to restraint stress for 3h per day during 4 or 8d. The immunohistochemistry and flow cytometric analysis revealed that repeated restraint stress (4 and 8d) decreased the percentage, compared to the control group, of CD3(+) and CD4(+) T cells, without affecting the percentage of CD8(+) T cells or B220(+) cells (B cells). The numbers of IELs (CD4(+) and CD8(+) T cells) were lower at 4d of stress and higher at 8d. IgA(+) cells in NALT and nasal IgA levels showed a similar pattern, being significantly lower at 4d of stress and significantly higher at 8d. In summary, repeated restraint stress altered the distribution and number of lymphocytes and IgA(+) cells in nasal mucosa, probably due to changes in norepinephrine and corticosterone levels.